Lola Toomey
email: lola.toomey@univ-lorraine.fr

Martin Bláha

Emilie Mauduit

Tatyana Vanina

Margot Baratçabal

Yannick Ledoré

Sami Vesala

Pascal Fontaine

Alain Pasquet

Thomas Lecocq
email: thomas.lecocq@univ-lorraine.fr

Simon Dellicour

Josephine Pegg

Zbigniew Kaczkowski

Jan Kouřil

Fabrice Teletchea

Toomey Lola

Lecocq Thomas

Bokor Zoltán

Espinat Laurent

Ferincz Árpád

Goulon Chloé

Vesala Sami

Baratçabal Margot

Barry Mamadou-Diouhe

Gouret Mélanie

Gouron Camille

Staszny Ádám

Mauduit Emilie

Speder Kevin

Thumerel Romain

Piatti Clémentine

Pasquet Alain

Fontaine Pascal

Andrzej Kapusta

Daniel Żarski

Frederik Buhrke

When behavioral geographic differentiation matters: inter-populational comparison of aggressiveness and group structure in the European perch

Keywords: Aggression -aquaculture -behavior -cannibalism -intraspecific differentiation -larvae -Perca fluviatilis -social structure Domestication, Fish culture, Intraspecific differentiation, Multi-function, Multitrait, Sustainability Geographic differentiation -Genetic diversity -Perca fluviatilis -Management -Production

Une thèse n'est possible que grâce à l'aide de nombreuses personnes. Ces quelques lignes ne suffiront pas à exprimer ma reconnaissance mais je souhaite témoigner de toute ma gratitude à l'ensemble des personnes qui ont contribué de près ou de loin à cette thèse, en espérant n'oublier personne.

Je tiens tout d'abord à remercier mes encadrants qui m'ont fait confiance et m'ont soutenue pour mener à bien cette thèse. Pascal, merci pour ta confiance et ton optimisme à toute épreuve, cela a été essentiel dans les moments plus difficiles de cette thèse. J'ai beaucoup apprécié ta bonne humeur constante et tes précieux conseils tout au long de ce travail. Merci aussi pour ton aide pendant l'échantillonnage, conduire jusqu'en Hongrie ou Allemagne n'était pas tâche facile, mais avec des gâteaux ça passe plus vite ! Thomas, un grand merci la grande aide que tu m'as accordée depuis le début de cette thèse. Malgré toutes les fois où j'arrivais dans ton bureau à l'improviste (au moins « nonante » fois), tu m'as toujours accordé du temps pour m'écouter et éclaircir les concepts qui me paraissaient flous. Merci pour la rigueur que tu as su me transmettre et pour tes avis souvent très « cashs » mais qui m'ont finalement beaucoup aidée à m'améliorer, tant à l'oral qu'à l'écrit ! Merci pour m'avoir fait confiance pour l'enseignement, ces cours m'ont beaucoup apporté (même si niveau « insectes » je n'y connais toujours rien !).

I would like to particularly thank the members of my jury for accepting to evaluate this work. Firstly, I would like to thank Patrick Kestemont and Costas Tsigenopoulos for accepting to be the referees for this thesis despite their busy schedules. Quiero también agradecer a Alicia Estevez por aceptar evaluar este trabajo. Enfin, merci à Edwige Quillet qui a accepté d'être examinatrice de cette thèse malgré son emploi du temps chargé. Merci d'avoir suivi l'évolution de ce travail à travers les réunions de comité de thèse et pour tes conseils avisés qui m'ont (j'espère !) permis d'être davantage rigoureuse dans ce travail. Je voudrais également remercier les autres membres de mon comité de thèse qui ont contribué à la réflexion de ce projet. Merci à Nicolas Poulet d'avoir apporté un regard extérieur sur ce travail et pour m'avoir conseillé à chaque comité de thèse. Un grand merci à Simon Dellicour pour ses nombreux conseils et son aide pour plusieurs des chapitres de cette thèse. Ton aide pour de nombreuses analyses et tes relectures attentives ont été très précieuses pour accroître la qualité des papiers. Enfin, merci à Fabrice Teletchea pour m'avoir conseillé tout au long de la construction des bioessais et du choix des traits. Ton expertise m'a été très utile, notamment dans les premières années de ce travail.

Cette thèse n'aurait pas pu avoir lieu sans l'aide des très nombreux collaborateurs. Construire un réseau n'a pas été toujours facile mais cela m'a permis de faire de très belles rencontres. Cette thèse a d'abord débuté par l'envoi de très nombreux mails pour collecter des échantillons de nageoires. Ils sont trop nombreux pour les citer mais un très grand merci aux 50 collaborateurs qui m'ont répondu et envoyé des échantillons. I would like to thank Martin Blaha for welcoming me in his laboratory twice during my PhD, which allowed me to perform all the genetic lab work. Thank you for sharing your knowledge on microsatellite analyses and for our collaboration on our shared papers. This work would not have been Other Survival rate, metabolic rate, ATPase activity, thermal tolerance, tolerance to low ammonia and low oxygen, saltwater/freshwater tolerance stress response and recovery Reproduction Gonadosomatic index, fertilization rate, egg diameter/length/weight, hatching rate, fecundity, age/size at sexual maturation, spawning time, spawning rate, ovulation success Lakes Molnbyggen and Djursjön, Sweden

possible without the help with collecting perch egg ribbons in the different studied lakes. Despite the lack of luck and the difficulty, we managed to collect samples from seven lakes so I am very grateful to: Bokor Zoltan, Ferincz Arpad, Staszny Adam, Fodor Ferenc (Hungary), Katja Kulo, Pasi Ala-Opas, Sami Vesala (Finland), Chloé Goulon, Laurent Espinat, Laurent Rachet et le club de plongée d'Aix les bains (France), Andrzej Kapusca, Daniel Zarski (Poland), and Frederik Buhrke (Germany).

Je remercie également l'ensemble des personnes de l'équipe DAC pour ces années passées à vos côtés. Un grand merci à Dominique pour son sourire et pour m'avoir donné l'opportunité d'enseigner tout au long de ma thèse; à Alain pour nos longues discussions, ton expertise en comportement, tes avis constructifs et ton humour à toute épreuve (la génétique l'emportera, tu verras); à Bérénice pour ta bonne humeur et nos échanges; à Marielle pour tes sourires matinaux, ta rigueur pour la qualité et ta bienveillance; à Daniel pour ta gentillesse, ton sourire et ton amour du sud; à Joëlle pour tes bonjours souriants tous les jours et ton aide plus que précieuse pendant les expérimentations; à Yannick pour nos midis animés, les légumes de ton jardin, ton aide pour l'échantillonnage (on se souviendra de notre excursion en Finlande) et ton aide pour mes expérimentations; à Sylvain pour m'avoir formée pour faire des dosages ELISA et pour ton regard critique lors des réunions scientifiques; à Patricia pour ta bienveillance et ton sourire, merci de m'avoir aidée (sans râler !) à chaque fois que j'étais perdue dans les eaux troubles des bons de commande ou des ordres de mission. Je n'oublie pas l'ensemble des membres de QUALIVIE et MRCA qui m'ont très bien accueillie à mon arrivée, particulièrement Guido Rychen pour m'avoir accueillie dans le laboratoire et Catherine Larrière pour ta gentillesse et ton aide pour toutes les démarches administratives. Un merci aussi à tous mes collègues d'enseignement, Sandra, Sabine, Noémie, Marine, Nadège, Hélène, François, Claire, Marie, pour leur bonne humeur, leur partage de connaissances et leur aide.

Un merci également à la région Grand Est pour le projet DomPop qui a financé une partie de ma thèse ainsi qu'Aquaexcel qui a permis de financer une partie des bioessais en collaboration avec l'Université de Bohème du Sud.

Le travail était conséquent et c'est pourquoi je remercie grandement mon « armée » de stagiaires comme tout le monde l'appelle: Emilie, Romain, Vicheka, Margot, Anaïs, Louis, Nicolas, Kévin, Mamadou, Mélanie, Camille, Iris et Clémentine. L'encadrement m'a énormément apporté et sans vous, sans votre investissement et votre bonne humeur malgré votre présence certains weekends et jours fériés, tout ce travail n'aurait pas pu être possible. Merci.

La thèse serait beaucoup moins drôle sans les amis. Un grand merci à Jennifer pour ton soutien indéfectible pendant toute la thèse, tes conseils et notre amour partagé pour la Kasteel rouge. Ton sourire et ton réconfort m'ont beaucoup aidée ! Merci aussi à Geoffrey pour ton humour et ta bonne humeur, je n'oublierai jamais tes blagues à double sens ! Imen, que dire, tu m'as aussi beaucoup aidée tout au long de cette thèse, ta patience est légendaire et ton sourire des plus rassurants. Merci pour ta grande aide pour les modèles statistiques, pour ta présence dans les moments de doute, merci simplement pour ton amitié. Merci aussi à Alois pour ta bonne humeur et pour avoir supporté nos conversations de fille interminables. Merci à Tatiana pour ton sourire et ta bienveillance, ton aide pour l'enseignement et pour nos petits repas. Merci à François pour tes partages musicaux et tes bons petits plats maison ! Merci à Maud pour ta bonne humeur et tes photos sublimes de Norvège ! Merci à JB pour sa bonne humeur et son humour. Merci à Brian pour ta gentillesse malgré le fait qu'on ne se soit pas vu longtemps. Merci à Amine pour ta gentillesse et tes plats « cuisinés » du midi. Merci à Taina pour ton soutien tout au long de cette thèse et ton mix français/portugais qui a occasionné de nombreux fous rires. Leyla, thank you for being my work roomie and for your support. I wish you all the best for the end of your PhD thesis. Nellya, tu es arrivée il y a peu, je ne comprends pas tout sur la complémentarité des espèces mais je te souhaite bon courage pour la thèse ! Je te remercie pour ta grande gentillesse et ton écoute. Enfin Sonia, merci pour ton soutien durant cette fin de thèse. Merci de m'avoir trainée à la salle de sport, de m'avoir fait sortir de ma grotte dans ma phase rédactionnelle, de partager mon amour pour la bière blanche, de m'avoir encouragée à finir mon manuscrit. Ton amitié est précieuse et ce n'est que le début. Merci aussi à mes amis les plus proches qui m'ont soutenue tout au long de cette thèse : Surya, Perrine, Clémentine, Fred, Maylis, Valentin, Marion, Maxime, Gaëlle et Sonia. Sans vous, ma vie serait vraiment triste ! Thank you Daniel for your kindness and your friendship. I also would like to thank Rob. Thank you for your friendship and your smile each time I see you, I will definitely spend more time in the Netherlands from now on.

Ma famille a aussi été essentielle dans cette thèse et un soutien majeur. Gracias a Lorelay, Alberto, Lorena, Carlos, Laura y Roberto por su apoyo y su simpatía. Estoy muy contenta conoceros y ser parte de vuestra familia. Muchas gracias a todos. Thank you aunt Siobhan and Joe for following my work and supporting me. Merci Mamie pour tes appels et encouragements tout au long de cette thèse, enfin c'est fini ! Merci aussi à mes frères et soeur pour leur soutien tout au long de cette thèse : Jamie pour avoir essayé de comprendre mon sujet et m'avoir envoyé des magnifiques photos de voyage alors que j'étais coincée à rédiger ma thèse, futur Dr. Tim pour ton humour et nos débats animés et Lucie pour tes messages encourageants et ta gentillesse. Papa, maman, merci pour votre soutien tout au long de cette thèse, pour m'avoir toujours encouragée et avoir cru en moi, même quand je partais à l'autre bout du monde, merci pour les colis « surprise » et vos relectures de cette thèse (surtout toi papa, ce n'était pas un cadeau !). Je vous aime. Merci à Cirilla d'avoir supporté les nourrissages aux horaires décalés selon mes heures variables de sortie du bureau. Last but not least, thank you Carlos for being there all along this PhD thesis. You dragged me in, so you always said you had to help me reach the end. I cannot say how much you helped all along this work, reading my papers, listening to my presentations, supporting me during congresses, gluing pipes, reading the whole manuscript, memeing my thesis, always telling me to keep going and to stay optimistic. Words will not be sufficient to express my gratitude. Te amo. Ahora podemos empezar nuestra nueva vida juntos… I would like to dedicate this PhD thesis to my grandpa. You could not see the end of it, but this work is for you… [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

LIST OF TABLES

Table 3: Characteristics which can facilitate or limit the animal population domestication and subsequent production (according to [START_REF] Webber | Criteria for candidate species for aquaculture[END_REF][START_REF] Tennessen | Traits relevant to the domestication of herbivores[END_REF][START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Price | Animal Domestication and Behavior[END_REF][START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]Zeder 2012a).

Table 4: Examples of characteristics which favor fish domestication and production [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF], associated to examples of wild geographic differentiation for these characteristics.

Table 5: Examples of the main traits/parameters investigated in the geographic differentiation studies referenced.

Table 6:

Examples of studies highlighting trait differentiation between Salmo salar allopatric populations. Remark: These studies did not all perform an evaluation on all 41 populations but rather on a subset of populations.

Table 7:

Examples of variation of the spawning period and temperature at spawning between allopatric populations of European perch. Adapted from [START_REF] Fontaine | Broodstock Management and Control of the Reproductive Cycle[END_REF]. NR: Not Reported.

Table 8: Studies highlighting Perca fluviatilis geographic differentiation in aquaculture conditions. Remark: Only traits for which a geographic differentiation was shown are reported here. Rivers, lakes, brackish waters, and ponds are indicated by R, L, B, and P, respectively. [START_REF] Alix | An alternative developmental table to describe nonmodel fish species embryogenesis: application to the description of the Eurasian perch (Perca fluviatilis L. 1758) development[END_REF]. O1: first phase of organogenesis (from the first cell differentiation to the first heart beatings; 2-4 days post-fertilization); O2: second phase of organogenesis (from the first heart beatings to the differentiation of the organs associated to the digestive system; 4-7 days post-fertilization).

Table 13: Univariate statistics results on differentiation between populations and prospective units (PU) for the different traits studied.  indicates a statistically significant differentiation (p-value<0.05), a cross (x) indicates a lack of statistically significant differentiation (p-value>0.05). Diff corresponds to differentiation. Mean value corresponds the mean across all populations/PUs, minimum to the lowest value, maximum to the maximal value.

Table 14: Summary of MRDM-CA and Mantel results for phase II. Best proxies correspond to proxies with a unique contribution > 1%. * indicates a significant R 2 (p-value<0.05).

Table 15: Summary of MRDM-CA and Mantel results for phase I associated to the weight coefficients obtained in the fourth chapter.

Table 16: Calculation of the aquaculture potential score using formulas A and B and data from the fourth chapter. [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF].

LIST OF FIGURES

Numbers correspond to populations studied (the Siberian population is not represented here).

The white regions correspond to the areas which were glaciated during the last glaciations.

From [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]. CONTEXT: Domestication and intraspecific differentiation 1. Domestication: definition(s) and process 1.1 Definition(s) The domestication of organisms is one of the most essential developments in human history and it has triggered major changes leading to mankind's current state. Across the literature, domestication is seen as a relationship, often mutualistic, between humans and plant or animal populations. Even though some authors use the domestication term to describe non-human interactions (e.g. fungus growing ants [Insecta, Hymenoptera, Formicidae, Atta sp.]; [START_REF] Mueller | The evolution of agriculture in ants[END_REF], the term in this work is used within an anthropocentric context. Domestication is still a widely debated concept given the wide range of alternate definitions referenced in literature (Table 1). This results from (i) disagreements regarding on which actor of the relationship the emphasis should be placed (i.e. human and/or animal/plant involved in the domestication process), (ii) its complexity due to the involvement of both biological and social notions, and (iii) the narrowing of some definitions to a particular species/species group [START_REF] Russell | The wild side of animal domestication[END_REF][START_REF] Zeder | Core questions in domestication research[END_REF]. For this work, domestication is defined as the process in which a wild population is bred in a human-controlled environment and this population evolves across generations from its wild ancestor, in ways making it more useful to humans who increasingly control their reproduction and food supply [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]). This definition is integrative and allows to combine concepts from different previous definitions. The human control on the culture environment can be more or less important (e.g. weaker control in extensive production systems such as open ponds or ranching; stronger control in intensive production systems such as indoor recirculating aquaculture systems or factory farms). Domestication is not performed on all populations of a species but rather on specific population(s) of a given species.

Domestication steps

Domestication is a difficult, long, and continuous process which can be divided in five steps (Table 2; called "domestication levels"), depending on the degree of control over the life cycle and the level of gene flow with wild conspecifics [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]. This classification has been initially developed for fishes [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF] but has been further applied to other taxa [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]. The first step corresponds to the acclimatization process, when a wild population is transferred from the wild to a human-controlled environment. The next domestication steps are defined by an increasing human-control over the life cycle and a decrease of the use of wild counterparts to replenish farmed stocks. In this way, step two refers to the stage in which a part of the life cycle is controlled but there are still major bottlenecks preventing the completion of the life cycle; step three corresponds to the full completion of the life cycle but wild individuals are still collected in the wild to supply farmed stocks; and finally step four refers to when the entire life cycle is closed in captivity without further input from wild captures. The last stage of domestication (step five) corresponds to the development of selective breeding (or artificial selection) programs, which aim at intentionally modifying Source Domestication definition [START_REF] Price | Behavioral aspects of animal domestication[END_REF] « Process by which a population of animals becomes adapted to man and to the captive environment by genetic changes occurring over generations and environmentally induced developmental events reoccurring during each generation » Diamond (1997a) « Domestication involves wild animals' being transformed into something more useful to humans » [START_REF] Weisdorf | From foraging to farming: Explaining the Neolithic Revolution[END_REF] « Unintentional process by which human intervention, selection and replanting (i.e., environmental manipulation) eventually gave rise to strains of plants and animals that depended upon human assistance for their survival and upon which humans in turn depended sustenance » [START_REF] Bilio | Controlled reproduction and domestication in aquaculture -The current state of the art, Part I -IV[END_REF] « Gradual adaptation of an organism to living conditions that are determined by some form of human intervention » [START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF] « Permanent genetic modification of a bred lineage that leads to, among other things, a heritable predisposition toward human association » Zeder (2012a) « Sustained multi-generational mutualistic relationship in which humans assume some significant level of control over the reproduction and care of a plant/animal in order to secure a more predictable supply of a resource of interest and through which the plant/animal is able to increase its reproductive success over individuals not participating in this relationship » [START_REF] Jensen | Behavioral Genetics and Animal Domestication[END_REF] « Process whereby populations of animals change genetically and phenotypically in response to the selection pressure associated with a life under human supervision » Zeder (2015) « A coevolutionary, mutualistic relationship between domesticators and domesticates » [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF] « Process in which populations are bred in man-controlled environment and modified across succeeding generations from their wild ancestors in ways making them more useful to humans who control, increasingly during the process, their reproduction and food supply » organisms based on desirable traits [START_REF] Vaughan | From crop domestication to super-domestication[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

Domestication is therefore a continuum and populations can move forward or backward along the process.

Table 2: Domestication levels according to [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

Historical context of domestication

During the Upper Paleolithic era, modern humans (Mammalia, Primates, Hominidae, Homo sapiens) were composed by hunter-gatherer communities. The primary subsistence strategy was relying on hunting, fishing, and gathering (Diamond 1997b). The premises of domestication of animal and plant populations started at least 15 000 years ago with the domestication of wolf populations, which correspond to the ancestors of modern dog (Mammalia, Carnivora, Canidae, Canis lupus) population(s) [START_REF] Braastad | Behavior of dogs and cats[END_REF].

Nevertheless, it is later, during the Neolithic period, that human lifestyle radically changed with the rise of agriculture and the shift from the hunter-gatherer lifestyle to farmers [START_REF] Vigne | The origins of animal domestication and husbandry: A major change in the history of humanity and the biosphere[END_REF]. The oldest traces of agriculture activity were found in the Fertile Crescent about 10 000 years ago, notably through the culture of vegetal species, which resulted from the sowing of these species (Diamond 1997a;[START_REF] Lev-Yadun | The Cradle of Agriculture[END_REF]. Hunter-gatherers initiated the domestication of numerous cereals, such as wheat (Angiosperms, Poales, Poaceae, Triticum sp.) and barley (Angiosperms, Poales, Poaceae, Hordeum spontaneum) in the Middle East, as well several other annual plants (Diamond 1997a[START_REF] Diamond | The Local Origins of Domestication[END_REF]. Domestication of animal populations, particularly terrestrial mammals which are essential in modern agriculture, overall developed later [START_REF] Bruford | DNA markers reveal the complexity of livestock domestication[END_REF][START_REF] Vigne | The origins of animal domestication and husbandry: A major change in the history of humanity and the biosphere[END_REF]. Through time, sedentary farmer societies replaced hunter-gatherers' societies, independently in several geographic locations. This transition is referred as the Neolithic revolution [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF].

The transition to the farming lifestyle has provided a selective advantage to humans, notably through the food resource securing, which allowed them to progressively disseminate their lifestyle (but see also some negative consequences such as health decline or increased spread Domestication level Description 1 "First trials of acclimatization to the culture environment" 2 "Part of the life cycle is completed in captivity, but several important bottlenecks still exist in others (e.g. reproduction, larval rearing)" 3 "The entire life cycle is closed in captivity but with wild inputs" 4 "The entire life cycle is closed in captivity without wild input, but no selective breeding programs is used" 5 "Selective breeding programs" of pathogens; Latham 2013). As a point of comparison, half of a hectare of land culture can nourish ten to 100 times more individuals than hunter-gatherers (Diamond 1997). Therefore, the Neolithic revolution corresponds to a major turning point in human history and led to deep shifts in the evolution, ecology, and demography of humans (e.g. human settlement, diversification of techniques, outbreak of structured human societies; [START_REF] Vigne | The origins of animal domestication and husbandry: A major change in the history of humanity and the biosphere[END_REF][START_REF] Gepts | Biodiversity in Agriculture Domestication, Evolution, and Sustainability[END_REF]. The triggering factors which lead human populations to abandon the hunter-gatherer lifestyle to start agriculture are still under investigation but several (sometimes complementary) hypotheses have been raised (e.g. population growth and resource decline, climate, social changes; [START_REF] Price | Social Inequality at the Origins of Agriculture[END_REF][START_REF] Gupta | Origin of agriculture and domestication of plants and animals linked to early Holocene climate amelioration[END_REF][START_REF] Vigne | The origins of animal domestication and husbandry: A major change in the history of humanity and the biosphere[END_REF].

So far, examples of domestication for food purposes have been highlighted. However, it must also be underlined that food provisioning was not the only benefit from domestication.

Indeed, populations which were domesticated have also been used for other purposes:

protection, basic materials, transport, and later on as biological control agents, laboratory models, for entertainment, or for ornamental purposes (Diamond 1997a[START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Price | Behavioral development in animals undergoing domestication[END_REF][START_REF] Price | Animal Domestication and Behavior[END_REF][START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF][START_REF] Santana | Atelerix albiventris (Erinaceomorpha: Erinaceidae)[END_REF][START_REF] Moorhead | Development of captive breeding techniques for marine ornamental fish: a review[END_REF][START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]). In addition, these domestication purposes are not independent since some conspecific populations have been used for different outputs (e.g. wool production and meat).

Humans have domesticated/attempted to domesticate numerous terrestrial species populations [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF], in several instances without an initial intentional action to domesticate.

Different domestication pathways have been suggested (Zeder 2012b;[START_REF] Larson | The evolution of animal domestication[END_REF]: (i) the commensal pathway for which there is no initial intention to domesticate but in which wild populations got benefits from staying in the human niche (e.g. dog domestication;

Larson and Fuller 2014), (ii) the prey pathway in which the initial motivation is not domestication but food provisioning (perhaps because of local stocks depletion of hunted preys) and in which hunting strategies evolved over time to game management/keeping strategies and later on to herd-management strategies (e.g. large terrestrial mammals domestication, Zeder 2012a), and (iii) the direct pathway when there is a deliberate domestication initiated by humans towards a wild population which is the most common pathway for modern populations under domestication (e.g. golden hamsters, fish species, most insects; [START_REF] Fritzsche | Differences in reproductive success between laboratory and wild-derived golden hamsters (Mesocricetus auratus) as a consequence of inbreeding[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]). However, these pathways are not independent, and domestication can result from the involvement of several pathways [START_REF] Larson | The evolution of animal domestication[END_REF]. In the frame of this work, the focus was placed on the direct pathway, more particularly for food provisioning purposes.

Overall, domestication efforts for food purposes have been focused on populations from a few species [START_REF] Gepts | Biodiversity in Agriculture Domestication, Evolution, and Sustainability[END_REF]. Indeed, four cereal crops (rice, maize, potatoes, and wheat) provide around two-thirds of total human needs [START_REF] Troell | Does aquaculture add resilience to the global food system?[END_REF]. Similarly, land agriculture rests on solely five major species which display a very high breed diversity [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Teletchea | Qu'est-ce qu'un poisson domestique ? Implications pour le développement futur de l'aquaculture[END_REF]. Overall, modern human diet is based on a few species (0.08% of terrestrial plants and 0.0001% of animal terrestrial species described nowadays), which were domesticated these last 12 000 years [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Duarte | Rapid domestication of marine species[END_REF]) and terrestrial species are nowadays considered for domestication for other purposes than food provisioning. On the contrary, in aquaculture (i.e. production of aquatic species), domestication processes started overall recently and numerous species have been/are considered for the food market. Yet, the aquaculture production still relies on a low number of species (see Introduction).

Domestication: a long and difficult process

Domestication is long and difficult and often results in unfruitful attempts [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]. Domestication attempts and subsequent production can fail due to technical limitations, socio-economic constraints, or intrinsic species features (i.e. single feature or quantifiable measurement of an organism; [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF]. Analyzing previous success-stories or failures, several features can be highlighted as limiting or facilitating the domestication process and subsequent production (see Table 3 for animal species). These features include both intrinsic biological traits (essential for domestication) and socio-economic characteristics (relevant for production). In this way, for instance, low growth rate, high aggressiveness, poor market value, and low disease resistance characterize poor candidates for animal domestication and subsequent production (Table 3) while numerous species fruitfully domesticated and produced present the opposite characteristics. In addition, depending on the domestication system, the importance of some of these characteristics is going to vary. For instance, sensitivity to environmental changes is essential in outdoor culture [START_REF] Ficke | Potential impacts of global climate change on freshwater fisheries[END_REF][START_REF] Altieri | Agroecology and the design of climate changeresilient farming systems[END_REF] while the tolerance to conspecifics is important in intensive production [START_REF] Bouissou | Le comportement social des bovins et ses conséquences en élevage[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]). This implies that not all species are suitable to start new domestication processes in every human-controlled environment.

Table 3: Characteristics which can facilitate or limit the animal population domestication and subsequent production (according to [START_REF] Webber | Criteria for candidate species for aquaculture[END_REF][START_REF] Tennessen | Traits relevant to the domestication of herbivores[END_REF][START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Price | Animal Domestication and Behavior[END_REF][START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]Zeder 2012a).

Many domestication processes still rely on trial and error approaches, which are time and money consuming. Therefore, there is a need to rationalize new domestication processes. Yet, the analysis of these favoring/limiting characteristics can be useful to point out poor and good candidates for domestication and subsequent production and avoid those expressing numerous limiting characteristics which would lead to potentially unfruitful domestication attempts. In this perspective, several methods have been developed at the inter-specific level to identify candidate species with high agriculture/aquaculture potential (i.e. quantification of how much the expression of all key traits [biological and socio-economical]/functions is favorable for domestication and subsequent production). For instance, DeHaan et al. ( 2016) developed a pipeline approach for grain crop domestication. This approach relies on the fact that wild crops have traits limiting their domestication and/or production while others have characteristics making them easier/faster to domesticate and produce (e.g. easiness to harvest, high yield, high nutrition and quality attributes). The approach focuses on screening the biodiversity and identifying among all wild candidates the species with the highest potential(s) for agriculture. However, these approaches neglect a part of the wild biodiversity which could facilitate the domestication and subsequent production of new candidate species:

the wild geographic differentiation.

Geographic differentiation: its potential usefulness for domestication and production

4.1 What is geographic differentiation?

Except for clonal species, all conspecific individuals are genetically and phenotypically unique. Intraspecific differentiation corresponds to the differentiation found either withinpopulations (at the individual level) or between conspecific populations (inter-populational level). A large part of the wild intraspecific differentiation is linked with the geographic origin of populations: this refers to the geographic differentiation, which is considered here as the differentiation between allopatric (i.e. geographically distinct) conspecific populations [START_REF] Mayr | Systematics and the Origin of Species[END_REF][START_REF] Mayr | Animal species and evolution[END_REF]. Geographic variation has been investigated for a wide range of taxa [START_REF] Mayr | Animal species and evolution[END_REF]. Indeed, it is well known in the wild for plants [START_REF] Li | Latitudinal variation in plant size and relative growth rate in Arabidopsis thaliana[END_REF][START_REF] Więski | Latitudinal variation in resistance and tolerance to herbivory of a salt marsh shrub[END_REF], fishes [START_REF] Blanck | Large-scale intraspecific variation in life-history traits of European freshwater fish[END_REF][START_REF] Yeates-Burghart | Latitudinal variation in photoperiodic response of the three-spined stickleback Gasterosteus aculeatus in western North America[END_REF], insects [START_REF] Araki | Molecular and behavioral differentiation among Brazilian populations of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae)[END_REF][START_REF] Chen | Variation in cold hardiness of Liriomyza huidobrensis (Diptera: Agromyzidae) along latitudinal gradients[END_REF], reptiles [START_REF] Sperry | Latitudinal variation in seasonal activity and mortality in ratsnakes (Elaphe obsoleta)[END_REF][START_REF] Du | Latitudinal and seasonal variation in reproductive effort of the eastern fence lizard (Sceloporus undulatus)[END_REF], mammals [START_REF] Pitman | Three forms of killer whales (Orcinus orca) in Antarctic waters[END_REF][START_REF] Delarue | Geographic variation in Northwest Atlantic fin whale (Balaenoptera physalus) song: Implications for stock structure assessment[END_REF], and birds [START_REF] Tremblay | Geographic variation in the foraging behavior, diet and chick growth of rockhopper penguins[END_REF][START_REF] Mainwaring | Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment[END_REF].

Geographic differentiation: how?

Geographic differentiation is shaped by inter-population divergence processes, resulting from distinct demographic histories, random genetic drift, and/or local adaptations (Box 1; [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF][START_REF] Hewitt | Speciation, hybrid zones and phylogeography -Or seeing genes in space and time[END_REF]). Past demographic events (e.g. distribution range shifts triggered by climate cycles; [START_REF] Bernatchez | Comparative phylogeography of Nearctic and Paleartic fishes[END_REF]Hewitt 2004b) and barriers (e.g. geographic, climatic, behavioral, temporal) are important factors shaping geographic differentiation. Indeed, they can limit/prevent gene flow between gene pools. The limitation of gene flow and differences in selective pressure regimes can lead to genetic divergence between these gene pools though random processes (i.e. genetic drift, random mutations) and/or local adaptations (i.e. process increasing the frequency of traits which favor fitness in a given environment, [START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF][START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Losos | Adaptation and diversification on islands[END_REF]. Local adaptation can shape population specificities in numerous traits, including key features for domestication and commercial production. Geographic differentiation can ultimately lead to allopatric speciation in the absence of gene flow.

Box 1:

Examples highlighting processes leading to geographic differentiation in key trait(s)

Two alternate non-exclusive processes shaping geographic differentiation between two gene pools are exemplified: (i) local adaptation and (ii) divergences through random processes (genetic drift and mutation). P1 and P2 correspond to alternative phenotypes. Phenotypic differentiation can implicate both genetic and epigenetic factors. Any trait, morphological, physiological, behavioral, or ecological may vary geographically [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Foster | The geography of behavior: an evolutionary perspective[END_REF]). However, interestingly, geographic differentiation was highlighted in the literature for several characteristics which can facilitate or limit domestication and subsequent production (Table 3). For instance, a wild geographic differentiation was highlighted for growth rate (e.g. [START_REF] Chauvaud | Variation in size and growth of the great scallop Pecten maximus along a latitudinal gradient[END_REF], aggressiveness (e.g. [START_REF] Wiltenmuth | Geographical variation in agonistic behavior in a ring species of salamander, Ensatina eschscholtzii[END_REF], sensitivity to environmental changes (e.g. [START_REF] Räsänen | Geographic variation in acid stress tolerance of the moor frog, Rana arvalis. I. Local adaptation[END_REF],

reproductive behavior (e.g. [START_REF] Herring | Sexual incompatibility and geographical variation in mate recognition systems: Tests in the salamander Desmognathus ochrophaeus[END_REF], food consumption (e.g. [START_REF] Lindgren | Proximate causes of adaptive growth rates: Growth efficiency variation among latitudinal populations of Rana temporaria[END_REF], disease resistance (e.g. Owen- [START_REF] Hasselquist | Latitudinal variation of immune defense and sickness behavior in the white-crowned sparrow (Zonotrichia leucophrys)[END_REF], or survival rate (e.g. [START_REF] Blanchette | Geographic variability in form, size and survival of Egregia menziesii around Point Conception, California[END_REF]. This highlights that there could be an interest in considering wild geographic differentiation in order to find wild populations which could facilitate domestication and subsequent production, as suggested recently for seaweed culture [START_REF] Valero | Perspectives on domestication research for sustainable seaweed aquaculture[END_REF]. Indeed, picking in the wild phenotypes which present multiple favoring and few limiting characteristics would optimize chances of success for a given domestication trial.

A few success stories have shown that considering population specificities can lead to fruitful domestication and production. For instance, the buff-tailed bumblebee (Insecta, Hymenoptera, Apidae, Bombus terrestris) provides a good example of the successful use of wild geographic differentiation in a domestication/production process. This bumblebee is used for greenhouse pollination [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF] and displays a large geographic differentiation in several commercially important traits involved in its ability to be industrially produced and pollinate crops [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF][START_REF] Kwon | Bombiculture: A fascinating insect industry for crop pollination in Korea[END_REF]Lecocq et al. 2016b, a). At the beginning of the buff-tailed bumblebee production, European breeders tried to successively rear several wild subspecies [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF]. Within a fairly short time, one subspecies proved to have superior characteristics for commercial use (i.e. largest colonies, high pollination efficiency, low aggressiveness; Box 2). This subspecies allowed to develop a fruitful production (Lecocq et al. 2016b). Even though domestication was already initiated and production running, this example shows how the consideration of wild geographic differentiation helped to facilitate domestication and production.

At more advanced stages of domestication, geographic differentiation was considered for the European honeybee (Insecta, Hymenoptera, Apidae, Apis mellifera) production since non-African populations presented characteristics facilitating beekeeping (e.g. survival in temperate regions, low aggressiveness; [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]. Other examples can be found in land agriculture (Box 3). Indeed, geographic differentiation in commercially important traits (e.g. fruit mass, flesh depth, tree height, flesh fibrosity) was investigated between wild allopatric populations in the "ideotype" research for new tree domestication programs [START_REF] Leakey | Tree Domestication in Agroforestry: Progress in the Second Decade[END_REF]. This was performed for several species, such as Ricinodendron heudelotii (Angiosperms, Malpighiales, Euphorbiaceae; [START_REF] Mpeck | Strategies for the domestication of Ricinodendron heudelotii: evaluation of variability in natural populations from Cameroon[END_REF], Santalum austrocaledonicum (Angiosperms, Santalales, Santalaceae; [START_REF] Page | Geographic and Phenotypic Variation in Heartwood and Essential-Oil Characters in Natural Populations of Santalum austrocaledonicum in Vanuatu[END_REF], Adansonia digitata (Angiosperms, Malvales, Malvaceae ; [START_REF] Jensen | A research approach supporting domestication of Baobab (Adansonia digitata L.) in West Africa[END_REF], Sclerocarya birrea (Angiosperms, Sapindales, Anacardiaceae ; Leakey et al. 2005a, b), and Irvingia gabonensis (Angiosperms, Malpighiales, Irvingiaceae; [START_REF] Ladipo | Domestication of the bush mango (Irvingia spp.): some exploitable intraspecific variations in west and central Africa[END_REF][START_REF] Atangana | Domestication of Irvingia gabonensis: 1. Phenotypic variation in fruits and kernels in two populations from Cameroon[END_REF].

Similarly, geographic differentiation was also highlighted and used to develop vegetable culture (e.g. Angiosperms, Solanales, Solanaceae, Capsicum annuum; Ben Mansour-Gueddes

How to integrate geographic differentiation in domestication processes?

The success-stories presented demonstrate that considering geographic differentiation can unlock the potential contained in the wild biodiversity and pave the way to the domestication and production of new species populations. However, culture systems are very diverse, and domestication can occur in a culture system which can be quite different from wild

conditions. Yet, the variance of a phenotype is the result of both genetic and environmental factors [START_REF] Mackay | Introduction to quantitative genetics[END_REF][START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF]. Therefore, phenotypic differentiation observed in the wild between allopatric populations can result from (i) genetic

Take-home message

Domestication is here considered as the process in which a wild population is bred in a humancontrolled environment and this population evolves across generations from its wild ancestor, in ways making it more useful to humans who increasingly control their reproduction and food supply.

Beginning during the late Pleistocene, domestication is one of the most important developments in human history and deeply impacted human civilizations. Domestication attempts are still occurring nowadays, but failures are reported due to technical limitations, socio-economic limitations, or species-intrinsic features. Several traits were identified as limiting or facilitating domestication and subsequent production, showing that the ability to be successfully domesticated/produced varies between species. Approaches were developed to identify species of interest, but they do not consider an essential part of the wild biodiversity: the geographic differentiation. Geographic differentiation is well-known in the wild, including for traits identified as facilitation/limiting domestication and production. Some success-stories show how its consideration can lead to successful domestication/production. However, it is not possible to identify directly in the wild a priori favorable phenotypes. Therefore, there is a need to develop a standardized and pragmatic method in order up to integrate geographic differentiation in domestication processes.

might not be preserved in culture systems. Therefore, only genetically based differentiations are of interest for production which makes the detection of a priori favorable phenotypes directly in the wild unlikely.

The assessment of genetically based phenotypic differentiation in key traits between allopatric populations requires performing common-garden experiments. The common-garden experiment consists in applying the same environmental conditions to populations in order to study the genetic basis of traits without the confounding effects of the wild environment (de [START_REF] Villemereuil | Common garden experiments in the genomic era: new perspectives and opportunities[END_REF]. Indeed, this experimental set up allows to minimize potential effects of environmentally induced-phenotypic plasticity (West-Eberhard 2003). Yet, it is not pragmatic and ultimately feasible to sample and evaluate all populations across a species distribution range. Moreover, conspecific populations are not all divergent from each other, making such assessments uselessly time and money consuming. However, it is not optimal to test random populations or sampling populations over a small part of the distribution range of a particular species. Indeed, this strategy could lead to miss out the potential expressed by populations not sampled. Therefore, an efficient and pragmatic approach requires the development of a standardized method to integrate geographic differentiation in domestication processes. (i.e. low production per unit volume), minimal input of artificial substances in the system, low investment, low technological level, as well as a low human intervention. Aquaculture in ponds might be the best example to illustrate extensive systems. On the contrary, intensive production usually involves a much higher production per unit volume, higher costs, a strong human intervention, and a high control of rearing parameters. The recirculating aquaculture system (RAS) is an intensive system which is increasingly used nowadays in the aquaculture sector. A third system type exists which is an intermediate of the first two systems: the semiintensive system. This represents for instance a system in which the fry production is intensive, but the on-growing is performed in an extensive system (Lekang 2013).

INTRODUCTION INTRODUCTION

INTRODUCTION-

What is a recirculating aquaculture system?

A recirculating aquaculture system is an intensive fish production technology which aims at reusing the culture water through series of water treatment steps to depurate the water. This system is therefore a closed circuit and works using mechanical and biological filters. The system produces waste products (e.g. solid particles, ammonium) which are either removed or converted to non-toxic products. It is currently widely used in the aquaculture sector. Its advantages are a fully controlled environment, a low use of water, an efficient land and energy uses, disease control, and an ease to manipulate fish.

Ebeling and Timmons (2012); [START_REF] Espinal | Recirculating Aquaculture Technologies[END_REF] 2. Aquaculture: a fast-growing food production sector Nowadays, aquatic products represent a major part of the human diet (FAO 2018;

Pradeepkiran 2019). Until the 1950s, most of the human consumption of aquatic products was supplied by fisheries (FAO 2018). With the increasing human population and the associated rising demand for aquatic products (Figure 1A), fisheries output increased but wild stocks are limited. Fisheries production stagnating through time, there was a shift to target species further from coastlines and deeper in the ocean. However, nowadays, a large part of exploited wild fish stocks is considered as fully exploited or over-exploited [START_REF] Watson | Systematic distortions in world fisheries catch trends[END_REF][START_REF] Pauly | The Future for Fisheries[END_REF]FAO 2018). In addition, some fishery techniques are not considered as sustainable and are condemned by international organizations [START_REF] Myers | Environmental factors predict adaptive phenotypic differentiation within and between two wild Andean tomatoes[END_REF][START_REF] Pauly | The Future for Fisheries[END_REF][START_REF] Roberts | Deep impact: the rising toll of fishing in the deep sea[END_REF]. Fisheries are therefore no longer enough to keep supplying aquatic products to humanity. Shortly after the beginning of the stagnation in fisheries, aquaculture got developed in order to keep supplying the increasing demand in aquatic products (Figure 1B).

A B

Aquaculture is considered as the fastest-growing food production sector in the world and now provides more than 50 % of the aquatic products consumed worldwide [START_REF] Subasinghe | Global aquaculture and its role in sustainable development[END_REF]FAO 2018). The rapid growth of aquaculture presents several benefits, including the potential to (i) provide year-round incomes for farmers and fish supplies, (ii) reduce fishing pressure on wild stocks, and (iii) provide ecosystem services (e.g. bioremediation, wastewater treatment, enhancing depleted wild stocks; [START_REF] Klinger | Searching for solutions in aquaculture: charting a sustainable course aquaculture: the cultivation of algae and aquatic plants and animals[END_REF][START_REF] Troell | Does aquaculture add resilience to the global food system?[END_REF]. In this work, the focus was set on the production of fish species. The global average per capita supply of fish increased substantially these last fifty years and fish and shellfish account now for 6.5 % of total global protein consumption [START_REF] Troell | Does aquaculture add resilience to the global food system?[END_REF].

A will for sustainability: towards production diversification.

Aquaculture has become increasingly popular over the years [START_REF] Froehlich | Public perceptions of aquaculture : evaluating spatiotemporal patterns of sentiment around the world[END_REF]) but

remains criticized because of its potential unsustainable development and its negative environmental impacts [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF][START_REF] Martinez-Porchas | World aquaculture: environmental impacts and troubleshooting alternatives[END_REF][START_REF] Christou | Sustainable Food Production[END_REF][START_REF] Diana | Responsible Aquaculture in 2050: Valuing Local Conditions and Human Innovations Will Be Key to Success[END_REF]). These negative impacts include the destruction of habitats, the introduction of invasive species, a stress on freshwaters resources, an increased pressure on wild stocks when the life cycle is not fostered or in order to produce aquaculture feeds (i.e. fish meal and fish oil), enhanced disease/parasite transmission to wild populations, and pollution of ecosystems (Naylor et al. 2005;[START_REF] Silva Ss De | Alien Species in Aquaculture and Biodiversity: A Paradox in Food Production[END_REF][START_REF] Klinger | Searching for solutions in aquaculture: charting a sustainable course aquaculture: the cultivation of algae and aquatic plants and animals[END_REF][START_REF] Troell | Does aquaculture add resilience to the global food system?[END_REF]FAO 2018).

The low species diversity that contributes to production is one of the main issues hampering the sustainability of the aquaculture sector. Indeed, although numerous species are farmed (i.e. 212 in 2017; [START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF], a low number of species contribute significantly to the global production in terms of value and volume [START_REF] Teletchea | Domestication and genetics: what a comparison between land and aquatic species can bring?[END_REF]FAO 2018). In this way, 85% of the global fish aquaculture production relies on only 15 species [START_REF] Lazard | Les paradoxes et les questionnements soulevés par l'exploitation de la biodiversité (autochtone et introduite) en aquaculture[END_REF]. This is notably due to the fact that the production of many fish species (i) was abandoned after one or several trials due to zootechnical or economic issues or (ii) remains marginal when compared to the global volume of production [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]. The low species diversity contributing to production triggers numerous socio-economic and environmental issues (Box 4; [START_REF] Fauconneau | Diversification, domestication et qualité des produits aquacoles[END_REF][START_REF] Naylor | Aquaculture and ocean resoources: raising tigers of the sea[END_REF][START_REF] Asche | The salmon disease crisis in Chile[END_REF][START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF][START_REF] Silva Ss De | Alien Species in Aquaculture and Biodiversity: A Paradox in Food Production[END_REF]FAO 2018). First of all, low species diversity triggers a low resilience of aquaculture to face environmental changes or consumer demand/market fluctuations [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF][START_REF] Troell | Does aquaculture add resilience to the global food system?[END_REF]FAO 2018). This is particularly concerning given the predicted impact of climate change on aquaculture production [START_REF] Cochrane | Climate change implications for fisheries and aquaculture Overview of current scientific knowledge. Food and Agriculture Organization of the United Nations[END_REF]. Moreover, when the life cycle is not closed, it can generate fishing pressure on species which wild stocks are limited or collapsing [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF]. There is also a high risk of market collapse in the scenario of a disease outbreak as experienced by the salmon farming industry in Chile in 2005 due to an outbreak of infectious salmon anemia [START_REF] Godoy | First detection, isolation and molecular characterization of infectious salmon anaemia virus associated with clinical disease in farmed Atlantic salmon (Salmo salar) in Chile[END_REF][START_REF] Asche | The salmon disease crisis in Chile[END_REF]. Finally, a production model based on a few species neglects some parts of the market such as niche markets for which production is still inferior to the demand and where the development potential is high [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF] Nowadays, there is a will to develop a more sustainable aquaculture industry to ensure food security and cope with ongoing and future environmental changes. Several scenarios are currently prospected to promote the sustainability of the aquaculture sector. One potential way, promoted by the European commission and the FAO, relies on diversification. Several diversification strategies are advocated [START_REF] Harvey | Planning for aquaculture diversification: the importance of climate change and other drivers[END_REF]): (i) increasing the number of farmed species, (ii) increasing the evenness (i.e. contribution of each species to overall production) of farmed species, (iii) increasing the diversity within currently farmed species (i.e. strain diversity), and (iv) increasing the diversity of farming systems (e.g. integrated multitrophic aquaculture, aquaponics). Therefore, the production diversification is notably possible through new fish species domestication [START_REF] Muir | Managing to harvest? Perspectives on the potential of aquaculture[END_REF][START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF][START_REF] Subasinghe | Global aquaculture and its role in sustainable development[END_REF]Spanish Ministry of Environmental and Affairs 2010;FAO 2018;[START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF].

Particularities of teleost species domestication

Contrary to land species, domestication of fish species is significantly more recent and wild populations commonly co-exist with farmed populations [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Teletchea | Fish Domestication: An Overview[END_REF]). The time lag of 8 000 years between terrestrial agriculture and aquaculture can be partly explained by the fact that wild aquatic resources and fisheries used to be sufficient to supply the demand for fish products and because of technical challenges to rear aquatic species. However, a few species started to be considered for domestication a long time ago.

Evidences of fish culture trials date back about 3 500 years [START_REF] Nash | The History of Aquaculture[END_REF]. Traces of Nile tilapia (Actinopterygii, Cichliformes, Cichlidae, Oreochromis niloticus) and common carp (Actinopterygii, Cypriniformes, Cyprinidae, Cyprinus carpio) cultures have been reported, notably in South-east Asia [START_REF] Harache | Development and diversification issues in aquaculture. A historical and dynamic view of fish culture diversification[END_REF][START_REF] Balon | About the oldest domesticates among fishes[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] Nash | The History of Aquaculture[END_REF]; Table 4).

Although some other carp and salmonid species populations were also domesticated during the Middle Ages by monks in European monasteries, domestication processes only noticeably multiplied recently, notably since the 1960s [START_REF] Jobling | Farmed species and their characteristics[END_REF]). The will to diversify the production, facilitated by scientific and technological advances, has led to multiple domestication trials of new species [START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

Starting the domestication of a new fish species implies to select a candidate which (i) meets an unsatisfied human demand, need, or interest (e.g. Norway tried to diversify its production through halibut [Actinopterygii, Pleuronectiformes, Pleuronectidae, Hippoglossus sp.] and Atlantic cod [Actinopterygii, Gadiformes, Gadidae, Gadus morhua] production, but both species were out-competed by their wild fisheries; [START_REF] Harvey | Planning for aquaculture diversification: the importance of climate change and other drivers[END_REF], and (ii) has a potentially viable production, for instance though a potential occupation of different market segments than currently produced species (e.g. niche markets). Yet, domestication and subsequent production of new species populations are difficult process and can fail because of socio-economic criteria (e.g. over-estimation of future markets, under-estimation of costs, price elasticity) but also because of biological features (e.g. Table 4; [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] François | Considerations for the Selection and Commercialization of New or Alternate Species[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Harvey | Planning for aquaculture diversification: the importance of climate change and other drivers[END_REF]. It is hard to estimate the failure rate of aquaculture domestication/production attempts, but some insights can be given from species which were previously identified as candidates of interest.

For example, [START_REF] Abellán | Marine finfish species diversification: Current situation and prospects in mediterranean aquaculture[END_REF] suggested 25 Mediterranean marine fish with high potential for aquaculture but only eight were subsequently farmed [START_REF] Harvey | Planning for aquaculture diversification: the importance of climate change and other drivers[END_REF]). In the same way, among the top ten species identified by [START_REF] Lal | the Fiji Islands, Papua New Guinea, Vanuatu, Solomon Islands, Samoa & Tonga[END_REF] for inland aquaculture in the Pacific Islands, only two are currently farmed [START_REF] Harvey | Planning for aquaculture diversification: the importance of climate change and other drivers[END_REF].

However, the reasons explaining domestication failures, whether socio-economic or biological, remain often blurry. An additional insight can be seen in the large number of species populations which remain between the first and third levels of domestication due to major bottlenecks preventing the closure of the life cycle or production-related issues [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

As mentioned previously, there are some characteristics (biological and socio-economic) which can limit or facilitate domestication and subsequent production. Numerous of these characteristics apply to fish domestication (see examples in Table 4). This allowed developing methods to identify fish species of interest for aquaculture production diversification (e.g. [START_REF] Matthews | A simple and objective bioeconomic index for choosing species for culture -Aquatic Commons[END_REF][START_REF] Brummett | Species selection for smallholder aquaculture[END_REF][START_REF] Abellán | Marine finfish species diversification: Current situation and prospects in mediterranean aquaculture[END_REF][START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF][START_REF] Suquet | A systematic market approach to species diversification : a French case study[END_REF][START_REF] Lal | the Fiji Islands, Papua New Guinea, Vanuatu, Solomon Islands, Samoa & Tonga[END_REF][START_REF] Alvarez-Lajonchère | Aquaculture species selection method applied to marine fish in the Caribbean[END_REF]

Favoring characteristics Examples of wild geographic differentiation

Large gregarious groups [START_REF] Magurran | Variation in schooling and aggression amongst guppy (Poecilia Reticulata) populations in Trinidad[END_REF]; [START_REF] Wark | Heritable differences in schooling behavior among threespine stickleback populations revealed by a novel assay[END_REF] Tolerance to conspecifics / Lack of aggressiveness [START_REF] Huntingford | Do inter-and intraspecific aggression vary in relation to predation pressure in sticklebacks?[END_REF]; [START_REF] Herczeg | Predation mediated population divergence in complex behavior of nine-spined stickleback (Pungitius pungitius)[END_REF]

Geographic differentiation in aquaculture standardized conditions

Wild fish allopatric populations experience diverse selective pressures and spatio-temporal changes in biotic and/or abiotic parameters. One could expect to see adaptations to local conditions in these populations [START_REF] Mayr | Animal species and evolution[END_REF]). These local adaptations could have triggered changes in key traits for aquaculture. A geographic differentiation was shown in the wild for a wide range of traits, such as age at sexual maturity or fecundity [START_REF] Houde | Comparative growth, mortality, and energetics of marine fish larvae: temperature and implied latitudinal effects[END_REF][START_REF] Conover | Seasonality and the scheduling of life-history at different latitudes[END_REF][START_REF] Fleming | Reproductive strategies of Atlantic salmon: ecology and evolution[END_REF][START_REF] Blanck | Large-scale intraspecific variation in life-history traits of European freshwater fish[END_REF], including several domestication/productionfavoring characteristics (see examples in Table 4). Yet, as mentioned previously, only wild genetically based differences are of interest for aquaculture. Several studies highlighted the loss of inter-populational trait divergences in a common-garden environment due to the fact that environmental factors (i.e. phenotypic plasticity; [START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF][START_REF] Kelly | Phenotypic plasticity: molecular mechanisms and adaptive significance[END_REF] outweighed any genetic contributions: e.g. for Cyprinus carpio (Vandeputte et al. 2002),

Gadus morhua [START_REF] Godø | Growth and maturation of Norwegian coastal cod and Northeast Arctic cod under different conditions[END_REF], or Perca flavescens (Actinopterygii, Perciformes, Percidae ; Rosburg 2017). Therefore, the detection of a priori favoring phenotypes in the wild remains unreliable without comparison of performances in a standardized environment corresponding to the culture system.

In order to evaluate the knowledge acquired on geographic differentiation in teleost species (i.e. when comparing allopatric populations in a standardized environment), studies investigating geographic differentiation in a common-garden environment were reviewed (ongoing review during the course of this work using Google scholar, ScienceDirect, and PubMed). The various terms used at the intraspecific level made this synthesis difficult and several key words were used, such as "geographic origin", "strain", "population", "latitude", "common-garden", "intraspecific, "population origin", "stock", "race", "form", and "variety".

Only studies highlighting inter-populational differences in a common-garden experiment are presented here (n=177; Annex 1, Figure 2). 60 % of these studies compared populations during the first generations (F0, which corresponds to wild individuals placed in a controlled

Development

It should be noted that a large part of these studies focused on Salmonidae (Actinopterygii, Salmoniformes; 39 %; Figure 2a), followed by Gadidae (Actinopterygii, Gadiformes; 10 %).

This could be expected given the major importance of Salmonidae in worldwide aquaculture (FAO 2018) and the consideration of intraspecific variability in the salmon domestication programs (see further). Looking closer at which biological functions were investigated, 39 % of these studies investigated growth and product quality traits (Figure 2b; among which 28 % focused exclusively on growth traits and 24 % on growth and other transversal traits [mostly survival rate]). This is not surprising since growth is the premium criterion considered for domestication processes (e.g. [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF][START_REF] Rye | Genetic improvement programs for aquaculture species in developed countries[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. Indeed, domestication processes, including selective breeding programs, often focused, at least in the first steps, on growth characteristics since growth is considered as the most important socioeconomic criterion [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF]Gjedrem 2005a). However, geographic differentiation was also highlighted for all other biological functions/other traits (Figure 2b) and for a diverse range of traits of interest for aquaculture (Table 5). Even though geographic differentiation was shown for a wide range of taxa and for many key traits for domestication and aquaculture production ( and performances were evaluated in several marine farms [START_REF] Gjedrem | Genetic origin of Norwegian farmed Atlantic salmon[END_REF][START_REF] Gjedrem | The first family-based breeding program in aquaculture[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. Several traits were studied and allowed to highlight a differentiation between allopatric populations for several commercially important traits (Table 6), even though the global between-population variation was low (< 10 %) compared to the within-population variability [START_REF] Gjedrem | Genetic origin of Norwegian farmed Atlantic salmon[END_REF][START_REF] Gjøen | Past, present, and future of genetic improvement in salmon aquaculture[END_REF]. This research program led to a fruitful development of the Atlantic salmon industry [START_REF] Gjøen | Past, present, and future of genetic improvement in salmon aquaculture[END_REF][START_REF] Gjedrem | The first family-based breeding program in aquaculture[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. In the 1990's, a selective breeding program also started for Nile tilapia (Oreochromis niloticus). It aimed at evaluating performances of four farmed populations (originating from different geographic locations) and four African wild populations.

Differences were highlighted between populations for survival and growth [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF]. The use of a base population, constituted by broodstock selected from all purebred (i.e.

crosses between individuals from the same population) and crossbred (i.e. crosses between several populations) groups, allowed to greatly develop Nile tilapia production leading to a worldwide impact on aquaculture [START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. Other examples at smaller scales can be found in literature, such as Guinean tilapia (Actinopterygii, Perciformes, Cichlidae, Coptodon guineensis) production in Ghana [START_REF] Agyakwah | Genetic characterization and early life culture performance evaluation of four ghanaian populations of Tilapia guineensis (Pisces: Cichlidae)[END_REF][START_REF] Falk | Genetic diversity of west African lagoon tilapias and its implications for fisheries, aquaculture and biodiversity conservation: case studies on Sarotherodon melanotheron, Sarotherodon nigripinnis and Tilapia guineensis[END_REF]) and European seabass (Actinopterygii, Perciformes, Moronidae, Dicentrarchus labrax) production in Israel [START_REF] Gorshkov | Culture performance of different strains and crosses of the European sea bass (Dicentrarchus labrax) reared under controlled conditions at Eilat, Israel[END_REF]. These examples refer to species for which the life cycle was closed and production well established (i.e. advanced stages of domestication, at least for several populations). Yet, the consideration of geographic differentiation could be useful to facilitate domestication of new candidate species. It could also be useful for species at incipient domestication levels which present major bottlenecks impeding domestication (e.g. low fertility, low survival rate), such as species populations remaining in the first levels of domestication according to [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

Article

Trait(s) [START_REF] Gjedrem | Selection experiments with salmon. I. Differences in resistance to vibrio disease of salmon parr (Salmo salar)[END_REF] Resistance to vibrio disease of salmon parr [START_REF] Kanis | A genetic analysis of egg, alevin and fry mortality in salmon (Salmo salar), sea trout (Salmo trutta) and rainbow trout (Salmo gairdneri)[END_REF] Mortality for eggs and fingerlings [START_REF] Terje | Selection experiments with salmon. II. Proportion of Atlantic salmon smoltifying at 1 year of age[END_REF] Percentage of salmon smoltifying at one year old [START_REF] Refstie | Selection experiments with salmon: III. Genetic and environmental sources of variation in length and weight of Atlantic salmon in the freshwater phase[END_REF] Body weight after 190 days [START_REF] Gunnes | Selection experiments with salmon IV Growth of Atlantic Salmon during two years in the sea[END_REF] Body growth (weight and length) after two years at sea [START_REF] Gjerde | Complete diallel cross between five strains of Atlantic salmon[END_REF] Egg diameter, body weight, survival, percentage of fish expected to spawn by the following spawning season [START_REF] Gjerde | Estimates of phenotypic and genetic parameters for carcass traits in Atlantic salmon and rainbow trout[END_REF] Ungutted and gutted body weight, body length, dressing percentage, meatiness, flesh color, liver color, and percentage of fish expected to spawn by the following spawning season

The consideration of geographic differentiation could not solely be useful to facilitate domestication of new candidate species in the current diversification context. Indeed, in addition of enhancing diversity within animal production systems to increase resilience to climatic or economic hazards, there are several other challenges to promote sustainable production systems such as (i) improving animal welfare ("state of the individual as it copes with the environment"; [START_REF] Ashley | Fish welfare: Current issues in aquaculture[END_REF][START_REF] Browman | Welfare of aquatic animals: where things are, where they are going, and what it means for research, aquaculture, recreational angling, and commercial fishing[END_REF]Saraiva et al. 2019), (ii) developing alternative aquaculture systems (e.g. integrated multi-trophic aquaculture

["cultivation of aquaculture species with other extractive aquaculture"]; [START_REF] Dumont | Prospects from agroecology and industrial ecology for animal production in the 21st century[END_REF][START_REF] Dumont | Forty research issues for the redesign of animal production systems in the 21st century[END_REF][START_REF] Thomas | Agro-écologie et écologie industrielle : deux alternatives complémentaires pour les systèmes d'élevage de demain[END_REF]), (iii) producing robust animals (i.e. animals able to "survive, reproduce, and maintain production in a wide variety of environmental conditions"; [START_REF] Knap | Breeding robust pigs[END_REF][START_REF] Dumont | Forty research issues for the redesign of animal production systems in the 21st century[END_REF], and (iv) decreasing the reliance on fish meal and fish oil in aquafeeds as these ingredients come from capture fisheries through the development of a plant-based diet aquaculture [START_REF] Naylor | Feeding aquaculture in an era of finite resources[END_REF][START_REF] Rey-Valette | Quelques pistes sur l'avenir de l'aquaculture française en 2040[END_REF]. All these challenges aiming at developing a more sustainable aquaculture imply that new domestication programs might need to be developed. This is true for new candidate species but also for currently produced species. Indeed, current farmed stocks might not be adequate for new purposes such as developing production in new aquaculture systems or finding phenotypes which are interesting for polyculture or plant-based diet. In addition, given the diversity of environments and aquaculture systems, it is highly plausible that one biological unit will not be suitable for all purposes. The best population for a particular aquaculture system might not be the best for another system. Therefore, the consideration of geographic differentiation could be helpful to (i) facilitate domestication of new candidate species or species at the beginning of the domestication process which face major bottlenecks/production issues and (ii) answer to current and future challenges.

How to integrate geographic differentiation in fish domestication and production processes

The success-story examples highlight the potential usefulness of considering geographic differentiation in aquaculture domestication processes. However, there is no standardized methodology available to consider geographic differentiation when starting domestication and production of new fish species. Indeed, looking back at the Atlantic salmon success-story, the sampling design focused on a small part of the native distribution range (which might explain the low between-population variance). Applying such a strategy could lead to miss out the potential contained in non-sampled populations. Yet, once again, it is not feasible to consider all populations across the distribution range. This underlines the importance of developing a pragmatic and standardized approach to domesticate new candidates while considering geographic differentiation.

In addition, as mentioned previously, domestication trials, as well as selective breeding programs, often focus in the first steps on growth rate. Yet, a successful domestication and production requires the favorable expression of traits involved in several biological functions: a population can be domesticated if it can reproduce (reproductive and behavior functions), grow (growth, behavior, and development functions), feed (nutrition and behavior functions), and overcome stresses (e.g. resistance to diseases, immune, and behavior functions).

Therefore, a multi-function and multi-trait approach is required to evaluate the aquaculture potential at the intraspecific level. A careful assessment needs to be led regarding which traits should be considered in the aquaculture potential assessment.

Take-home message

Aquaculture is the fastest-growing food production sector in the world and domestication of aquatic species is quite recent. Nowadays, there is a will to diversify the production, notably through new species domestication. However, domestication and subsequent production of a new population is difficult and can fail. New species domestication trials could be facilitated by considering geographic differentiation. Even though geographic differentiation has been poorly considered at the beginning of the domestication process, a few success stories at more advanced domestication stages highlight its usefulness. Moreover, a geographic differentiation has been shown in literature for a wide range of species and for diverse key traits in standardized conditions (i.e. domestication system).

Assuming differentiation in performances are, at least partly, genetically coded, it could allow beginning new domestication trials with the best unit available in the wild. However, a methodology to consider geographic differentiation in new domestication processes needs to be developed.

Considering that domestication of fish species is quite recent and the will to diversify production, there is an opportunity to standardize new domestication processes. This work hereby promotes that the potential contained in the wild should be assessed to facilitate domestication and subsequent production of new species. The domestication process could begin using the wild intraspecific unit(s) presenting the highest aquaculture potential in standardized conditions. Assuming that key traits are at least partially genetically coded, this would allow starting new domestication processes with the best biological unit(s) available in the wild and increase chances of domestication success.

OBJECTIVES AND HYPOTHESES

significant units; [START_REF] Frankham | Resolving taxonomic uncertainties and defining management units[END_REF][START_REF] Haig | Taxonomic Considerations in Listing Subspecies Under the U.S. Endangered Species Act[END_REF]) could be a solution but these classifications (i) were not available for European perch and (ii) have been criticized because the choice of definition criteria is debated [START_REF] Ryman | Protection of intraspecific biodiversity of exploited fishes[END_REF][START_REF] Fraser | Adaptive evolutionary conservation: towards a unified concept for defining conservation units[END_REF][START_REF] Phillimore | Are subspecies useful in evolutionary and conservation biology?[END_REF][START_REF] Braby | The subspecies concept in butterflies: has its application in taxonomy and conservation biology outlived its usefulness?[END_REF]. Therefore, a classification needed to be established for P. fluviatilis. We needed to select a proxy which could (i) highlight prospective units which likely display different abilities to be domesticated and fruitfully produced and (ii) be easily assessed at large scale. As a first approach, we chose to perform a phylogeographic classification. Indeed, population groups having different/independent demographic histories and/or potential local adaptations are likely to present divergences in key traits. Therefore, we used genetic differentiation in neutral markers (i.e. theoretically not submitted to selection and not influencing fitness) as a proxy to highlight population groups with potential divergences in key traits (as previously suggested in [START_REF] Pouyaud | Physiological basis of latitudinal growth differences in Menidia menidia: variation in consumption or efficiency?[END_REF].

Once intraspecific classification is established, the different PUs must be evaluated in the same environment (i.e. common garden experiment) with rearing conditions being as close as possible to the domestication system used for production. The chapter 4 illustrates the second and third steps of the integrative approach (aim A2). This chapter is aimed at (i) evaluating differentiation in performances of populations representative of the different prospective units in standardized conditions (aim A1, validation of H1), (ii) demonstrating the usefulness of the multi-function and multi-trait approach since growth is not the only important trait for production, and (iii) elaborating an aquaculture potential index to take into account the variable importance levels of traits studied according to the opinion of stakeholders. This index allows making a consensus between all trait results to facilitate the identification of units with high potential for aquaculture (verification of H2).

Finally, the relevance of the genetic classification assessed in the third chapter can be questioned. In chapter 5, we assessed the relevance of three alternative proxies (i.e. genetic, habitat, and hydrologic/geographic proxies) to highlight inter-populational divergences in key traits for larviculture in P. fluviatilis. This chapter corresponds to a retro-evaluation of the relevance of the proxy used in the third chapter.

SPECIES USED AS A TEST CASE

European perch distribution

The European perch (Figure 3) is a temperate species which is widespread across Eurasia (Figure 4) due its strong tolerance to temperature and salinity variations [START_REF] Kottelat | Handbook of European Freshwater Fishes[END_REF]).

It can be found from the United Kingdom to Siberia in a diverse range of habitats such as rivers, lakes, estuaries, or ponds, from eutrophic to oligotrophic waters [START_REF] Collette | Systematics and zoogeography of the fishes of the family Percidae[END_REF][START_REF] Stepien | Taxonomy, Distribution, and Evolution of the Percidae[END_REF]. This species was also introduced across Eurasia, for instance in Italy, Spain, and, Ireland, but also in other continents such as Australia and Africa [START_REF] Kottelat | Handbook of European Freshwater Fishes[END_REF]Kestemont et al. 2015a).

Biology of wild European perch

European perch feeding regime varies through ontogeny depending on size and foraging habitat: from zooplanktivory when larvae occupy the water column in the pelagic zone, to benthivory (mostly macroinvertebrates) in the littoral zone and later piscivory in both pelagic and littoral zones [START_REF] Feiner | Environmental Biology of Percid Fishes[END_REF][START_REF] Magnhagen | Behavior of percid fishes in the wild and its relevance for culture[END_REF]. Individuals are overall opportunistic [START_REF] Feiner | Environmental Biology of Percid Fishes[END_REF]. European perch is considered as a social fish, but interindividual interactions also depend on ontogeny (among other related factors such as predation pressure; [START_REF] Vainikka | Predation risk allocation or direct vigilance response in the predator interaction between perch (Perca fluviatilis L.) and pike (Esox lucius L.)?[END_REF][START_REF] Magnhagen | Behavior of percid fishes in the wild and its relevance for culture[END_REF]. Indeed, in general, larvae are found in large shoals, the number of individuals in the shoal tends to decrease with size, and some adults can even be solitary [START_REF] Magnhagen | Behavior of percid fishes in the wild and its relevance for culture[END_REF].

The European perch is an early spring spawner without parental care [START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF].

A homing behavior was described [START_REF] Järv | Migrations of the perch (Perca fluviatilis L.) in the coastal waters of western Estonia[END_REF] even though the dispersion distance of European perch remains under investigation. Sexual maturation for reproduction requires low temperatures and is overall more precocious in males (late 1 st year-2 nd year) than females (late 2 nd year to 4 th year; [START_REF] Kottelat | Handbook of European Freshwater Fishes[END_REF][START_REF] Abdulfatah | Effects of photothermal kinetics and amplitude of photoperiod decrease on the induction of the reproduction cycle in female Eurasian perch Perca fluviatilis[END_REF]. When females are mature, the spawning is triggered by a set of endogenous and exogenous mechanisms, notably through temperature and photoperiod changes [START_REF] Abdulfatah | Etude du déterminisme environnemental du cycle de reproduction chez la perche commune (Perca fluviatilis )[END_REF][START_REF] Feiner | Environmental Biology of Percid Fishes[END_REF]. The spawning occurs once a year, between February and June given the strong latitudinal variation [START_REF] Kottelat | Handbook of European Freshwater Fishes[END_REF]; Table 7), with southern populations spawning generally earlier than northern populations [START_REF] Feiner | Environmental Biology of Percid Fishes[END_REF]. Eggs are grouped in clusters -commonly named egg ribbons-which are found lying over submerged substrates (Figure 5). Each mature female spawns all its eggs in a single egg ribbon and eggs are fertilized externally by one or, more frequently, several males [START_REF] Bruslé | Biologie des poissons d'eau douce européens[END_REF][START_REF] Kottelat | Handbook of European Freshwater Fishes[END_REF][START_REF] Couture | Introduction to biology of Perch[END_REF]. A relationship was suggested between the ribbon size and the female size [START_REF] Craig | Population dynamics of perch, Perca fluviatilis L. in Slapton Ley, Devon[END_REF][START_REF] Dubois | Correlation between the size of mature female perch (Perca fluviatilis L.) and the width of their egg strands in Lake Geneva[END_REF][START_REF] Schaerlinger | Evaluation and improvements of egg and larval quality in percid fishes[END_REF], but this is not verified everywhere [START_REF] -Dalimier | Etude éco-éthologique de la reproduction de la perche (Perca fluviatilis L.): observations en plongée dans une carrière inondée[END_REF].

Table 7: Examples of variation of the spawning period and temperature at spawning between allopatric populations of European perch. Adapted from [START_REF] Fontaine | Broodstock Management and Control of the Reproductive Cycle[END_REF]. NR: Not Reported. FAO 2018). Production diversification could be facilitated by the consideration of some microterritories which display a strong link between the territory history/traditions, a specific landscape (e.g. pond, lake), and human populations [START_REF] Fontaine | L'élevage de la perche commune, une voie de diversification pour l'aquaculture continentale[END_REF][START_REF] Fontaine | Domestication of the Eurasian Perch (Perca fluviatilis)[END_REF]. Indeed, cultural traditions can be seen, associated with a consumption of specific products (e.g. smoked eel in the Netherlands, fried cyprinids in Luxembourg), which allows to foresee production development in these specific regions. European perch is one of these niche products presenting a demand in Alpine areas (Switzerland, Italy, and France), Benelux, and Scandinavia. The European perch presents a strong socio-economic interest for fisheries, recreational fishing, and aquaculture [START_REF] Stepien | Taxonomy, Distribution, and Evolution of the Percidae[END_REF]Policar et al. 2019).

Domestication and bottlenecks

The European perch domestication process started in the 1990s and has been suggested as one of the most interesting species for European inland aquaculture development while considering other economic sectors already running (i.e. no competition involved). Given the A B C D variability of quality of individuals from fisheries and the will to have products available all year round, perch aquaculture production was promoted as the path to follow [START_REF] Fontaine | L'élevage de la perche commune, une voie de diversification pour l'aquaculture continentale[END_REF][START_REF] Watson | The European market for perch (Perca fluviatilis)[END_REF]). After production trials in ponds, cages, and RAS, the latter was highlighted as the best production system for this species, for instance due to nanism issues in ponds and sensibility to water quality variations and diseases (Fontaine and Teletchea 2019 and references therein). Most of the production nowadays is performed in RAS even though other culture systems are explored such as mesocosm methods to produce juveniles (e.g. perch production in Ireland; Kestemont et al. 2015b;Policar et al. 2019). To date, between 500 and 1 000 tons of perch are produced per year in RAS [START_REF] Fontaine | Domestication of the Eurasian Perch (Perca fluviatilis)[END_REF], including 100 tons in France, and production remains inferior to the demand. Regarding the consumption market, this fish is consumed at different sizes and in various forms (e.g. wholefish, fillet; Fontaine 2004). However, despite all the research efforts to improve perch production (e.g. reproduction [START_REF] Abdulfatah | Etude du déterminisme environnemental du cycle de reproduction chez la perche commune (Perca fluviatilis )[END_REF][START_REF] Castets | Fonction de reproduction et régulation de la qualité chez la perche commune Perca fluviatilis[END_REF], larval rearing [START_REF] Mélard | Relationships between stocking density, growth, cannibalism and survival rate in intensively cultured larvae and juveniles of Perch (Perca fluviatilis)[END_REF][START_REF] Kestemont | Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: Biotic and abiotic influences[END_REF]], feeding and growth [START_REF] Fiogbé | Optimum daily ration for Eurasian perch Perca fluviatilis L. reared at its optimum growing temperature[END_REF][START_REF] Fontaine | Influence of feeding level on growth, intraspecific weight variability and sexual growth dimorphism of Eurasian perch Perca fluviatilis L. reared in a recirculation system[END_REF][START_REF] Fiogbé | Optimum daily ration for Eurasian perch Perca fluviatilis L. reared at its optimum growing temperature[END_REF]), there are still many bottlenecks limiting its production and upscaling (Figure 6; [START_REF] Fontaine | L'élevage de la perche commune, une voie de diversification pour l'aquaculture continentale[END_REF]Kestemont et al. 2015a;[START_REF] Fontaine | Domestication of the Eurasian Perch (Perca fluviatilis)[END_REF]Policar et al. 2019). Therefore, there is a need to improve the domestication and production of this species.

The European perch production cycle

There are several stages in P. fluviatilis production:

 Reproductive phase: During the breeding period, the reproductive cycle is divided in three steps: primary growth (from the beginning of gametogenesis up to the cortical alveoli stage), secondary growth (early and late vitellogenesis), and final oocyte maturation. Egg ribbons are then stripped manually, and external fertilization is performed by collecting sperm from males [START_REF] Fontaine | Broodstock Management and Control of the Reproductive Cycle[END_REF][START_REF] Żarski | Controlled reproduction of wild Eurasian perch. A hatchery manual[END_REF].

 Hatchery-Nursery: The embryonic period lasts between fertilization and first oral feeding.

It ) corresponds to the embryonic-to-larval transition [START_REF] Alix | An alternative developmental table to describe nonmodel fish species embryogenesis: application to the description of the Eurasian perch (Perca fluviatilis L. 1758) development[END_REF]. The larval period starts with exogenous feeding. During that period, larvae inflate their swim bladder by going to the surface and gulping air, cannibalism behavior onsets from 11 days post-hatching, and individuals switch from live prey feeding to inert diet during the weaning period [START_REF] Bandelt | Median-joining networks for inferring intraspecific phylogenies[END_REF]Kestemont et al. 2015b;[START_REF] Kupren | Early development and allometric growth in hatchery-reared Eurasian perch, Perca fluviatilis L[END_REF]. The transition between larvae and juveniles is not clear, usually juveniles are considered as such once they attain the same morphology as adults (i.e. end of metamorphosis; [START_REF] Urho | Characters of larvae-what are they?[END_REF][START_REF] Schaerlinger | Evaluation and improvements of egg and larval quality in percid fishes[END_REF][START_REF] Kupren | Early development and allometric growth in hatchery-reared Eurasian perch, Perca fluviatilis L[END_REF].

 On-growing phase: All anatomic structures are developed. This phase consists of growing fish until market size. The difference between a juvenile and an adult usually just relies on the ability to start a reproductive cycle (i.e. sexual maturity). At the end of this phase, individuals are harvested for the market or kept as broodstock.

In this PhD work, it was not possible to work on the whole life cycle since it takes about 2.5 years to perform a full cycle (egg to egg). Therefore, the focus was set on fist life stages, more particularly larval stages from one to 60 days post-hatching, since: (i) the experimental length was appropriate for the PhD project, (ii) many bottlenecks are tied to this life stage (e.g. mortalities due to cannibalism, high deformity rate, low survival rate), and (iii) it is easier to collect and acclimatize wild egg ribbons than to catch and transport juveniles or adults to the culture system.

5. Perca fluviatilis and the three-step integrative approach

Geographic differentiation

A geographic differentiation in European perch was already highlighted in the wild between allopatric populations, for instance regarding color [START_REF] Pimakhin | Color variability of Eurasian perch (Perca fluviatilis): a review[END_REF], growth rate, size at maturity [START_REF] Rask | Differences in growth of perch (Perca fluviatilis L.) in two small forest lakes[END_REF][START_REF] Heibo | Life-history variation in perch (Perca fluviatilis L.) in five neighbouring Norwegian lakes[END_REF]Heibo et al. 2005;Heibo and Magnhagen 2005), filet quality [START_REF] Mairesse | Effects of geographic source, rearing system, and season on the nutritional quality of wild and farmed Perca fluviatilis[END_REF]), activity patterns (Jacobsen et al. 2015), and boldness (Magnhagen 2006;[START_REF] Magnhagen | Risk-taking behavior in foraging perch: does predation pressure influence age-specific boldness?[END_REF][START_REF] Hellström | The influence of experience on risk taking: results from a common-garden experiment on populations of Eurasian perch[END_REF]. Geographic differentiation has also been highlighted for several key traits in aquaculture conditions, including traits which were shown as limiting/facilitating factors for domestication and subsequent production (Table 8). However, these studies were performed on a limited number of traits, mostly related to growth and survival. Therefore, geographic differentiation in aquaculture conditions remains to be assessed for traits linked to other biological functions. The current distribution of species is the result of past and current events [START_REF] Taberlet | Biodiversity at the intraspecific level: The comparative phylogeographic approach[END_REF][START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF][START_REF] Avise | Phylogeography: retrospect and prospect[END_REF]Hewitt 2004a,b). Therefore, the current geographic differentiation patterns must be studied considering historical forces (e.g. bottlenecks, migrations, vicariance). Phylogeography consists of studying the distribution of lineages through genetic inter-individual variations and has been particularly investigated for European species [START_REF] Avise | Intraspecific phylogeography: the mitochondrial DNA bridge between population genetics and systematics[END_REF][START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]Hewitt 2004b). It relies on the use of neutral genes since they are not submitted to selection and depend on the demographic history of the population they belong to (Note: excluding random phenomena such as genetic drift and mutation). It is useful to study the recent history of populations, particularly since the last glaciations. Indeed, climatic shifts during the Quaternary led to cycles of contraction and expansion of species ranges which shaped the current genetic diversity and differentiation patterns [START_REF] Andersen | The ice age world: An introduction to quaternary history and research with emphasis on North america and northern europe during the last 2.5 million[END_REF][START_REF] Hewitt | The genetic legacy of the Quaternary ice ages[END_REF]Hewitt , 2004a)). During glaciations, some populations survived in more favorable areas called refugia, in which genetic differentiations accumulated across time. When ice retreated, they could recolonize empty niches, often implicating a loss of genetic diversity because of multiple founder events [START_REF] Hewitt | Some genetic consequences of ice ages, and their role in divergence and speciation[END_REF][START_REF] Hewitt | Post-glacial re-colonization of European biota[END_REF][START_REF] Stewart | Refugia revisited: individualistic responses of species in space and time[END_REF].

Once established in a territory, new migrants might have had to compete with local populations, which likely favored the persistence of genetic specificities inherited from post-glacial recolonizations [START_REF] Hewitt | Post-glacial re-colonization of European biota[END_REF]. The existence of several refugia often promoted the emergence of genetically differentiated lineages [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]Hewitt 2004b). On the contrary, populations originating from recent divergence events are characterized by a lesser important differentiation degree in neutral markers.

Overall, the phylogeographic approach allows highlighting genetically differentiated groups of populations which present different demographic histories. These groups are likely to present divergences in key traits due to local adaptation or random processes (e.g. genetic drift).

Box 5: How to perform a phylogeographic study? (1/2) Several steps are needed to perform a phylogeographic study:

(A) Sampling across the distribution range in order to consider the different lineages potentially originating from different refugia. The sampling size relies on a compromise between the extent of distribution, the markers' polymorphism degree, and the budget.

(B) Choice of genetic markers: Mitochondrial markers are usually used in phylogeographic studies due to [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF][START_REF] Zhang | Nuclear DNA analyses in genetic studies of populations : practice , problems and prospects[END_REF][START_REF] Makhrov | Dispersal routes and species identification of freshwater animals in Northern Europe: a review of molecular evidence[END_REF][START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF][START_REF] Bowen | Phylogeography unplugged: comparative surveys in the genomic era[END_REF]) : (i) their high mutation rate and their lower effective population size (one-quarter that of nuclear genes) which maximize chances to detect differentiation without an extensive sampling effort, (ii) their low rate of recombination (i.e. genetic material exchange between different organisms) which leads to the assumption that all sites have the same genealogical history, (iii) their high prevalence in cells which makes them easier to amplify, and (iv) their haplotypic status which facilitates their sequencing (but see rare cases of heteroplasmy [i.e. presence of more than one type of organellar genome within a cell/individual], including for Perca fluviatilis; Nesbø et al. 1998a). In this work, we chose to use four mitochondrial markers which are widely used in freshwater teleost studies: cytochrome b (e.g. [START_REF] Houdt | Phylogenetic relationships among Palearctic and Nearctic burbot (Lota lota): Pleistocene extinctions and recolonization[END_REF][START_REF] Culling | European colonization by the spined loach (Cobitis taenia) from Ponto-Caspian refugia based on mitochondrial DNA variation[END_REF], D-loop (e.g. [START_REF] Weiss | Complex patterns of colonization and refugia revealed for European grayling Thymallus thymallus, based on complete sequencing of the mitochondrial DNA control region[END_REF], 16S rRNA (e.g. [START_REF] Costedoat | Heterogeneous colonization pattern of European Cyprinids, as highlighted by the dace complex (Teleostei: Cyprinidae)[END_REF], and cytochrome oxidase I (e.g. [START_REF] Nwani | DNA barcoding discriminates freshwater fishes from southeastern Nigeria and provides river system-level phylogeographic resolution within some species[END_REF]. However, mitochondrial markers present some disadvantages because (i) they are maternally inherited and therefore biased to female-mediated processes (e.g. not reflecting potential differential dispersions between males and females; [START_REF] Prugnolle | Inferring sex-biased dispersal from population genetic tools: a review[END_REF][START_REF] Toews | The biogeography of mitochondrial and nuclear discordance in animals[END_REF] and (ii) nuclear introgressions can trigger technical issues [START_REF] Bruford | DNA markers reveal the complexity of livestock domestication[END_REF][START_REF] Ballard | The population biology of mitochondrial DNA and its phylogenetic implications[END_REF][START_REF] Larson | A population genetics view of animal domestication[END_REF]. Because of these limitations, the use of mitochondrial markers should be coupled with nuclear markers [START_REF] Nichols | Gene trees and species trees are not the same[END_REF][START_REF] Ballard | The incomplete natural history of mitochondria[END_REF][START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF]. However, the study of nuclear markers is more complicated given their low mutation rate and because it requires cloning before sequencing to separate alleles from heterozygous individuals. Yet, the use of microsatellite markers (i.e. repetitive nucleotidic motifs of one to six base pairs)

provides an interesting alternative coupled with mitochondrial markers (Beheregaray 2008). Microsatellites have been widely used in teleost genetic studies [START_REF] Makhrov | Dispersal routes and species identification of freshwater animals in Northern Europe: a review of molecular evidence[END_REF]. They are supposedly neutral, biparentally inherited, highly polymorph, spread across the genome, and very useful to characterize genetic diversity [START_REF] Zhang | Nuclear DNA analyses in genetic studies of populations : practice , problems and prospects[END_REF][START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF].

Box 5: How to perform a phylogeographic study ? (2/2) However, microsatellites also present some disadvantages such as homoplasy (i.e.

similarities in fragment length which are not inherited from a common ancestor but linked to changes in adjacent areas such as flanking regions), high development costs, or mutation rate which varies considerably between organisms [START_REF] Zhang | Nuclear DNA analyses in genetic studies of populations : practice , problems and prospects[END_REF][START_REF] Miah | A review of microsatellite markers and their applications in rice breeding programs to improve blast disease resistance[END_REF][START_REF] Abdurakhmonov | Introduction to Microsatellites: Basics, Trends and Highlights[END_REF]. The combination of these two markers could therefore help to elucidate more accurately the phylogeographic structure.

(C) Acquisition of data: Obtaining sequences (or scores for microsatellites) requires DNA extraction, amplification of sequences through polymerase reaction chain with chosen primers, and Sanger sequencing (or genotyping in the case of microsatellites).

(D) Data analysis:

-Polymorphism: The analysis of polymorphism relies on the calculation of haplotypic or allelic diversity (i.e. variant forms of a gene).

-Phylogeographic structure: When there is a polymorphism, it is possible to evaluate the distribution of genetic variance between populations through an Analysis of MOlecular VAriance (AMOVA), which gives the percentage of variance existing between population groups, within population groups, and within populations [START_REF] Excoffier | Analysis of molecular variance inferred from metric distances among DNA haplotypes: Application to human mitochondrial DNA restriction data[END_REF]). The AMOVA takes into account haplotype sequences and nucleotidic distances between haplotypes. It allows to calculate a F ST value (which varies between 0 [no genetic differentiation] and 1 [no gene flow, strong genetic structure]) and a nonparametric permutation test allows to calculate the significativity (p-value) associated to each structure level. However, this analysis requires defining groups according to a chosen a priori. The Spatial Analysis of MOlecular Variance (SAMOVA) is based on the AMOVA but allows to define groups of populations which are geographically homogenous and genetically differentiated [START_REF] Dupanloup | A simulated annealing approach to define the genetic structure of populations[END_REF]. This procedure maximizes genetic differentiation between groups and minimizes differentiation within groups. Regarding microsatellite analyses, several approaches can be used but the most common method is the Bayesian clustering method implemented in STRUCTURE [START_REF] Pritchard | Inference of population structure using multilocus genotype data[END_REF]. It is aimed at identifying population clusters respecting Hardy-Weinberg and linkage equilibriums. Further methods (e.g. ΔK method; [START_REF] Evanno | Detecting the number of clusters of individuals using the software STRUCTURE: A simulation study[END_REF] allow to identify the optimal number of clusters. The STRUCTURE method estimates allelic frequencies in each cluster and cluster memberships of each population/individual.

The phylogeography of P. fluviatilis was previously investigated in [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]. In this study, 55 European populations and one Siberian were studied using the mitochondrial Dloop and 35 populations were studied using three Random Amplification of Polymorphic DNA (RAPD). This work allowed highlighting four main groups (Figure 7): a southern European group (including Greek and southern Danubian populations), a western European group, an eastern European group which includes the Siberian populations, and a Norwegian group (which includes populations from northern Norway and western side of Oslofjord).

However, further investigations are required since (i) the former phylogeographic study was based on a small part of the mitochondrial genome, (ii) RAPD markers have been since

shown as limited and replaced by more powerful markers such as microsatellites [START_REF] Sunnucks | Efficient genetic markers for population[END_REF][START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF], and (iii) other studies were performed but investigated specific geographic areas (Table 9) and some discrepancies exists in conclusions between studies.

Therefore, due to limitations and discrepancies between conclusions, the phylogeographic structure of European perch needed to be further studied. As mentioned earlier, RAS is the most widespread culture system used for European perch production. Although this species started to be domesticated in the 1990s, there is still no consensus about the rearing conditions which should be used (diverse rearing conditions in the literature; Table 10), which makes comparisons between studies difficult [START_REF] Palińska-Żarska | Effect of water hardness, temperature, and tank wall color, on the effectiveness of swim bladder inflation and survival of Eurasian perch (Perca fluviatilis, L.) larvae reared under controlled conditions[END_REF][START_REF] Palińska-Żarska | Domestication process modifies digestion ability in larvae of Eurasian perch (Perca fluviatilis), a freshwater Teleostei[END_REF]. In 2017, before performing the second step of the integrative approach, we performed a survey regarding rearing conditions for European perch production and got answers from three perch farms. The number of answers was low but even with three farms we could state a high variability of rearing conditions (e.g. feeding protocol, tank shape and color, photoperiod) between farms. Therefore, the rearing conditions were based on a compromise between the literature, the survey results, and our own knowledge of European perch production techniques (Table 11). Most of the rearing conditions used are recognized as optimal for Percid larval culture (Policar et al. 2019 and references within). In this work, two independent experimental phases were performed in the bioassay studies:

phase I from hatching until the end of weaning (i.e. transition from live feed to inert pellets;

26 days post-hatching, dph) and phase II from 27 dph until the end of nursery, at 60 dph. The larval period was split in two phases in order to ensure availability of larvae across the whole larval period since there is a very high mortality rate during first-life stages. All experiments were conducted in cylindro-conical tanks (three cylindro-conical tanks per population corresponding to three replicates; Figure 8).  Specific Goal: Demonstrating that there is a geographic differentiation in Perca fluviatilis for other key traits than growth and developmental traits.

The first chapter of this thesis is aimed at evaluating if P. fluviatilis displays geographic differentiation for key traits in aquaculture conditions. Geographic differentiation had already been highlighted for several key traits, mostly related to growth and survival. Yet, behavioral traits are essential to study since they can facilitate or limit domestication and production [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]), but geographic differentiation was only shown previously in P. fluviatilis for cannibalism rate [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]). Therefore, this chapter focused on three behavioral parameters of interest for aquaculture: group structure, aggressive interaction rate, and activity. Tolerance to conspecifics in intensive rearing conditions is an essential parameter for production. Focusing domestication on populations which present an aggregative, homogenous, and cohesive group structure would be favoring welfare (Kristiansen et al. 2004). Moreover, aggressive interactions can lead to negative consequences in fish culture (e.g. mortalities, stress, immune suppression; [START_REF] Damsgård | Fighting and Aggression[END_REF]. Finally, activity is also an important trait to consider since it contributes to the total energetic budget of individuals [START_REF] Boisclair | The importance of activity in bioenergetics models applied to actively foraging fishes[END_REF]. This chapter brings another line of evidence that geographic differentiation can be helpful to facilitate domestication and production of P. fluviatilis. Taking into account results from previous studies and results from this chapter, geographic differentiation exists for several key traits and highlights the interest of using this species to develop and apply the three-step integrative approach.

INTRODUCTION

Increasing the agriculture sustainability, including aquaculture, relies partly on the production and domestication of new species [START_REF] Gepts | Biodiversity in Agriculture Domestication, Evolution, and Sustainability[END_REF]. Domestication is considered as the process in which populations are bred in man-controlled environment and modified across successive generations from their wild ancestors in ways making them more useful to humans who control, increasingly during the process, their reproduction and food supply [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]. However, domestication remains a difficult, long, and expensive process ridden by unfruitful outcomes, mostly due to zootechnical issues or taxon intrinsic features [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]. This is particularly acute in intensive aquaculture (i.e. nowadays, intensive monoculture is the primary aquaculture) in which many new species domestication trials are hampered by several bottlenecks and end up being abandoned [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]. For instance, some fish species display low resistance to diseases or low food conversion efficiency, which impede or slow down their domestication [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Otton | Establishment of an agribusiness model for assessing the commercial viability of new species for aquaculture[END_REF]). Conversely, other traits are favoring domestication such as fast growth rate and acceptance of artificial feeds, and consequently make taxon production an economically viable initiative [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] François | Considerations for the Selection and Commercialization of New or Alternate Species[END_REF]. Among these features, some behavioral traits are particularly essential since they can deeply facilitate domestication [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] François | Considerations for the Selection and Commercialization of New or Alternate Species[END_REF]) and subsequent aquaculture production [START_REF] Huntingford | Aquaculture and Behavior[END_REF]).

Among behavioral traits, inter-individual relationships, group structure, and activity can affect directly the ability of a species to be domesticated and efficiently produced in intensive monoculture conditions. Tolerance to conspecifics in a limited area is an essential parameter for production (Kristiansen et al. 2004) since it affects individual welfare [START_REF] Huntingford | Implications of domestication and rearing conditions for the behavior of cultivated fishes[END_REF][START_REF] Ashley | Fish welfare: Current issues in aquaculture[END_REF]). Selecting populations which present an aggregative and cohesive group structure, therefore limiting stress, would be favoring welfare. However, living in group is not costless as it can trigger for instance competition for resources [START_REF] Pitcher | Functions of Shoaling Behavior in Teleosts[END_REF][START_REF] Martins | Behavioral indicators of welfare in farmed fish[END_REF][START_REF] Ward | Sociality: The Behavior of Group-Living Animals[END_REF]. In culture conditions, this can lead to the emergence of aggressive behaviors [START_REF] Damsgård | Fighting and Aggression[END_REF], such as attacks or bites, leading in some cases to cannibalism [START_REF] Bandelt | Median-joining networks for inferring intraspecific phylogenies[END_REF]. These aggressive behaviors have several potentially negative consequences in fish culture such as mortalities, stress, immunesuppression, or uneven competition for food (Damsgård and Huntingford 2012 and references therein). Cannibalism (type I: prey is caught tail first and ingested partially; type II: prey is caught by the head or tail and fully ingested; [START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF][START_REF] Bandelt | Median-joining networks for inferring intraspecific phylogenies[END_REF]) is a major bottleneck in finfish aquaculture [START_REF] Naumowicz | Intracohort cannibalism and methods for its mitigation in cultured freshwater fish[END_REF] since it can lead to important losses [START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF][START_REF] Huntingford | Aquaculture and Behavior[END_REF]. For example, cannibalism can cause up to 50% losses in Perca fluviatilis [START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF][START_REF] Kestemont | Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: Biotic and abiotic influences[END_REF]. Finally, activity is also an important factor in aquaculture as it contributes to the total energetic budget (e.g. up to 40% of Perca flavescens budget; [START_REF] Boisclair | The importance of activity in bioenergetics models applied to actively foraging fishes[END_REF]. Moreover, less active taxa could contribute to lower potential contacts and subsequent potential aggressive interactions.

Therefore, in domestication processes, it is necessary to take into account the ability for taxa to present the most suitable group structure, low aggressive interaction rate, as well as lower activity. Yet, there is an intraspecific differentiation (differentiation between allopatric populations of conspecific individuals; Mayr 1963) which could further help to improve domestication processes.

Behavioral intraspecific differentiation and its potential for selection of founder populations have been poorly investigated to date. However, intraspecific differences in aggressive behavior [START_REF] Magurran | Variation in schooling and aggression amongst guppy (Poecilia Reticulata) populations in Trinidad[END_REF][START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF][START_REF] Bell | Behavioral differences between individuals and two populations of stickleback (Gasterosteus aculeatus)[END_REF]), time spent foraging in an open habitat [START_REF] Bell | Behavioral differences between individuals and two populations of stickleback (Gasterosteus aculeatus)[END_REF]Magnhagen 2006), schooling [START_REF] Magurran | Variation in schooling and aggression amongst guppy (Poecilia Reticulata) populations in Trinidad[END_REF], or boldness [START_REF] Wright | Inter and intra-population variation in shoaling and boldness in the zebrafish (Danio rerio)[END_REF] have been already assessed for a few species (see also [START_REF] Foster | The geography of behavior: an evolutionary perspective[END_REF]. Abiotic factors can influence social behaviors (e.g. temperature, light, population density; [START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF][START_REF] Kestemont | Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: Biotic and abiotic influences[END_REF]), yet a genetic basis was also suggested since allopatric populations or geographically distinct strain differentiations were demonstrated for a few species [START_REF] Amundsen | An experimental comparison of cannibalistic response in different Arctic charr (Salvelinus alpinus (L.)) stocks[END_REF][START_REF] Damsgård | Fighting and Aggression[END_REF][START_REF] Magnhagen | Behavioral responses in a net restraint test predict interrenal reactivity in Arctic charr Salvelinus alpinus[END_REF]. Therefore, considering such behavioral intraspecific differentiation could allow improving aquaculture for species for which production is still limited by behavioral bottlenecks.

The European perch, Perca fluviatilis L., is one of the fish species involved in the European aquaculture diversification (Kestemont et al 2015a). Its long standing socio-economic interest (high market value and recreational interest) led to the development of its aquaculture in the 90's [START_REF] Kestemont | Chap. 11 -Aquaculture[END_REF]Kestemont et al. 2015a). However, its production is still limited due to several bottlenecks including some aspects related to fish behavior such as aggressiveness and high cannibalism and subsequent mortalities (Kestemont et al. 2015a).

However, geographic differentiation has been previously observed for some of problematic behavioral traits (e.g. cannibalism rate, [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]). Therefore, we aim in this study at (i) assessing if European perch allopatric populations present differentiation for group structure and activity, as well as for aggressive interactions during first-life stages, and (ii) identifying populations presenting behavioral advantages for production.

MATERIAL AND METHODS

Rearing conditions

Rearing parameters were chosen according to trade-offs between abiotic culture conditions used in literature (e.g. [START_REF] Vlavonou | Elevage expérimental de la perche Perca fluviatilis L.: développement larvaire et croissance[END_REF][START_REF] Kestemont | Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: Biotic and abiotic influences[END_REF]Kestemont et al. 2015a), our practices, and fish farming practices. The rearing protocol was tested and validated with a domesticated population from the fish farm "Lucas Perches" (Hampont, France) comparing growth and survival results to literature (e.g. [START_REF] Vlavonou | Elevage expérimental de la perche Perca fluviatilis L.: développement larvaire et croissance[END_REF][START_REF] Fiogbé | Optimum daily ration for Eurasian perch Perca fluviatilis L. reared at its optimum growing temperature[END_REF].

Egg ribbons were obtained during the 2018 spawning season (May 2018) from lakes Geneva (GEN; Switzerland; 46°26′N, 6°33′E), Valkea-Müstajärvi (VAL; Finland; 61°13'08"N, 25°07'05"E), and Iso-Valkjärvi (ISO; Finland; 60°57'21"N, 26°13'3"E). After transport, 19 egg ribbons per lake were incubated at the Experimental Platform of Aquaculture (Unit of Animal Research and Functionality of Animal Products, University of Lorraine, Vandoeuvrelès-Nancy, France) in incubators (110x64x186cm; one incubator per population), containing nine racks each (45x7x12cm), at 13°C. Each incubator had its own temperature control and recirculated water (flow rate of 4m 3 .h -1 ) system and water was UV sterilised. Oxygen rate (10.5 ± 0.2mg.L -1 ) and temperature (13.0 ± 0.3°C) were checked daily while pH was measured three times a week (8.0 ± 0.1). Ammonium (lower than 0.05mg.L -1 ) and nitrite concentrations were monitored three times a week until hatching (lower than 0.01mg.L -1 ).

Photoperiod was 12L:12D and light intensity was 400 lx at the water surface.

Two independent experiments were performed in order to ensure availability of larvae across the rearing period: experiment I from hatching until the end of weaning (26 days posthatching, dph) and experiment II from 27 dph until 60 dph. All populations were reared in independent structures.

Concerning experiment I, after hatching, larvae from the different egg ribbons were mixed and transferred to three green internal-wall 71L cylindro-conical tanks (three replicates per population; recirculated aquaculture system (RAS)) at a density of 50 larvae.L -1 . Temperature was gradually increased during two weeks to 20°C, photoperiod was 12L:12D and light intensity was 400lx. Larvae were fed with newly hatched Artemia naupli (Sep-Art, INVE) every 1h30 from 3 dph until weaning. At 16 dph, Artemia ration was decreased by 25% every three days and dry feed ration (BioMar, 300µm until 21 dph, then 500µm) was increased by the same ratio. After 25 dph, larvae were only fed with dry feed ad libitum (BioMar 500µm, then 700µm at 44 dph until the end of the experiment). At 26 dph, the larvae in cylindroconical tanks were removed to start experiment II.

For experiment II, larvae not used for experiment I were held after hatching in 2m 3 tanks (RAS) under the same temperature, feeding, light intensity, and photoperiod regimes as individuals of the experiment I. At 27 dph, these larvae were transferred at a density of 19 larvae.L -1 to the three cylindro-conical tanks in order to start experiment II. Light intensity was 80 lx at water surface, all else remaining equal to experiment I (except for density).

During the two experiments, oxygen concentration (8.7 ± 2.3mg.L -1 ) and temperature (20.0 ± 0.6 °C) were checked daily for all tanks. Ammonium (0.14 ± 0.1 mg.L -1 ), pH (7.2 ± 0.9 mg.L - 1 ), and nitrite concentrations (0.08 ± 0.08 mg.L -1 ) were monitored three times a week. Tanks were cleaned daily after first feeding and dead individuals were removed every morning.

Survival rate for ISO, VAL and GEN were respectively 40.1 % (± 12.0), 29.4 % (± 14.5) and 6.6 % (± 3.4) for experiment I (26 dph; statistical difference between Geneva Lake and the two Finnish populations; F=7.2, df=2, P<0.05) and 31.5 % (± 4.3), 28.0 % (± 11.1) and 37.4 (± 8.1) for experiment II (60 dph; no statistical difference between the three populations; F=0.98, df=2, P=0.42)). These ranges of survival rates were comparable to what is found in literature (e.g. [START_REF] Tamazouzt | Tank wall color and light level affect growth and survival of Eurasian perch larvae (Perca fluviatilis L.)[END_REF][START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF][START_REF] Fiogbé | Optimum daily ration for Eurasian perch Perca fluviatilis L. reared at its optimum growing temperature[END_REF].

Group structure and activity

For each population, three replicates for each cylindro-conical tank were performed over two days (25 and 26 dph). At 24 and 25 dph, a total of 90 individuals (n=30 for each cylindroconical tank, 10 individuals per replicate) were sampled for each population and transferred to three aquaria (58 L; one aquarium per cylindro-conical tank; order of cylindro-conical replicates randomly assessed over two days; see appendix 1) with an 80lx light intensity and a temperature of 20.0°C (± 0.5). Individuals were not fed from the moment they were transferred to the beginning of the experiment the following day in order to have individuals in the same energetic state. After one night of acclimatisation, individuals were tested by groups of ten in circular arenas. Groups of ten individuals might not reflect faithfully what occurs in cylindro-conical tanks. However, evaluation cannot be performed directly in the tanks and this method was previously validated (e.g. [START_REF] Colchen | Temperature modifies activity, inter-individual relationships and group structure in fish[END_REF]. Three circular arenas (30 cm diameter with 1.5cm of water depth) were used to investigate group structure and activity [START_REF] Colchen | Temperature modifies activity, inter-individual relationships and group structure in fish[END_REF]. Water in the arena was the same as in the aquaria, room temperature was maintained at 20.0 °C (± 0.6) and arenas were lit at 10lx from underneath in order to avoid shadows during recording. For each replicate, individuals were transferred from the aquarium to the arena with a beaker and a siphon. After 30min acclimatisation, individuals were filmed for 30min using camcorders (Sony, Handycam, DCR-SR72E) located 50cm above the arena. The three arenas were filmed simultaneously and the order of replicates tested was randomly assessed. Group structure analysis was performed using the ImageJ software. Images were extracted from videos at 3-min interval (11 images per video). From each image, exact coordinates of each individual were noted using the middle point between the eyes. Three parameters were evaluated to assess the group structure: the nearest neighbour distance, the mean of interindividual distances, and the variance of these inter-individual distances (Buske and Gerlai 2011a). Nearest neighbour distance represents the distance between a focal fish and its closest neighbour and is an indicator of the group aggregation. The mean of inter-individual distances corresponds to the mean of distances between a focal fish and all the other fish of the group and the average of values from all group members is an indicator of the group cohesion.

Finally, the average of variances of inter-individual distances from each fish represents the homogeneity of distribution (Buske and Gerlai 2011a). Activity was also calculated in ImageJ. One image per second was extracted for six consecutive seconds every five minutes.

Coordinates of each individual were noted for each image and then distance swam was calculated every second during the five seconds then averaged to obtain the mean distance swam for each individual per second.

All statistical analyses were performed in R 3.0.3 (R Core Team 2017). To test the normality of distributions, a Shapiro-Wilk test (R Core Team 2017) was used and homogeneity of variances was tested using the Levene test [START_REF] Gastwirth | Lawstat -Tools for Biostatistics[END_REF]. Then, linear mixed models were used with distances and activity as fixed factors and cylindro-conical tanks as random factor [START_REF] Bates | Twenty years of phylogeography: the state of the field and the challenges for the Southern Hemisphere[END_REF]). There was no influence of the cylindro-conical tank on all models.

Therefore, one-way analyses of variance (ANOVA F test) followed by Tukey post hoc tests were used to evaluate differences between populations (R Core Team 2017).

Quantification of aggressive interactions

Daily observations were carried out at different moments of the day previous to this experiment but did now allow identifying a cannibalism peak during the photophase.

Therefore, we hypothesised that the beginning of the photophase would correspond to the cannibalism peak since individuals were not fed between 5.30pm and the next morning, that they were used to be fed during the photophase and that European perch is a visual predator [START_REF] Graeb | Foraging behavior, morphology, and life history variation determine the ontogeny of piscivory in two closely related predators[END_REF][START_REF] Kestemont | Larval and juvenile production[END_REF]. Therefore, observations were performed after first feeding with a five-minute acclimatisation to the presence of the observer and five minutes of focal sampling [START_REF] Colchen | Intra-cohort cannibalism in early life stages of pikeperch[END_REF]. Daily observations were carried out between 8.30am and 10am from 10 dph until the end of experiment I (26 dph). For experiment II, observations were carried out every three days (see Appendix 1). One replicate per population was observed per day and the same person performed all observations. Since hatching times were asynchronous between populations, the order of populations or tanks observed were randomly assigned. Several aggressive behaviors were noted: (i) Pursuit: an individual heads towards a conspecific, gets close and follows it when the conspecific moves; this involves a change of direction of the two individuals, (ii) Attack: when an individual heads towards a congener and gets rapidly close to it without necessarily contact between the two individuals, (iii) Bite:

when an individual catches with its mouth a part of a conspecific's body and then releases it, and (iv) Capture: when an individual ingests a part or the whole conspecific (type I and II cannibalisms). Taking into account all these aggressive interactions, a global daily aggressive interaction rate was calculated relatively to the initial number of individuals in the tank.

Enucleation, being a specific indicator of aggressiveness in perch [START_REF] Jourdan | Influence of daylength on growth, heterogeneity, gonad development, sexual steroid and thyroid levels, and N and P budgets in Perca fluviatilis[END_REF], was also evaluated by counting daily the number of dead individuals enucleated. Enucleation rate was calculated relatively to the initial number of individuals in the tank. For phase II, type II cannibalism rate was estimated by subtracting from the initial number of individuals the number of survivors and dead individuals over phase II and calculating a rate relatively to the initial number of individuals in the tank. Cannibalism rate could not be evaluated for experiment I as a precise monitoring of mortality was not possible the first week due to fast degradation of dead larvae. Finally, mortality rates attributed to cannibalism and enucleation were also calculated. In order to meet assumptions of normality (Shapiro-Wilk test, R Core

Team 2017) and homogeneity of variances (Levene test, [START_REF] Gastwirth | Lawstat -Tools for Biostatistics[END_REF], data for all aggressive parameters was transformed (i.e. log(x+1)). One-way analyses of variance (ANOVA F test) followed by Tukey post hoc tests were used to evaluate differences between populations (R Core Team 2017). When assumptions were not respected (only for the aggressiveness rate during experiment I), Kruskal-Wallis H tests (R Core Team 2017) were used followed by Dunn post-hoc tests [START_REF] Pohlert | Recent progress in European percid fish culture production technology-tackling bottlenecks[END_REF].

Compliance with ethical standards

All along experimental procedures, individuals were handled as little as possible. All procedures were in accordance with the national and international guidelines for protection of animal welfare (Directive 2010/63/EU). This study was conducted with the approval Animal Care Committee of Lorraine (CELMA n°66) and the Ministry of Higher Education, Research, and Innovation (APAFIS13368-2018020511226118).

RESULTS

Group structure and activity

Experiment I (25-26 dph)

Inter-individual distances (F=7.8, df=2, P<0.05), variance of inter-individual distances (F=9.9, df=2, P<0.05), and activity (F=8.2, df=2, P<0.05) are significantly lower for GEN compared to VAL and ISO (Fig. 1). There is no statistical difference between VAL and ISO.

There is no statistical difference between populations for the nearest neighbour distance (F=1.4, df=2, P=0.2; Fig. 1).

Experiment II (45-46 dph)

Inter-individual distances (F=7.8, df=2, P<0.05) and variance of inter-individual distances (F=9.9, df=2, P<0.05) are significantly higher for GEN compared to VAL and ISO (Fig. 2).

There is no statistical difference between ISO and VAL. There is no statistical difference between populations for the nearest neighbour distance (F=1.4, df=2, P=0.3) and activity (F=1.2, df=2, P=0.3; Fig. 2).

Quantification of aggressive interactions

The first cases of cannibalism (type II only) were observed at 26 dph for ISO and at 51 dph for GEN. No cannibalism case was observed for VAL. There is no difference of daily aggressive interaction rate in experiment I (H=0.60, df=2, P=0.74; Fig. 1) but in experiment II these behaviors were significantly higher in GEN than ISO and VAL (F=7.21, df=2, P<0.05;

Fig. 2).

There is no statistical difference between ISO and VAL. Enucleation rate, which is null in experiment I for all populations, is significantly higher in GEN compared to VAL and ISO (F=70.74, df=2, P<0.05; Fig. 2) in experiment II. Cannibalism rate is not statistically different between populations (F=0.018, df=2, P=0.98; Fig. 2). Mortality rate attributed to cannibalism and enucleation is not statistically different between the three populations (F=0.69, df=2, P=0.59; Fig. 2).

DISCUSSION

Inter-populational differentiation in behavioral traits and its potential causes

In this study, we highlight intraspecific differentiation between the two Finnish populations and GEN for group structure (experiments I and II) and aggressive interactions (only experiment II) while activity does not differ. We cannot exclude some potential biases in our experiments. For instance, (i) aggressive behavior observations have been made after first feeding but cannibalism peaks (and aggressions) might occur at different moments of the day between populations and (ii) calculated cannibalism rate might also include dead individuals eaten by conspecifics which can blurry differences in cannibalism rates. However, since (i)

temporal differentiation in cannibalism peaks has not been reported to date and (ii) the cannibalism estimation method, widely used across literature (e.g. [START_REF] Kestemont | Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: Biotic and abiotic influences[END_REF][START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]), allows to compare populations, we argue that bias related to observations of inter-populational behavioral differentiations at two ages are limited.

Intraspecific differentiation in group structure and aggressive behaviors has been already highlighted for several fish species [START_REF] Rosenau | Inherited differences in agonistic behavior between two populations of coho salmon[END_REF][START_REF] Magurran | Variation in schooling and aggression amongst guppy (Poecilia Reticulata) populations in Trinidad[END_REF][START_REF] Amundsen | An experimental comparison of cannibalistic response in different Arctic charr (Salvelinus alpinus (L.)) stocks[END_REF][START_REF] Lahti | Variation in aggressive behavior and growth rate between populations and migratory forms in the brown trout, Salmo trutta[END_REF][START_REF] Huizinga | The genetic and environmental basis of adaptive differences in shoaling behavior among populations of Trinidadian guppies, Poecilia reticulata[END_REF][START_REF] Wark | Heritable differences in schooling behavior among threespine stickleback populations revealed by a novel assay[END_REF][START_REF] Song | Interpopulation differences in shoaling behavior in guppies (Poecilia reticulata): Roles of social environment and population origin[END_REF]). Here, a more cohesive and homogeneous structure is demonstrated for Finnish populations compared to GEN at 45-46 dph (Fig. 2). These results, associated with a similar nearest neighbour distance, indicate a structure in sub-groups in all populations but with a distance between these groups higher for GEN at 45 dph. The less homogeneous group structure of GEN at 45 dph is quite congruent with the higher aggressiveness highlighted for this population. Indeed, although daily aggressive interaction rate seems low (0.1-0.9 %; Fig.

2), the congruence between aggressive interaction patterns and enucleation rate supports the higher aggressiveness of GEN compared to the two Finnish populations. The absence of difference in cannibalism rate indicates that aggressive interactions are not necessarily followed by type II cannibalism. Therefore, our study is not congruent with [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF] who showed a difference in intra-cohort cannibalism rate between different European perch allopatric populations (but with different populations than the ones investigated here).

Here, we highlight differences in aggressive interactions aside from cannibalism rate. Interpopulational behavioral differences can be shaped by genetic differentiation, by phenotypic plasticity, or by their combination.

On the one hand, the observed inter-populational behavioral differences could be shaped by genetic differentiation. Indeed, population-specific demographic histories and potential local adaptations fostered by particular selective pressures can lead to the acquisition of distinct behavioral phenotypic traits or development rates between allopatric conspecific populations [START_REF] Foster | Geographic variation in behavior : perspectives on evolutionary mechanisms[END_REF][START_REF] Foster | The geography of behavior: an evolutionary perspective[END_REF]. For instance, it was shown a link between aggressiveness and the level of predation of the natural living site [START_REF] Huntingford | Do inter-and intraspecific aggression vary in relation to predation pressure in sticklebacks?[END_REF][START_REF] Magurran | Variation in schooling and aggression amongst guppy (Poecilia Reticulata) populations in Trinidad[END_REF] as well as other environmental factors such as food availability and water current velocity (Lahti et al. 2001 and references therein). The occurrence of inherited differences in aggressive interactions was assessed for several species [START_REF] Huntingford | Aquaculture and Behavior[END_REF][START_REF] Damsgård | Fighting and Aggression[END_REF]. Similarly, inter-populational differences in activity were found to be connected to prey size distribution, total prey biomass, and water transparency [START_REF] Boisclair | The importance of activity in bioenergetics models applied to actively foraging fishes[END_REF]. Unfortunately, we do not have enough information on the different lakes abiotic and biotic parameters to make any assessment. Another explanation of inter-populational differences could be divergences in development rates potentially triggered by genetic specificities. Indeed, we compare the populations at the same age but we do not know if the compared fishes are at the same developmental stage (i.e. the lack of development table for larval and juvenile stages of P. fluviatilis prevent us to assess if the development is synchronous between populations). The populations might have divergent development rates, which can trigger inter-populational differences in parameters investigated. For instance, the higher aggressiveness in experiment II might be related to the development of muscular and nutritional structures through the larval stage [START_REF] Kestemont | Nutritional and animal husbandry aspects of rearing early life stages of Eurasian perch Perca fluviatilis[END_REF][START_REF] Vlavonou | Elevage expérimental de la perche Perca fluviatilis L.: développement larvaire et croissance[END_REF]. It can also be related to the development of visual structures since the visual acuity, essential for capture of prey, increases until metamorphosis (Guma'a 1982). In addition, the aggregation in sub-groups might be due to several factors such as kinship [START_REF] Behrmann-Godel | Kin and population recognition in sympatric Lake Constance perch (Perca fluviatilis L.): can assortative shoaling drive population divergence?[END_REF], the nature of interactions (e.g. aggressive interactions), spatial distribution, or differential sizes [START_REF] Hinde | Interactions, Relationships and Social Structure[END_REF]. Since these two last factors are sensitive to developmental stage, group structure is also influenced by development rate.

On the other hand, phenotypic plasticity (i.e. the ability of a genotype to produce more than one phenotype when exposed to different environments; [START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF][START_REF] Kelly | Phenotypic plasticity: molecular mechanisms and adaptive significance[END_REF]) is an alternative explanation of the observed behavioral differentiations between populations (DeWitt and Scheiner, 2004) with behavior reflecting the strategy adopted under the influence of environmental factors. This was suggested as the driving factor for cannibalism in P. fluviatilis (Król et al. 2015 and references therein) as well as in other species (e.g. [START_REF] Svenning | Cannibalism in Arctic charr: do all individuals have the same propensity to be cannibals?[END_REF]. Since we have used an experimental transplant approach (common environment), we speculate that we have minimized the effect of the environment (West-Eberhard 2003). Nevertheless, influences of past environmental conditions (i.e. before the beginning of our experiment) cannot be ruled out. On the one hand, we have collected individuals at the egg stage in the wild and phenotypic response to environmental conditions could have occurred during development [START_REF] Swain | Meristic variation in a clone of the cyprinodont fish Rivulus marmoratus related to temperature history of the parents and of the embryos[END_REF]. On the other hand, environmental conditions experienced by the parents might have influenced offspring phenotype [START_REF] Mousseau | The adaptive significance of maternal effects[END_REF][START_REF] Youngson | Transgenerational epigenetic effects[END_REF]. At last, it was also shown an influence of maternal size on larvae performance [START_REF] Olin | Importance of maternal size on the reproductive success of perch, Perca fluviatilis, in small forest lakes: Implications for fisheries management[END_REF]).

Since we have no information on the parents of egg sampled, we cannot exclude the influence of maternal effects which were demonstrated in P. fluviatilis for other traits [START_REF] Mandiki | Initial weight and its variation in postlarval Eurasian perch affect quantitative characteristics of juvenile cohorts under controlled conditions[END_REF]Król et al. 2015).

Overall, we cannot assess the importance of genetic differentiation, phenotypic plasticity, and specific development rates in population-specific behavior. Behavioral differentiation might be the result of the interaction of all factors (see for instance for cannibalism, [START_REF] Baras | Dynamics of intracohort cannibalism in cultured fish[END_REF][START_REF] Yang | To what extent is cannibalism genetically controlled in fish? A case study in juvenile hybrid catfish Silurus meridionalis-asotus and the progenitors[END_REF]. Moreover, effects of experience on behavior cannot be ruled out as it was previously suggested as an important factor for the behavioral variation [START_REF] Hellström | The influence of experience on risk taking: results from a common-garden experiment on populations of Eurasian perch[END_REF][START_REF] Magnhagen | Behavior of percid fishes in the wild and its relevance for culture[END_REF]. Further analyses over several generations with populations under identical rearing conditions as well as the establishment of a development table for larval and juvenile stages of P. fluviatilis are needed to assess the importance of each factor in the geographic differentiation of behavior.

Differences in group structure and aggressive interactions between the two different ages

For each population, we observe a behavioral differentiation between the two studied ages.

Such a differentiation has been previously observed in other species. For instance, development of shoaling (increasing protection against predators, foraging efficiency, and mate encounters) with age through a decrease of inter-individual and nearest neighbour distances has already been observed in zebrafish (Buske and Gerlai 2011b;[START_REF] Buske | Maturation of shoaling behavior is accompanied by changes in the dopaminergic and serotoninergic systems in zebrafish[END_REF]. We observe similar development for ISO and VAL populations. In contrast, the opposite pattern observed for GEN population is unexpected and corresponds to the establishment of a less homogeneous group with age. Mechanisms underlying the agedependant changes in group structure are so far unknown. Differential ontogenies of sensory development might play a role into differences at the different ages [START_REF] Buske | Maturation of shoaling behavior is accompanied by changes in the dopaminergic and serotoninergic systems in zebrafish[END_REF].

Several neuroanatomical, physiological or biochemical factors have been suggested to be involved [START_REF] Buske | Maturation of shoaling behavior is accompanied by changes in the dopaminergic and serotoninergic systems in zebrafish[END_REF]. There might also be some group regulation mechanisms subsequent to weaning, which can potentially increase competition for resources linked for instance to bioenergetic needs or physiological shifts. This competition could explain the higher occurrence of aggressive interactions in experiment II.

Integrating inter-populational behavior differentiation: a way to improve aquaculture production?

The variability occurring in behavior at the intraspecific level offers the opportunity to select fishes whose behaviors make them more suitable for aquaculture production (Huntingford et al. 2012). In the European perch, the lack of population-specific activity tends to make this trait useless to select best population for aquaculture purpose. In contrast, difference in aggressiveness (i.e. and its consequences: losses due to aggressive interactions ranged from about 20% to 40% depending on the population; experiment II, Fig. 2) is a potential selection criterion for farmers since such interactions are highly detrimental for fish production.

Similarly, the population-specific group structure should be considered as highly important information to highlight most suitable populations for intensive aquaculture. Based on our result, the more cohesive group structure and less aggressive interactions of Finnish P.

fluviatilis make them the most suitable populations for aquaculture. However, more populations need to be compared in order to identify populations of interest across the species range. Moreover, we cannot exclude the future potential impact of domestication since behavioral traits are modified by this process [START_REF] Kohane | Domestication: evolutionary change under stress[END_REF]). Yet, taking into account behavioral intraspecific differentiation would allow starting domestication program on populations presenting the best behavioral pre-disposition.

Selecting best populations for aquaculture production cannot be made through only behavioral trait comparisons. Indeed, selective breeding for low stress responsiveness has for instance been applied in several fish species but these low-stress response fish were also the ones which were more aggressive [START_REF] Huntingford | Aquaculture and Behavior[END_REF]. Intraspecific differentiation has been already assessed for several other traits of interest such as growth (e.g. [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF][START_REF] Leithner | Rearing larvae of different strains of Coregonus lavaretus under cold water conditions: comparison of a special cold-water line with a standard agglomerated microdiet[END_REF], feed conversion efficiency (e.g. [START_REF] Imsland | Congress proceeding[END_REF][START_REF] Jonassen | Geographic variation in growth and food conversion efficiency of juvenile Atlantic halibut related to latitude[END_REF], or disease resistance (e.g. [START_REF] Imsland | The interrelation of growth and disease resistance of different populations of juvenile Atlantic halibut (Hippoglossus hippoglossus L.)[END_REF][START_REF] Overturf | Comparison of growth performance, immunological response and genetic diversity of five strains of rainbow trout (Oncorhynchus mykiss)[END_REF].

Therefore, the choice of the founder population must then be based on a multi-function and multi-traits approach rather than a single-trait decision framework.

APPENDIX Appendix 1:

Material and methods workflow.

TAKE HOME MESSAGE

We demonstrated a geographic differentiation for aggressive interactions and group structure between three allopatric larval populations of Perca fluviatilis.

The differentiation in behavioral parameters is lower between the two Finnish populations (VAL and ISO) than when compared to Lake Geneva.

These results highlight the potential usefulness of considering geographic differentiation for P. fluviatilis domestication and production.  Specific Goal: Conceptualizing a method to integrate geographic differentiation in domestication processes in order to facilitate new species domestication and production.

One way to facilitate the domestication and production of new species may consist in considering wild geographic differentiation. This chapter is aimed at finding a way to integrate geographic differentiation in domestication processes. This chapter proposes a standardized conceptual approach to achieve this objective. This approach relies on three steps: (i) classifying wild populations of a species of concern in prospective units which are likely divergent for key traits in aquaculture, (ii) comparing performances of these prospective units through a multi-function and multi-trait approach in a common garden experiment (i.e.

in an environment corresponding to the culture system), and (iii) calculating an aquaculture potential index to identify units of high potential for aquaculture within species to start new domestication processes. One challenge of this chapter was also to define what can be considered as key traits for domestication and subsequent production. Key traits were classified in four categories.

CONTEXT

Aquaculture is the farming of aquatic organisms through several alternative practices (i.e. monoculture/polyculture, outdoor/indoor, flow through systems/recirculated systems, and extensive/intensive). Since the 1960s, aquaculture production has rapidly expanded and exponentially grown worldwide as far as to provide more than 50% of the world's aquatic food consumption nowadays (FAO 2018). This development has been triggered by the need to meet the increasing human demand for aquatic products since wild fisheries catches are no longer sufficient [START_REF] Watson | Systematic distortions in world fisheries catch trends[END_REF][START_REF] Froese | What catch data can tell us about the status of global fisheries[END_REF]. Nevertheless, aquaculture is often criticized due to its negative environmental impacts and its potential unsustainable development (Martinez-Porchas and Martinez-Cordova 2012; [START_REF] Christou | Sustainable Food Production[END_REF][START_REF] Diana | Responsible Aquaculture in 2050: Valuing Local Conditions and Human Innovations Will Be Key to Success[END_REF]). The low species diversity which contributes to worldwide aquaculture production is one of the main causes of these issues. Indeed, although numerous species have been farmed, the production of most of these species (i) was quickly abandoned due to zootechnical or economic problems or (ii) remains marginal when compared to the total volume of aquaculture production [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]. Thereby, 85% of the current world fish production relies on about fifteen species [START_REF] Lazard | Les paradoxes et les questionnements soulevés par l'exploitation de la biodiversité (autochtone et introduite) en aquaculture[END_REF]. Such production model based on few species, jeopardizes (i) local native fish fauna by increasing interspecific competition in the wild [START_REF] Garibaldi | The database on introductions of aquatic species (DIAS): the web site[END_REF][START_REF] Silva Ss De | Alien Species in Aquaculture and Biodiversity: A Paradox in Food Production[END_REF] or triggering pathogen spillover (Martinez-Porchas and Martinez-Cordova 2012) when accidental introductions or invasions by the alien farmed species happen, (ii) human food security since the heavy dependence on few species puts at risk aquaculture production (e.g. if an epizootic outbreak happens in farmed species, see for instance Godoy et al. 2008), and (iii) economic prospect since poorly diversified production limits the adaptive potential of aquaculture to face environment/consumer demand changes [START_REF] Fontaine | Développement de la pisciculture continentale européenne et domestication de nouvelles espèces[END_REF][START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]. In face of such threats, international organizations (e.g. the Food and Agriculture

Organization of the United Nations) are strongly advocating for diversification in regard to species while strengthening well-established species (FAO 2018;[START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]. Indeed, species diversification appears as one way to improve the sustainability of the aquaculture sector and promote its resilience, particularly through the production of new species occupying other market segments, for instance niche markets [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Muir | Managing to harvest? Perspectives on the potential of aquaculture[END_REF][START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF]FAO 2018;[START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]. This political will has triggered the development of new species production (e.g. DIVERSIFY project

[https://www.diversifyfish.eu/], [START_REF] Aruho | An overview of domestication potential of Barbus altianalis (Boulenger, 1900) in Uganda[END_REF][START_REF] Mitra | An overview of biology and culture potentials of humped featherback Chitala chitala (Hamilton, 1822) -A new candidate for aquaculture diversification[END_REF].

One of the biggest challenges in aquaculture diversification is the required domestication of wild taxa [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Harache | Development and diversification issues in aquaculture. A historical and dynamic view of fish culture diversification[END_REF][START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF]. Domestication is the process in which some populations are bred in a human-controlled environment and modified across successive generations from their wild ancestors in ways making them more useful to humans who control increasingly during the process their reproduction and food supply [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]. This is a stepwise process (i.e. the domestication levels sensu Teletchea and [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]). In contrast, most of already domesticated and fruitfully produced species display the opposite expression pattern for these traits [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF]. Other intrinsic features can also be important in some particular human-controlled environments such as the ability to tolerate high rearing densities in intensive culture [START_REF] Jobling | Farmed species and their characteristics[END_REF] or the resistance to environmental disturbances occurring in outdoor aquaculture [START_REF] Ficke | Potential impacts of global climate change on freshwater fisheries[END_REF]). This means that some species might be suitable for a particular rearing system but would poorly perform in another. Overall, a successful domestication requires the favorable expression of traits involved in several biological functions or intrinsic characteristics (i.e. trait not associated to a specific biological function)

of the targeted species. Indeed, a group of individuals can be domesticated if it can reproduce (reproductive and behavior functions), grow (growth, development, and behavior functions), feed (nutrition and behavior functions), and overcome stresses (e.g. resistance to diseases, immune, and behavior functions) in a particular controlled environment. Besides these traits, the costly domestication process of a wild taxon cannot be achieved without stakeholders' support and/or interest [START_REF] Suquet | A systematic market approach to species diversification : a French case study[END_REF], highlighting the importance of considering other traits involved in the socio-economic context (e.g. product quality traits). Overall, all of these factors shape the so called aquaculture potential: a quantification of how much expression of all key traits/functions (biological and socio-economic traits) is favorable for domestication and subsequent production. Therefore, the aquaculture potential assessment requires a multifunction and a multi-trait evaluation. Beside the species intrinsic aquaculture potential, domestication of a taxon is unlikely if the human needs that it could meet are already addressed (e.g. by other currently domesticated species [START_REF] François | Considerations for the Selection and Commercialization of New or Alternate Species[END_REF] or when capture fisheries already fulfil consumer demand for a particular species, e.g. [START_REF] Otterå | Cultured Aquatic Species Information Program[END_REF]).

The differential species suitability for domestication programs places a premium on the development of an approach to find relevant candidates in the wild biodiversity. Highthroughput screening of the wild biodiversity has recently been proposed as a solution to highlight such species in crops by testing many wild candidate taxa [START_REF] Dehaan | A pipeline strategy for grain crop domestication[END_REF]).

These candidates are tested across several steps including a first step of screening wild species to identify candidates of interest through an evaluation of traits linked to several biological functions (e.g. growth rate, yield, suitability for special diets; DeHaan et al. 2016). Similar approaches, although less developed, are also available for fishes and consider wild fish biological characteristics as well as socio-economic traits in the evaluation process (e.g. Le [START_REF] Lazard | Les paradoxes et les questionnements soulevés par l'exploitation de la biodiversité (autochtone et introduite) en aquaculture[END_REF][START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF]. Nevertheless, such approaches often consider species as a unity and disregard wild inter-populational geographic differentiation (sensu divergence between allopatric groups of conspecifics; [START_REF] Mayr | Animal species and evolution[END_REF] and its consequences on aquaculture potential.

WILD INTRASPECIFIC DIFFERENTIATION: AN ASSET FOR FISH FARMING?

Inter-populational geographic differentiation is a common phenomenon in fish species (see [START_REF] Bernatchez | Comparative phylogeography of Nearctic and Paleartic fishes[END_REF][START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF] which could be important for new domestication programs. Indeed, allopatric populations can undergo specific demographic histories as well as geographic and ecologic isolation triggering (i) gene flow disruption or limitation and subsequently genetic divergence and (ii) local adaptations to different selection regimes [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]. Ultimately, this shapes local specificities in genetic, morphology, physiology, behavior, and/or ecology which could impact the aquaculture potential and economic attractiveness of each wild population (e.g. for non-fish species in Lecocq et al. 2016a,b).

In non-fish species, geographic differentiation of important traits for domestication and production is known for several wild species of interest such as plants (e.g. [START_REF] Mansour-Gueddes | Agronomic and chemical evaluation of seven hot pepper (Capsicum annuum L.) populations grown in an open field[END_REF][START_REF] Healey | The Hops List[END_REF]) and fungi (e.g. [START_REF] Liti | Population genomics of domestic and wild yeasts[END_REF][START_REF] Warringer | Trait variation in yeast is defined by population history[END_REF].

Moreover, a few previous success stories show that the best candidates to start new species production are not a particular species but rather one or some particular groups of populations within the species of concern for a particular culture system. The bumblebee production industry provides one remarkable example where population-specificity inclusion through multi-trait evaluation in domestication programs fostered a fruitful economic development [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF]Lecocq et al. 2016a,b). One species, the buff-tailed bumblebee (Bombus terrestris) displays significant differentiation in key traits for bombiculture (i.e.

foraging efficiency, behavior, colony size, diapause condition, and phenology) between allopatric groups of populations corresponding to subspecies (reviewed in Lecocq et al. 2016b). In the early years of production, European bumblebee breeders tried to domesticate several subspecies [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF]. Within a fairly short amount of time, one of these subspecies proved to have superior characteristics from a commercial point of view and has become the dominant taxa in the bumblebee production industry (Lecocq et al. 2016b).

In fish production, geographic differentiation has been poorly considered at the beginning of new wild fish domestication trials. However, the few examples involve some of the most successful fish productions. In the 1970s, 41 wild Scandinavian salmon (Salmo salar)

populations were bred in a standardized production environment to evaluate their performances [START_REF] Gjedrem | Genetic origin of Norwegian farmed Atlantic salmon[END_REF]. This work considered, on different year classes, several desirable traits (e.g. growth, age at sexual maturity, furunculosis resistance, filet color) in order to identify the best populations to be used for production (which greatly improved salmon production, [START_REF] Gunnes | Selection experiments with salmon IV Growth of Atlantic Salmon during two years in the sea[END_REF]Gjedrem 1978, Gjedrem et al. 1991;[START_REF] Gjedrem | The first family-based breeding program in aquaculture[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF].

Later, in the 1990s, four Middle Eastern and Asian farmed populations along with four wild allopatric African populations of Nile tilapia (Oreochromis niloticus) were crossbred to produce fish stocks [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]). Among these fish, best breeders (i.e.

with highest growth rate) were selected to develop the genetically improved farmed tilapia strain that grows up to 85% faster than the earlier farmed fish stocks and is now disseminated across the world [START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF].

Conversely to the bumblebee example, the Scandinavian salmon and Nile tilapia cases only show how the geographic differentiation can be useful for advanced fish domestication programs. Here, we argue that fish domestication programs could take advantage of geographic differentiation to initiate or to continue the earlier levels of the domestication process (i.e. levels from one to three, and possibly four, see levels in [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]. Indeed, non-domesticated or species at incipient domestication levels display, when bred in captive conditions, differentiation for several traits impacting the aquaculture potential such as features related to growth (e.g. Vanina et al. 2019a), nutrition (e.g. [START_REF] Jonassen | Geographic variation in growth and food conversion efficiency of juvenile Atlantic halibut related to latitude[END_REF], reproduction (e.g. [START_REF] Kokita | Latitudinal compensation in female reproductive rate of a geographically widespread reef fish[END_REF]), aggressiveness (e.g. ). In such species, assessment of wild population aquaculture potential could pave the way to improve current fish stock or even restart an improved domestication process with better populations if no alternatives can be considered.

Since considering wild geographic differentiation could facilitate aquaculture diversification process, it raises the question how its integration in domestication programs should be achieved. Indeed, this integration cannot be based on very long-term or unrationalized experiments otherwise using wild geographic differentiation for domestication programs would be poorly justified. Therefore, we here propose a conceptual approach to facilitate the integration of geographic differentiation in new candidate species domestication processes.

HOW TO TAKE INTO ACCOUNT WILD GEOGRAPHIC DIFFERENTIATION: A THREE-STEP INTEGRATIVE APPROACH

The aim of this work is to propose a new standardized and rationalized three-step integrative approach to integrate wild intraspecific differentiation in new domestication programs through a multi-function and multi-trait assessment. This approach aims at facilitating domestication of new wild fish candidates or species at incipient domestication levels facing major bottlenecks in the domestication process and/or production-related issues. It aims at, successively, classifying, evaluating, and identifying best population group(s) in the context of new domestication trials (Fig. 1). Step 1 -Classification of the wild intraspecific biodiversity

Evaluating the potential for aquaculture of all wild populations of a particular species would be time/money-consuming and is, ultimately, not achievable in practice. Moreover, such comprehensive evaluation would be inaccurate because all conspecific populations are not genetically and phenotypically divergent [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Hewitt | The genetic legacy of the Quaternary ice ages[END_REF].

However, comparing randomly chosen wild populations is not an efficient solution to this issue because the best population(s) for aquaculture purpose could be missed out. An efficient rationalization relies on the development of a classification system that can identify population groups that have different/independent demographic histories and/or potential local adaptations, making divergences in aquaculture potentials likely. Therefore, such a classification should be based on proxies reflecting evolutionary histories and/or local adaptations of the different population groups. Three different proxies can be used: (i) phenotype, (ii) habitat, and (iii) genetic information.

Phenotype, especially morphological characteristics (e.g. color patterns, shape), is the earliest, the easiest, and the most commonly used information to classify biological units [START_REF] Strauss | Taxonomic Methods : Morphology[END_REF][START_REF] Haig | Taxonomic Considerations in Listing Subspecies Under the U.S. Endangered Species Act[END_REF][START_REF] Craig | Revision of the polytypic electric fish Gymnotus carapo (Gymnotiformes, Teleostei), with descriptions of seven subspecies[END_REF]. It has been widely used to define subspecies [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Haig | Taxonomic Considerations in Listing Subspecies Under the U.S. Endangered Species Act[END_REF]) which can be an efficient classification strategy to split population groups with different aquaculture potentials (e.g. for fish species, Pivnička 1970; [START_REF] Karakousis | Morphological variability among seven populations of brown trout, Salmo trutta L., in Greece[END_REF][START_REF] Kalayci | Genetic and molecular evidence that brown trout Salmo trutta belonging to the Danubian lineage are a single biological species[END_REF]. Other phenotypic information such as reproductive or behavior traits could be used but, to our knowledge, they have not been Habitat information (biotic and/or abiotic factors) has rarely been used to classify conspecific populations (but see e.g. the distinction between habitats, such as rivers or lakes, contributed to define intraspecific units in S. trutta, [START_REF] Blanc | European inland water fish : a multilingual catalogue[END_REF][START_REF] Guyomard | Chapitre 3 -Diversité génétique de la truite commune[END_REF]). Yet, one could expect that populations living in different biotic/abiotic conditions can display different demographic histories or local adaptations [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]. Therefore, a relevant approach to classify populations before evaluating their aquaculture potential could simply consist of developing a classification based on habitat differentiations (e.g. different biogeographic regions, distinct hydrographic basins, different water parameters). However, establishing if different habitats can lead to differential evolutionary paths between allopatric populations is still hard to achieve due to the potential non-congruence with population-specific histories and/or local adaptations. Moreover, there is a part of subjectivity when selecting criteria to detect habitat specificity. Therefore, these limitations make this classification approach unpractical to date for fishes.

Genetic information has been increasingly taken into account to investigate intraspecific differentiation [START_REF] Frankham | Resolving taxonomic uncertainties and defining management units[END_REF][START_REF] Miralles | The integrative future of taxonomy[END_REF]). The phylogeography-based classification appears as one of the most suitable strategies to achieve an a priori classification. Phylogeography aims at identifying groups of genetically differentiated populations which underwent specific demographic histories [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF] and could have acquired, through local adaptations, some phenotypic specificities. Moreover, information about phylogeographic structure is already available for many fish species [START_REF] Bernatchez | Comparative phylogeography of Nearctic and Paleartic fishes[END_REF][START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF]). In the context of our three-step approach, genetic proxies allow maximizing chances of detecting populations with different potentials for aquaculture that can be conserved in production environments. Indeed, domesticated fishes will often be produced in a culture environment which can be quite different from their native habitat. Therefore, only genetic-based divergences are of interest while differentiations triggered by phenotypic plasticity (i.e. the ability of a genotype to vary in phenotype depending on environmental conditions; [START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF] processes would be useless.

However, special attention should be paid to the limitations of the genetic approach. On the one hand, an approach using only few arbitrarily picked genetic pieces of evidence could result in an insufficient resolution to detect populations with different potentials for aquaculture because phenotypic or ecologic differentiations are not always being represented by many genetic differences, making their detection unlikely when using a small part of the genome [START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF][START_REF] Cruaud | Empirical assessment of RAD sequencing for interspecific phylogeny[END_REF][START_REF] Patwardhan | Molecular Markers in Phylogenetic Studies-A Review[END_REF]. This places a premium on using large genome parts or highly variable DNA sequences. On the other hand, a high resolution genetic-based classification could fail because of absence of interpopulational variation of the potential for aquaculture despite different evolutionary histories revealed by genetic markers. Using sequences of genes involved in traits impacting the potential for aquaculture could be an efficient solution. Unfortunately, such an approach remains unfeasible to date because (i) most traits are under polygenic control, (ii) the genetic basis of variation in traits is often very complex, and (iii) quantitative trait loci are mostly studied for a few major aquaculture species [START_REF] Mackay | Introduction to quantitative genetics[END_REF][START_REF] Yue | Recent advances of genome mapping and marker-assisted selection in aquaculture[END_REF][START_REF] -Abdelrahman | Aquaculture genomics, genetics and breeding in the United States: current status, challenges, and priorities for future research[END_REF][START_REF] Robledo | Applications of genotyping by sequencing in aquaculture breeding and genetics[END_REF]. Therefore, the risk of using a classification which might not lead to the identification of inter-populational divergences cannot be ruled out to date but several studies already highlighted a congruence between genetic differentiation in neutral markers and phenotypic differentiation in controlled conditions (e.g. [START_REF] Rosauer | Development of yellow perch (Perca flavescens) broodstocks: Initial characterization of growth and quality traits following grow-out of different stocks[END_REF]Vanina et al. 2019a).

Overall, special attention should be paid to the a priori classification used, and advantages/disadvantages of each proxy should be assessed for each target species through co-working with systematicians, phylogeographers, and ecologists. The resulting classification allows identifying the different prospective units (i.e. groups of allopatric populations differentiated) that will be evaluated in the step 2.

Step 2 -Evaluating keys traits of the aquaculture potential

The step 2 aims at comparing the performances of prospective units in fish farming conditions through an integrative (i.e. multi-function and multi-trait) assessment. For a wild species for which even acclimatization has not been tried before, it implies to first design a culture system that most likely will be suitable for the targeted species and stakeholders. Such a system can be defined by applying farming conditions used for phylogenetically closely related or ecologically similar fish species that are already produced in captivity or using knowledge from habitat conditions experienced by wild populations [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF]). For fish species for which incipient production already exists, the current aquaculture conditions should be used. Choosing the aquaculture system (i.e.

domestication system) in which wild populations will be assessed is an important preliminary step. Indeed, expression of traits shaping the aquaculture potential can change according to the environment (e.g. [START_REF] Rowland | Production of silver perch (Bidyanus bidyanus) fingerlings at three stocking densities in cages and tanks[END_REF]). A relevant aquaculture potential assessment should be thus obtained through bioassays in a human-controlled environment as close as possible to the targeted production system (e.g. cages, flow-through system, indoor Recirculated Aquaculture System [RAS], ponds). This means that all prospective units should be evaluated in a common-garden experiment in which the rearing system is similar to future rearing conditions. Therefore, this evaluation might have to be performed again if another rearing system is considered (i.e. the results from a RAS assessment might not be useful for pond production).

Special attention should be paid to which set of individuals is needed for the aquaculture potential assessment. Two alternative solutions can be used: (i) broodstock sampling or (ii)

early-life stage collection. One could consider that it is necessary to sample wild broodstock to produce captive-born offspring that will be evaluated. This requires respecting good rearing practices in stock constitution such as using a sufficient number of individuals in order to avoid inbreeding issues (relatively to the minimal effective size; [START_REF] Duncan | Principles of finfish broodstock management in aquaculture: control of reproduction and genetic improvement[END_REF]).

However, sampling broodstock could be difficult for some species because tolerance to transport and acclimatization varies between fish taxa depending on the life stage considered [START_REF] Berka | The transport of live fish -A review[END_REF]Omeji et al. 2017, e.g. for Perca fluviatilis, early life stages (i.e. eggs, juveniles)

remain the preferred wild biological material transported by fish farmers given the high adult mortalities subsequent to transport). This implies that the sampling material choice can be species-dependent. Therefore, for some species, early life stages could be sampled as initial biological material when accessible, but the phenotypic plasticity impact might be more substantial. Beside the choice of life stage to be sampled, it should be noted that, although the step 1 aims at defining groups with similar demographic histories and/or potential local adaptations and, thus, similar aquaculture potentials, different populations from the same prospective unit could display different performances. Indeed, temporary specific environmental disturbances affecting some populations of the same prospective units (e.g.

unusual regional food shortage, disease outbreak, or local pollution events) can impact evaluated traits (e.g. [START_REF] Scott | The effects of environmental pollutants on complex fish behavior: integrating behavioral and physiological indicators of toxicity[END_REF][START_REF] Claireaux | Effects of oil exposure and dispersant use upon environmental adaptation performance and fitness in the European sea bass, Dicentrarchus labrax[END_REF] Unfortunately, some of such tests are still unavailable (e.g. unavailability/lack of efficiency of some disease detection methods) or unfeasible at large scale. Therefore, two strategies could be used: (i) sampling the same wild populations at different years and repeating independently the step 2 and/or (ii) avoiding sampling populations occurring in areas where unusual events have been recently recorded (e.g. recent chemical pollution). Because the former strategy would increase the workload, we regard this strategy as poorly implementable and recommend the latter.

The suitability of traits chosen for the evaluation is based on the relevance of the trait (i.e.

integrative traits, important to measure and relevant regarding welfare and ethics) and its accessibility (i.e. trait measurable at large scale but not necessarily evaluated yet in routine because of the lack of proper method). A literature overview of such traits for fishes (e.g. [START_REF] Lensi | La politique de diversification de l'aquaculture en Corse. La démarche "nouvelles espèces[END_REF][START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF][START_REF] Otton | Establishment of an agribusiness model for assessing the commercial viability of new species for aquaculture[END_REF][START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] François | Considerations for the Selection and Commercialization of New or Alternate Species[END_REF]) allowed us to select a first set of traits which are overall relevant for teleosts (Table 1). This selection has been further reinforced by a survey conducted among Percids and Sturgeons producers. These two species groups were chosen since they include species with recent domestication processes and with different production outputs (see Annex S1). The ongoing production of these species allows having an overview on traits which turned out to be essential for production. We asked farmers (ongoing production of one or both species groups) in this survey to give their opinion on the different traits selected and to suggest additional relevant traits to be considered (see details and results

in Annex S1 and Fig. S1). For all traits involved in the aquaculture potential assessment, there is a performance expected by stakeholders (e.g. growth: expected high growth rate; deformity: low deformity rate). Traits chosen were classified in four categories (Table 1) corresponding to the different aspects which need to be considered when starting a new domestication process.

The first category is characterized by all biological traits measured on a group of individuals of the target prospective unit which reflect the fitness (i.e. ability to survive, grow, and reproduce) in captive conditions (Table 1). This category is common to all rearing systems (e.g. on-growing survival rate important in all production systems when on-growing is part of the production outlet). It includes traits linked to the different steps of a production cycle (reproduction, larviculture, on-growing) but also to the different biological functions (reproduction, growth, nutrition, and behavior).

The second category is characterized by all biological traits which are specifically relevant to a production system (e.g. RAS, ponds, floating cages) and/or a specific production goal (e.g. fillet, whole fish sale). It includes traits (i) involved in responses to breeding-environmentspecific stresses (e.g. antipredator behavior is relevant in ponds [START_REF] Huntingford | Aquaculture and Behavior[END_REF] while resistance to handling is important in intensive monoculture in RAS, [START_REF] Milla | Spleen immune status is affected after acute handling stress but not regulated by cortisol in Eurasian perch, Perca fluviatilis[END_REF] and (ii) related to the production target (e.g. filleting yield for the food consumption output).

Here, we consider as examples two different scenarios with a common outlet (consumption market) but different rearing systems commonly used in aquaculture: RAS and ponds (Table 1). The third category includes all biological traits linked to the interaction between the group of individuals and the environment of the rearing system, which could impact the surrounding environments (e.g. invasive potential, pathogen load, competition; Table 1). In all rearing systems, there are risks of escapees (particularly relevant in outdoor culture, yet risks cannot be ruled out in indoor aquaculture; Summerfelt and Vinci 2009). These escapees can trigger negative impacts which vary according to the identity of populations bred (i.e. local population, non-native population introduced in a species native area or in a new area out of the geographic species native range): (i) invasive risk (estimated by the invasive potential; [START_REF] Kolar | Risk assessment and screening for potentially invasive fishes[END_REF]Naylor et al. 2005), (ii) introduction of pathogens (evaluated through the pathogen load; Naylor et al. 2005), (iii) genetic introgression/homogenization or outbreeding with local wild populations (see for example [START_REF] Fraser | Mixed evidence for reduced local adaptation in wild salmon resulting from interbreeding with escaped farmed salmon: complexities in hybrid fitness[END_REF][START_REF] Bolstad | Gene flow from domesticated escapes alters the life history of wild Atlantic salmon[END_REF]Wringe et al. 2018), and (iv) competition risk between domesticated and wild populations (there is no assessment protocol available for fishes [but see for other vertebrates e.g. [START_REF] Polo-Cavia | Interspecific differences in chemosensory responses of freshwater turtles: consequences for competition between native and invasive species[END_REF]]; therefore, we ruled out this last risk from the aquaculture potential evaluation).

The last category is characterized by all biological traits relative to future major challenges and disturbances. A literature overview allows identifying four main challenges. First, there are high stakes to domesticate robust individuals. Here, we describe robustness as the ability of individuals to express their production potential in a wide range of environment changes (e.g. climatic changes, feeding shifts, disease outbreaks; based on [START_REF] Knap | Breeding robust pigs[END_REF]). This includes adaptive potential to future climate change (i.e. large-scale changes predicted related to temperature, winds, and acidification) since it will provide novel challenges [START_REF] Cochrane | Climate change implications for fisheries and aquaculture Overview of current scientific knowledge. Food and Agriculture Organization of the United Nations[END_REF], especially in outdoor aquaculture (e.g. ability to survive in aquaculture conditions despite more frequent severe weather events). Second, it is also important to consider the future invasive potential, taking into account predicted climate changes, since invasive potential is partially shaped by climatic requirements. Third, the maintenance of genetic variability during domestication has been pointed out as a major feature to promote a sustainable development of aquaculture [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF]. While stock management aiming at limiting inbreeding has been proposed, the selection of units with sufficiently high genetic variability increases chances to have individual specificities of interest for future selective breeding programs (e.g. rare genes counter-selected in the wild but presenting an advantage in rearing systems; [START_REF] Vandeputte | Quelle gestion génétique de la domestication chez les poissons?[END_REF]). Finally, one major challenge relies on the acceptance of alternative aquafeeds (i.e. less rich in fish oil and fish meal) such as plant-based feeds [START_REF] Naylor | Feeding aquaculture in an era of finite resources[END_REF]. Indeed, due to wild resources limitation, it is essential to shift towards alternative feedstuffs in order to promote sustainability of aquaculture and an inter-individual variability in the ability to adapt to vegetal-based diets was already assessed for some species (e.g. Burel 2017).

Step 3 -Identification of units with high aquaculture potential

The step 3 aims at identifying units with high aquaculture potential through the establishment of an integrative decisional framework.

According to our survey, traits are perceived differently among fish farmers and are not given the same level of importance (see in Table 1; Fig. S1). For instance, growth rate during ongrowing is globally considered as very important for both Percids and Sturgeons while group structure (i.e. structure of a group of individuals created by relationships between several individuals; Hinde 1976) is evaluated as less important for both species. In addition, the importance of traits also varies between species groups, production systems, and production goals (Fig. S1). For instance, sex ratio is considered as quite important or important by 71.4% of Sturgeon farmers but only by 14.6% of Percid farmers. Therefore, in order to identify units with high aquaculture potential, it is necessary to adjust the importance of different traits through weighting coefficients. Moreover, some traits are so important (e.g. major bottlenecks preventing the completion of the life cycle) that when a minimum threshold of their required expression is not met in a unit, this latter is regarded to be void of aquaculture potential. For instance, a paltry survival or fecundity rate observed in a unit will impede further domestication programs (e.g. inability for males to fertilize eggs due to the absence of courtship behavior in Senegalese sole [Solea senegalensis]; [START_REF] Guzmán | Vitellogenin, steroid plasma levels and spawning performance of cultured female Senegalese sole (Solea senegalensis)[END_REF][START_REF] Morais | New developments and biological insights into the farming of Solea senegalensis reinforcing its aquaculture potential[END_REF]. Nevertheless, special attention should be paid to the definition of minimum required expression threshold needed for a trait. Indeed, although some trait expressions can constitute a major bottleneck in future production, they might not fully prevent domestication/production or depress profitability (as observed in sturgeon aquaculture where the species high socio-economic value offset its low growing out potential and late sexual maturation). Moreover, some bottlenecks could be overcome through other alternatives such as technological improvements. Therefore, we advocate that minimum expression thresholds should be defined only for characteristics which are not surmountable at the time of the evaluation and completely prevent domestication/production.

The assessment of weighting coefficients (0 to 100; adapted from [START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF] similarly to breeding goals index but for which each trait is weighted according to its socioeconomic value; [START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF], as well as minimal expression thresholds, to all traits needs to be performed by a panel which includes all potential interested parties. These latter include fish farmers, scientists, environmental managers, and other socio-economic stakeholders. Since this approach targets species which are new candidates for domestication, stakeholders can take decisions using (i) literature, (ii) knowledge from ongoing domestication trials and farming experiences, and/or (iii) on extrapolations from closely related species when no rearing experience is available. The weight coefficient and minimal expression threshold attribution can be done through a consensus for each trait performed by all stakeholders (e.g. mean of the weights attributed by all stakeholders or using Quaker-based or spokescouncil models; [START_REF] Roy | Aide multicritère à la décision : méthodes et cas[END_REF][START_REF] Hartnett | Consensus-Oriented Decision-Making : the CODM model for facilitating groups to widespread agreement[END_REF]). These weighting coefficients and minimal expression thresholds need to be evaluated for each new domestication attempt since they can vary between species targeted and through time depending on stakeholders' expectations.

Besides trait weighting, it is unlikely that a prospective unit has the best performances for all criteria. It is more likely that a unit displays the best performance for a specific trait (e.g. best growth rate) but the worst for another (e.g. lowest larval survival rate). Therefore, an indicator is required in order to make a synthesis at the multi-function and multi-trait levels to identify units with high aquaculture potential. Some methods and associated scores were suggested at the interspecific level in order to identify good candidate species (e.g. method used in [START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF][START_REF] François | Considerations for the Selection and Commercialization of New or Alternate Species[END_REF]

WHAT ARE THE LIMITATIONS OF THE APPROACH?

Overall, three limitations should be stated: (i) methodological limitations, (ii) pragmatic concerns, and (iii) legal regulation context.

Methodological limitations

A first limitation can be dreaded if translocations of the targeted species happen concurrently with the evaluation by three-step approach. If they occur between the steps one and two of the approach, the classification step would be irrelevant for next steps of the approach. Moreover, if they happen after the selection of units with high potential for aquaculture, future population resampling in the wild could lead to the establishment of fish stock with specificities different from those expected according to the previous three-step assessment.

Even species that are not currently produced can undergo such a phenomenon because they can be the focus of recreational activities (e.g. angling), triggering the risk of introduction of exogenous individuals. Nevertheless, fish translocations are increasingly monitored due to international and local regulations, minimizing the potential negative impacts of this limitation.

Another limitation concerns step 2's experiment. It aims at (i) minimizing expression of aquaculture potential divergences driven by phenotypic plasticity due to specific wild environmental pressures and (ii) allowing observation of those shaped by genetic-based differentiations. Nevertheless, some observed prospective unit performances could not be genetically based and, thus, not be conserved in the next farmed generations. Indeed, even in a common-garden design, population-specific phenotypes can be consequences of past environmental pressures triggering phenotypic plasticity, including epigenetics effects [START_REF] Massicotte | General-purpose genotype or how epigenetics extend the flexibility of a genotype[END_REF][START_REF] Schlichting | Phenotypic plasticity and epigenetic marking: An assessment of evidence for genetic accomodation[END_REF] as well as transgenerational effects [START_REF] Mousseau | The adaptive significance of maternal effects[END_REF][START_REF] Youngson | Transgenerational epigenetic effects[END_REF]. Such phenomena cannot be ruled out since step 2's assessment in based on individuals which (i) parents lived in the wild at least some part of their life or (ii) lived in the wild if eggs are sampled (see step 2's sampling strategies). One solution to minimize this limitation consists in assessing performances over several generations. However, such a solution could be difficult to operationalize for taxa with long lifecycles. Indeed, multi-generations assessment and late sexual maturation species evaluation will increase the workload, the cost, and the length of the approach. However, overall, the use of a common-garden set up allows minimizing the impact of phenotypic plasticity.

Pragmatic concerns

Our approach can be seen as heavy-going. However, any domestication trials are still time and money consuming. Our approach aims to balance the complexity of multi-trait assessment over several prospective units (though the step 1's classification allows restricting the range of possibilities regarding biological units to compare) by choosing the best part of the wild biodiversity. Indeed, gains of highlighting populations with the highest aquaculture potential can provide important benefits for fish production (see for instance for Perca fluviatilis, [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]Toomey et al. 2019;Vanina et al. 2019a). However, consequent investment may not be operated for each new candidate. One way to decrease investments could consist of extrapolating the knowledge or the results obtained for some species to others in order to minimize the extent of evaluation for new species. Especially, population classification of a species (step 1 when based on genetic differentiation) could be inferred from commonly observed phylogeographic patterns of other co-distributed taxa (e.g. rather than based on a new genetic assessment across the species range (e.g. Danubian regions often host fish populations with genetic specificities and therefore could be considered as a relevant place for step 2's sampling). Indeed, an overview of already known phylogeographic structures (e.g. [START_REF] Bernatchez | Comparative phylogeography of Nearctic and Paleartic fishes[END_REF][START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF][START_REF] Hickerson | Phylogeography's past, present, and future: 10 years after Avise[END_REF]) allows identifying general phylogeographic patterns in fishes. This means that one could assume that population(s) from a region could be genetically distinct since populations of other taxa display genetic specificities. Therefore, such populations should be evaluated in the step 2.

Legal regulation context

One limitation could be related to national and international regulations regarding the biological material sampling or importation. Indeed, such regulations should be considered before step 2 since it would be a waste of time and energy to perform an assessment on wild populations that could not be imported or sampled to create fish stocks for future production.

WHEN IS THIS APPROACH APPLICABLE?

The three-step approach is designed to help stakeholders to facilitate domestication programs of new species or species at incipient domestication levels (i.e. from level one to three of the domestication process; Teletchea and Fontaine 2014). At these levels, domestication programs are commonly facing major bottlenecks in domestication and/or production (e.g.

Anguilla anguilla; Tomkiewicz et al. 2012). Focusing domestication efforts on the units with the highest aquaculture potential could allow overcoming or minimizing such bottlenecks.

Moreover, the approach allows considering all traits important for aquaculture (i.e. multi-trait assessment) from the outset of the domestication programs and thus most likely facilitating future production development.

One could expect that the three-step approach is a less efficient alternative than selective breeding methods that allow improving fish stocks at individual/family levels [START_REF] Lind | Selective breeding in fish and conservation of genetic resources for aquaculture[END_REF]). However, selective breeding methods are poorly implementable when only a part of the lifecycle is performed in captivity (i.e. capture-based productions) or when significant number of wild individuals must still be integrated in farmed fish stocks. Under these circumstances corresponding to the early levels of domestication, the three-step approach can be seen as a way to move forward in the domestication process and to design the best fish stocks before potentially handing over to selective breeding programs in the further levels of domestication (i.e. levels four and five). Therefore, the three-step integrative approach and selective breeding methods should be seen as complementary rather than opposite and could eventually be used successively along the domestication process. We argue that selective breeding programs should be favored at intermediate stages of domestication (i.e. level four) when the differentiation within population is higher than the inter-populational differentiation [START_REF] Quillet | Variabilité génétique de la réponse aux organismes pathogènes : un outil pour améliorer la santé des mollusques et poissons d'élevage[END_REF] or when the genetic gain prediction for one generation of individual selection is higher or equal to the between-population differentiation [START_REF] Vandeputte | Multi-site evaluation of the rearing performances of 5 wild populations of European sea bass (Dicentrarchus labrax)[END_REF].

Nevertheless, future studies are needed to assess to feasibility of the three-step approach in the real world production by evaluating costs, gains, and human and technological means. More specifically, cost and benefit comparison with selective breeding programs are needed to assess the complementarity of the two approaches and the relevance of the three-step method.

However, cost and benefit analyses are performed for selective breeding programs (e.g. [START_REF] Janssen | Cost-benefit analysis of aquaculture breeding programs[END_REF]), but they are not available for the three-step approach since we propose here a new methodology which remains to be tested.

The three-step integrative approach aims to be a model approach applicable to all new candidate species, including non-fish taxa (e.g. for shrimp stripes, Wenger 2012; U.S. Fish and Wildlife Service 2017) provided that the set of traits is adjusted for the target taxon group (e.g. swim bladder inflation or cannibalism rates are not relevant for molluscs while success of successive metamorphoses are). However, as stated previously, the trait choice must also be adjusted according to (i) production goals, (ii) production method, and (iii) technologic advances. First, the approach can be applied to restocking or ornamental market provided that further relevant traits are integrated in category two. For instance, in the case of ornamental aquaculture, external color needs to be considered while resistance to wild pathogens are particularly relevant for restocking programs. Second, the approach adjustment is also necessary when considering some production methods such as polyculture for which traits related to interspecific interactions should be considered. Third, the trait list can also be updated through time as technologic development and new challenges arise (e.g. sperm longterm storage techniques would allow to improve fertilization issues, making fertilization rate less important for the aquaculture potential score; e.g. [START_REF] Alavi | Sperm Morphology, Physiology, Motility, and Cryopreservation in Percidae[END_REF]Policar et al. 2019).

WHAT'S NEXT?

Once the multi-stage aquaculture potential assessment approach is performed, questions can be raised when planning future production. An overview of previous studies which used wild intraspecific differentiation at advanced stages of domestication, show that two alternative paradigms to exploit geographic differentiation can be considered [START_REF] Gjedrem | Improvement of productivity through breeding schemes[END_REF](Gjedrem , 2005a): (i) crossing the best prospective units (i.e. crossbreeding) or (ii) concentrating on the best unit to develop production (i.e. purebreeding). On the one hand, crossbreeding aims at exploiting hybrid vigor, or heterosis, which is characterized by offspring performing better than parents for one or several traits. This strategy was explored for several species such O. niloticus [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF] or the rainbow trout (Oncorhynchus mykiss; [START_REF] Ayles | Genetic differences in growth and survival between strains and hybrids of rainbow trout (Salmo gairdneri) stocked in aquaculture lakes in the Canadian prairies[END_REF]). However, no heterosis effect was found for some species when crossing several wild populations such as S. salar [START_REF] Gjerde | Complete diallel cross between five strains of Atlantic salmon[END_REF]. This strategy appears as interesting (i) when the aquaculture potential is not that different between prospective units and if an heterosis effect is demonstrated or (ii) when planning selective breeding programs to ensure a large genetic basis. On the other hand, purebreeding, implying a continuous genetic improvement within a biological unit(s) over a long period of time, was also widely used in terrestrial livestock species as well as for fishes [START_REF] Gjedrem | Genetic origin of Norwegian farmed Atlantic salmon[END_REF][START_REF] Gjedrem | Selective Breeding in Aquaculture: An Introduction[END_REF][START_REF] Gjedrem | The first family-based breeding program in aquaculture[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. This strategy has been pointed out as particularly efficient when one biological unit presents overall better performances than other units [START_REF] Gjedrem | Improvement of productivity through breeding schemes[END_REF](Gjedrem , 2005a)). Indeed, purebreeding has been recommended in breeding programs when there is additive genetic variation while crossbreeding has been suggested if the magnitude of hybrid vigor is larger than the expected genetic gain though a purebreeding program [START_REF] Gjedrem | Improvement of productivity through breeding schemes[END_REF](Gjedrem , 2005a)).Whether or not crossing prospective units depends on breeding goals and genetic variation of traits of interest and is beyond the three-step integrative approach which is the first step before potential future breeding programs.

ACKNOWLEDGMENTS

We are grateful to the European Percid Fish Culture (EPFC) group, the Syndicat Français de l'Aquaculture Marine et Nouvelle (SFAMN) and all fish farmers which contributed to the survey led in this work. LT is supported by a grant from the French Ministère de l'Enseignement Supérieur et de la Recherche. This work was supported by the region Grand Est (DomPop project).

APPENDICES Annex S1: Context of the survey

The survey focused on two different scenarios targeting species at the beginning of the domestication process and with a high socio-economic interest. The first scenario focused on European production of Percids, taking as an example the European Perch (Perca fluviatilis) and the pikeperch (Sander lucioperca). These two species are among the most promising species to boost European inland aquaculture [START_REF] Fontaine | L'élevage de la perche commune, une voie de diversification pour l'aquaculture continentale[END_REF][START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF]Kestemont et al. 2015a) due to their high socio-economic interest (high market value and recreational interest; [START_REF] Kestemont | Chap. 11 -Aquaculture[END_REF]Kestemont et al. 2015a). They are at their nascent stage of production and geographic differentiation has already been demonstrated for European perch (e.g. [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]Toomey et al. 2019). Percids farming still presents several bottlenecks related for instance to high growth heterogeneity and subsequent cannibalism, low survival rate, or low egg quality (Kestemont et al. 2015a). Therefore, there is a strong interest in improving these species' productions. The second scenario consisted in investigating Sturgeons production (Acipenser ruthenus, Acipenser gueldenstaedtii, Acipenser stellatus, Acipenser baerii, Acipenser persicus, Hybrid bester, and Huso huso) for consumption in Europe. Substantial progress in rearing techniques in the 1980s allowed developing a fruitful sector for meat and caviar production [START_REF] Bronzi | A brief overview on the status and prospects of sturgeon farming in Western and Central Europe[END_REF][START_REF] Williot | L'élevage de l'esturgeon sibérien (Acipenser baerii Brandt) en France[END_REF]. The market will most likely extend [START_REF] Williot | L'élevage de l'esturgeon sibérien (Acipenser baerii Brandt) en France[END_REF], triggering an interest in improving Sturgeon domestication processes. This survey being focused on biological traits, stakeholders involved in the environmental and economic sectors were not consulted in this preliminary investigation.

The survey was led between February and March 2019. For Percids, between nine and 12 answers were taken into account (variable numbers depending on production goals and production systems of the different farms; e.g. no answers for the larval period when larviculture is not performed in the farm, see Fig. S1 for details), except for anti-predatory behavior for which only three answers were considered since only three farms used outdoor systems. Most of the fish farms use indoor RAS (91.6% [n=11 farms]), 25.0% [n=3 fish farms] use outdoor RAS, and two fish farmers use both systems. The fish farms produce fillets (75%, n=9 fish farms), fingerlings (75%, n=9 farms), and/or wholefish for consumption (33.33% of the farms, n=4 fish farms). Nine farms have more than one production goal.

Concerning Sturgeons, between five and eight answers were considered for each trait depending on production goals and rearing systems of the different fish farms (see Fig. S1 for details). Most of the fish farmers use several rearing systems, including flow-through systems (75% n=6 fish farms), 50% using indoor RAS (n=4), 25% using outdoor RAS (n=4), and 25% using ponds (n=2). Regarding production goals, fish farms produce caviar (75%, n=6), juveniles (37.5%, n=3), fillets (50%, n=4), individuals for restocking (12.5%, n=1), and/or wholefish for consumption (62.5%, n=5). One farm produces Percids and Sturgeons. period, on-growing period, traits relative to category 2 [i.e. biological traits which relevance vary according to production systems and production goals], and traits linked to current and future challenges (categories 3 [i.e. biological traits linked to the interaction between the group of individuals and the rearing system, which could impact surrounding environments] and 4 [i.e. biological traits relative to future major challenges and disturbances]). Colors correspond to the different degrees of importance: (i) light grey when the trait was not considered as relevant (even though part of the production goal), (ii) dark grey when the fish farmer has no opinion on the importance, (iii) red when the trait was estimated as negligible, (iv) yellow when the trait was considered as important, and (v) green when the trait was considered as quite important. The number above each trait bar indicates the number of farmers which gave their opinion on this particular trait. This chapter corresponds to the first step of the integrative method: the establishment of an intraspecific classification to identify prospective units (i.e. groups of conspecific and allopatric populations which are differentiated). As a first approach, we chose to perform a phylogeographic study. Indeed, population groups having different/independent demographic histories and/or potential local adaptations are likely to present divergences in key traits.

Therefore, we used genetic differentiation in neutral markers (i.e. not submitted to selection and not influencing fitness) as a proxy to highlight population groups with potential divergences in key traits. We had already shown in a study, performed in collaboration with some Czech colleagues from the University of South Bohemia, a link between genetic differentiation and a few key trait differentiations for three European perch populations (Vanina et al. 2019a).

This chapter aimed at establishing an intraspecific classification but also aimed at considering the use of this classification for conservation purposes. Indeed, when the production and subsequent trade begin, translocations of individuals within and outside the species range lead to many conservation concerns such as outbreeding, genetic homogenization, or competition risks threatening the wild population(s) of produced/managed species. Although these challenges and issues have been reported many times (i.e. in vertebrates and invertebrates, in aquatic and terrestrial taxa), species conservation concerns and translocation regulations often begin to be considered when issues are observed. Indeed, lessons from the past are poorly taken into account when a species is becoming of interest for humans although they should be considered to avoid common issues. One way to overcome these challenges consists of integrating the knowledge of spatial genetic variability patterns in conservation and management strategies of species.

In this chapter, we proposed to consider intraspecific genetic variability for the ongoing development of Perca fluviatilis production. The aquaculture of this fish species is still at the nascent stage. Therefore, it is a good opportunity to provide (i) guidelines for conservation and efficient regulations of the movements of the species within its natural range and (ii) a genetically-based population structure which is the first step before the bioassays (i.e. step two of the integrative approach).

INTRODUCTION

During the Quaternary, most inland species went through several climatic cycles [START_REF] Andersen | The ice age world: An introduction to quaternary history and research with emphasis on North america and northern europe during the last 2.5 million[END_REF]. The alternation of Ice Ages and interglacial periods resulted in range shifts which depended on eco-climatic requirements and tolerances of taxa. Temperate-adapted taxa underwent range shrinking during Ice Ages and distribution expansions to at least portions of their initial distribution range during interglacial periods [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]Hewitt 2004a;[START_REF] Stewart | Refugia revisited: individualistic responses of species in space and time[END_REF], while cold-adapted taxa went through the opposite pattern [START_REF] Fedorov | Comparative phylogeography and demographic history of the wood lemming (Myopus schisticolor): implications for late Quaternary history of the taiga species in Eurasia[END_REF][START_REF] Magnuson | Temperature as an Ecological Resource[END_REF][START_REF] Martinet | Following the cold: geographical differentiation between interglacial refugia and speciation in the arcto-alpine species complex Bombus monticola (Hymenoptera: Apidae)[END_REF][START_REF] Quinzin | Glacial survival of trophically linked boreal species in northern Europe[END_REF]. Such movements have shaped the current distribution and genetic variability patterns of species (Hewitt, 2004b;[START_REF] Stewart | Refugia revisited: individualistic responses of species in space and time[END_REF]. First, the distribution of many species was fragmented into different isolated refugia during range shrinking times [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]Hewitt 2004b). This led to a decrease of gene flow between populations and, potentially, to geographic genetic differentiations [START_REF] Hewitt | The genetic legacy of the Quaternary ice ages[END_REF][START_REF] Stewart | Refugia revisited: individualistic responses of species in space and time[END_REF]. Second, post-glacial re-colonizations of non-refuge areas led to a loss of genetic diversity through founder events occurring at the expanding front while ancestral genetic diversity was often maintained in refuge regions [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]Hewitt 2004b). well as to mitigate its potential negative impacts on wild populations [START_REF] Danancher | Genetic population structure in flatfishes and potential impact of aquaculture and stock enhancement on wild populations in Europe[END_REF].

For animal producers, understanding spatial patterns of genetic variability is potentially valuable in order to optimize the exploitation of a particular species in controlled conditions.

Indeed, genetically differentiated populations underwent specific evolutionary histories and could have acquired phenotypic specificities (i.e. geographic differentiation; [START_REF] Blanck | Large-scale intraspecific variation in life-history traits of European freshwater fish[END_REF][START_REF] Forschler | Geographical differentiation, acoustic adaptation and species boundaries in mainland citril finches and insular Corsican finches, superspecies Carduelis [citrinella][END_REF][START_REF] Youngson | Management of salmonid fisheries in the British Isles: towards a practical approach based on population genetics[END_REF]) through genetic adaptations to local environments [START_REF] Losos | Adaptation and diversification on islands[END_REF]. Some of these specificities (i.e.

characteristics which are particular to a specific population) can concern biological traits of interest for production, trade, and profit (e.g. improved provision of ecosystem services, higher resilience, higher acceptability by stakeholders; [START_REF] Imsland | The interrelation of growth and disease resistance of different populations of juvenile Atlantic halibut (Hippoglossus hippoglossus L.)[END_REF][START_REF] Janhunen | Morphological variability among three geographically distinct Arctic charr (Salvelinus alpinus L.) populations reared in a common hatchery environment[END_REF]Lecocq et al. 2016aLecocq et al. , 2016b;;[START_REF] Stort | Genetic study of aggressiveness of two subspecies of Apis Mellifera in Brazil 1. Some tests to measure aggressiveness[END_REF]. This leads to different potentials between populations for production. Ultimately, considering these population potentials can foster successful animal production development (e.g. [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF].

Globalization of species production and trade (for agriculture, pets, model organisms for scientific purposes, game, restocking, or biological control agents) leads to translocations that can threaten local species and population(s). While risks related to invasions of non-native species have been widely studied [START_REF] Mooney | The evolutionary impact of invasive species[END_REF][START_REF] Simberloff | Impacts of biological invasions: what's what and the way forward[END_REF], translocations within the distribution range of a particular species have received far less attention (Lecocq et al. 2016a). Yet, they have been shown in some cases to be more detrimental [START_REF] Buoro | Global Salmonidae introductions reveal stronger ecological effects of changing intraspecific compared to interspecific diversity[END_REF]). Translocations of genetically differentiated individuals within a species range can lead to outbreeding, genetic homogenization, or competition issues threatening genetic intraspecific variability [START_REF] Champagnon | Conspecifics can be aliens too: A review of effects of restocking practices in vertebrates[END_REF][START_REF] Cross | Genetic implications of translocation and stocking of fish species, with particular reference to Western Australia[END_REF][START_REF] Danancher | Genetic population structure in flatfishes and potential impact of aquaculture and stock enhancement on wild populations in Europe[END_REF][START_REF] Rhymer | Extinction by hybridization and introgression[END_REF]. This genetic variability (i.e. the combination of local genetic diversity and inter-population genetic differentiation) is seen as one of the key factors to species conservation and survival [START_REF] Booy | Genetic diversity and the survival of populations[END_REF][START_REF] Frankham | Introduction to Conservation Genetics[END_REF]. Indeed, local genetic diversity and inter-populational genetic differentiation contribute to the species ability to adapt to future challenges [START_REF] Laikre | Genetic population structure of fishes: Implications for coastal zone management[END_REF][START_REF] Sgrò | Building evolutionary resilience for conserving biodiversity under climate change[END_REF] and to global biodiversity that maximizes species long-term survival chances [START_REF] Conner | A primer of ecological genetics[END_REF]Lecocq et al. 2015;[START_REF] Phillimore | Are subspecies useful in evolutionary and conservation biology?[END_REF], respectively. Therefore, preserving genetic variability is an important focus in conservation programs [START_REF] Laikre | Genetic population structure of fishes: Implications for coastal zone management[END_REF][START_REF] Mankiewicz-Boczek | Genetic diversity of perch populations in three lowland reservoirs (Central Poland): Perspective for fish sustainable management[END_REF][START_REF] Sgrò | Building evolutionary resilience for conserving biodiversity under climate change[END_REF]. Given the important advantages of many produced/traded species for human livelihood, health, or economy, a complete interdiction of translocations is not feasible. Therefore, pragmatic translocation regulations are needed.

Finding spatial patterns of genetic variability allows developing relevant regulations to preserve population specificities and guidelines for translocations (e.g. Lecocq et al. 2016aLecocq et al. , 2015)).

Despite their potentially valuable integration in incipient species domestication and trade, intraspecific genetic variability patterns often begin to be considered long after the beginning of production [START_REF] Fleming | Lifetime success and interactions of farm salmon invading a native population[END_REF]Lecocq et al. 2016a;[START_REF] Lemer | Translocation of wild populations: conservation implications for the genetic diversity of the black-lipped pearl oyster Pinctada margaritifera[END_REF]. Indeed, new candidate species often start to be produced without due consideration to issues already encountered with other fish species when spatial patterns of intraspecific variability when not considered early in the domestication process [START_REF] Fleming | Lifetime success and interactions of farm salmon invading a native population[END_REF][START_REF] Lemer | Translocation of wild populations: conservation implications for the genetic diversity of the black-lipped pearl oyster Pinctada margaritifera[END_REF][START_REF] Mazur | Effect of handling and stocking density on hematocrit, plasma cortisol, and survival in wild and hatchery-reared chinook salmon (Oncorhynchus tshawytscha)[END_REF]. In this study, we focus our attention on the European perch (Perca fluviatilis L.), an inland fish species at a nascent stage of its aquaculture production. Perca fluviatilis is a temperate freshwater and brackish water fish species distributed across the Palaearctic realm (except in most of the Mediterranean Sea coast regions; [START_REF] Stepien | Taxonomy, Distribution, and Evolution of the Percidae[END_REF]. This species, traditionally used in both commercial and recreational fisheries, is the focus of an increasing interest in aquaculture since the 90s in western Europe [START_REF] Fontaine | L'élevage de la perche commune, une voie de diversification pour l'aquaculture continentale[END_REF]Kestemont et al. 2015a;[START_REF] Kestemont | Chap. 11 -Aquaculture[END_REF]. Although several major bottlenecks are still observed in aquaculture (Kestemont et al. 2015a;Policar et al. 2019), further development of P. fluviatilis production can be expected because this species has an increasingly impressive market potential (i.e. current production is largely inferior to European demand; Kestemont et al. 2015a). Since the species displays a significant invasive potential (Kestemont et al. 2015a) as well as documented intraspecific genetic (e.g. [START_REF] Bergek | Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)[END_REF][START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]) and phenotypic [START_REF] Blanck | Large-scale intraspecific variation in life-history traits of European freshwater fish[END_REF][START_REF] Pimakhin | Color variability of Eurasian perch (Perca fluviatilis): a review[END_REF][START_REF] Roch | Genetically distinct color morphs of European perch Perca fluviatilis in Lake Constance differ in susceptibility to macroparasites[END_REF]) differentiations, it is likely that (i) production potential may vary between populations and (ii) unregulated translocations could lead to dramatic consequences. This suggests that production and translocations of the European perch should be optimized and regulated, respectively, at the nascent stage of its production.

The demographic history of the European perch was investigated in previous studies.

However, most of these studies focused on limited geographic areas (e.g. [START_REF] Bergek | Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)[END_REF][START_REF] Butkauskas | Investigations into genetic diversity of the perch inhabiting Ignalina nuclear power plant cooler and other inland water bodies of Lithuania on the basis of mtDNA analysis[END_REF]. Only one study investigated the species genetic variability at large geographic scale and identified four genetic groups and three refugia (suggesting a plausible fourth one, not contributing to re-colonization) during the last glacial maximum (25,000 to 15,000 before present; [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]). However, tremendous developments in analytical and statistical approaches occurred since these previous publications. The former large-scale phylogeographic study [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]) was only based on a small part of the mitochondrial genome as well as a few Random Amplification of Polymorphic DNA (RAPD) markers but limitations of such approaches have now been highlighted. First, phylogeographic and population genetic studies based on only a small part of genome, in this case mitochondrial genome, remain controversial because (i) the part of genome analyzed is often chosen arbitrarily [START_REF] Cruaud | Empirical assessment of RAD sequencing for interspecific phylogeny[END_REF]) and (ii) population differentiations are not always characterized by the accumulation of many genetic differences, making their detection by using small genome part unlikely [START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF][START_REF] Patwardhan | Molecular Markers in Phylogenetic Studies-A Review[END_REF]. Second, multilocus nuclear markers such as RAPD markers have been replaced

by more powerful multi-allelic markers such as microsatellites because RAPD approach presents a low reproducibility and a limited usefulness for meta-analysis [START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF][START_REF] Sunnucks | Efficient genetic markers for population[END_REF]. Beside potential limitations due to the state of scientific and technical knowledge at the time of previous investigations, an overview of phylogeographic studies investigating specific geographic areas shows discrepancies in conclusions (see for instance [START_REF] Gyllensten | Monomorphism of allozymes in perch (Perca fluviatilis L.)[END_REF][START_REF] Olsson | Genetic population structure of perch Perca fluviatilis along the Swedish coast of the Baltic Sea[END_REF]. Therefore, due to analytical limitations and discrepancies between conclusions, previous studies have not demonstrated conclusively the spatial distribution of genetic variability in P. fluviatilis.

In the present study, we establish the spatial genetic variability patterns and the population structure of the European perch through the analysis of four mitochondrial regions and eight nuclear microsatellite markers. By considering these spatial patterns, we aim to provide (i) a genetically-based population structure that could act as an impetus for further improvement of P. fluviatilis production and (ii) guidelines for efficient regulations of the species translocations within its natural range to preserve wild intraspecific variability.

MATERIAL AND METHODS

Sampling

We collected 409 European perch tissue samples from 84 sampling sites (five individuals per sampling site, except for six sites for which less individuals were collected) from different drainage basins (estuaries, rivers, and lakes) across the species native range in western Eurasia and Siberia (Table S1, Fig. 1, and Fig. S1). Sample providers dissected a small piece of caudal or dorsal fins or scales from field captured individuals. Samples were stored in 99% ethanol at -20 °C. We included samples of P. schrenkii Kessler 1874 (seven samples from two sites, Table S1) and P. flavescens Mitchill 1814 (sequences from GenBank), the two sister species of P. fluviatilis, as outgroups for mitochondrial analyses. All samples were collected respecting both European and national sampling regulations. We isolated genomic DNA using DNeasy® Blood and Tissue kit (QIAGEN France SAS®) (18-h incubation in proteinase K at 56 °C). Voucher specimens used in molecular investigations were deposited at the University of Lorraine (Nancy, France).

Genetic analyses

We fluviatilis origin of each sequence was checked in NCBI using BLAST [START_REF] Zhang | A greedy algorithm for aligning DNA sequences[END_REF].

We aligned all sequences using MAFFT (default parameters; [START_REF] Katoh | MAFFT online service: multiple sequence alignment, interactive sequence choice and visualization[END_REF]). Translation to proteins for partial COI and Cytb sequences was performed in Mesquite using vertebrate mitochondrial code. We deposited sequences in GenBank (GenBank accession numbers:

MG969725 to MG969793; Table S1). Mitochondrial regions were ultimately concatenated into a single alignment for the different analyses using Mesquite 3.20 [START_REF] Maddison | Mesquite: a modular system for evolutionary analysis. Magnhagen C (2006) Risk-taking behavior in foraging young-of-the-year perch varies with population size structure[END_REF]. CHAPTER 3 122

Spatial distribution of genetic variability

Analyses hereby presented were performed on the concatenated mitochondrial alignment (but see Table S2 and Fig S2 for locus specific results). We calculated haplotype diversities and nucleotide diversities [START_REF] Nei | Mathematical model for studying genetic variation in terms of restriction endonucleases[END_REF] in DnaSP [START_REF] Librado | DnaSP v5: a software for comprehensive analysis of DNA polymorphism data[END_REF]. We constructed haplotype networks using the median-joining algorithm [START_REF] Bandelt | Median-joining networks for inferring intraspecific phylogenies[END_REF] S3. We conducted BA in MrBayes 3.1.2 [START_REF] Ronquist | MrBayes 3: Bayesian phylogenetic inference under mixed models[END_REF]. Selected models unimplemented in MrBayes were replaced by the closest overparameterized model available [START_REF] Huelsenbeck | Frequentist properties of bayesian posterior probabilities of phylogenetic trees under simple and complex substitution models[END_REF]. All analyses were performed on concatenated and individual markers. We ran five independent analyses in MrBayes (20 million generations)

and the first 380,000 generations were discarded as burn-in. We performed ML analyses in Garli 2.0 [START_REF] Zwickl | Genetic algorithm approaches for the phylogenetic analysis of large biological sequence datasets under the maximum likelihood criterion[END_REF]. We carried out five independent runs and evaluated statistical confidence in nodes using 1,000 non-parametric bootstrap replicates.

In addition, we generated maps displaying the geographic distribution of local genetic diversity. For this purpose, we first used a sliding window approach to estimate the nucleotide diversity π [START_REF] Nei | Mathematical model for studying genetic variation in terms of restriction endonucleases[END_REF]) associated with each cell of a template raster grid covering the study area (spatial resolution: 12.5 arcmin). This method attributes, to each grid cell, a value of nucleotide diversity estimated from sequences sampled within a circle centered on the considered cell. Nucleotide diversity is corrected for unequal sample size and is based on both allelic frequencies and genetic distances between sequences, which are complementary aspects when studying distribution of genetic variability. The sliding window is implemented in a R script available with the toolbox SPADS [START_REF] Dellicour | SPADS 1.0: a toolbox to perform spatial analyses on DNA sequence data sets[END_REF]. We tested several values for the radius r (25, 50, 100, and 200 km) used to define the sliding window.

Several radius values were tested in order to evaluate the impact of the sliding window extent on the genetic diversity distribution. Starting from the raster files obtained by the sliding window approach, we then performed an inverse distance interpolation with the R function "GDivPAL" also available with the toolbox SPADS (distance weighting parameter a = 5). As CHAPTER 3 123 a third step, we drew a convex hull around fictive circles of 100 km radius centered on sampling locations for each generated interpolation surface in order to define the different "study areas" by cropping the surfaces and thus avoiding excessive extrapolation. Only results with a radius of 50 km are presented and maps with other radius are available in Fig. S3. The use of the sliding window approach allows to avoid the arbitrary "population" delimitation and to minimize the effect of small sampling sizes [START_REF] Lecocq | Divergent geographic patterns of genetic diversity among wild bees: Conservation implications[END_REF]. Indeed, through this approach, the genetic diversity is estimated within a circle radius. For a particular location, the genetic diversity can thus be estimated from a large number of individuals even though few individuals were sampled per site (except in the case of isolated sampling sites).

For the microsatellite dataset, potential errors (allelic dropouts, stuttering, and null alleles) were assessed using the MICRO-CHECKER software [START_REF] Van Oosterhout | MICROCHECKER: software for identifying and correcting genotyping errors in microsatellite data[END_REF]).

We conducted a factorial correspondence analysis (FCA) as implemented in the program GENETIX 4.02 [START_REF] Belkhir | GENETIX 4.05, logiciel sous Windows TM pour la génétique des populations[END_REF]) in order to get a graphical representation of genetic variation among individuals. We estimated global locus genetic diversity through the computation of two coefficients in HP-RARE 1.1 program [START_REF] Kalinowski | hp-rare 1.0: a computer program for performing rarefaction on measures of allelic richness[END_REF]): number of alleles per locus (A) and allelic richness (Ar). Number of private alleles was assessed in GenAIEx 6.5 [START_REF] Peakall | GenAIEx 6: genetic analysis in Excel. Population genetic software for teaching and research[END_REF] and observed (Ho) and expected (He) heterozygosities were calculated in GENETIX. As for the analysis of mitochondrial sequences, we generated a map representing the geographic distribution of genetic variability.

For this purpose, we estimated and averaged the Bray-Curtis dissimilarity [START_REF] Bray | An ordination of the upland forest communities of Southern wisconsin[END_REF] within a sliding window using the same interpolation protocol detailed above for mitochondrial sequences.

Population structure

For mitochondrial sequences, we first assessed population structure by estimating Φ ST statistic on sampling sites through an Analysis of MOlecular VAriance (AMOVA; i.e. when considering only one group of sampling sites; [START_REF] Excoffier | Analysis of molecular variance inferred from metric distances among DNA haplotypes: Application to human mitochondrial DNA restriction data[END_REF]) performed in Arlequin 3.5 (Excoffier and Lischer 2010) with 10,000 permutations. We then used SPADS to estimate the phylogeographic structure as measured by N ST -G ST [START_REF] Pons | Measuring and testing genetic differentiation with ordered versus unordered alleles[END_REF], and its statistical significance was tested by recalculating them with 10,000 random permutations of haplotypes in the original data sets. As the global Φ ST estimate was significant, patterns of genetic variation were assessed by Spatial Analysis of MOlecular VAriance (SAMOVA; K=2 to K=10; 10,000 iterations, ten repetitions; [START_REF] Dupanloup | A simulated annealing approach to define the genetic structure of populations[END_REF] as implemented in SPADS.

The SAMOVA algorithm assigns sampling sites to groups (or "clusters") based on geographic vicinity and sequence similarity. The number of clusters reflecting the most-likely genetic structure was chosen based on the maximized among-group variation (Φ CT ). Among the ten repetitions performed for a given K (number of clusters) to identify, we systematically kept the run associated with the highest value of Φ CT .

For microsatellites data, we first assessed global differentiation by estimating F ST statistic on sampling sites (i.e. when considering only one group of sampling sites) through an AMOVA performed in Arlequin 3.5 (Excoffier and Lischer 2010) with 10,000 permutations. Genetic population structure was assessed with the Bayesian clustering method implemented in STRUCTURE 2.3.4 [START_REF] Pritchard | Inference of population structure using multilocus genotype data[END_REF]) that aims to identify population clusters respecting

Hardy-Weinberg and linkage equilibriums. We performed ten independent STRUCTURE runs for each tested value of K ranging from one to 50. Each run was made of 10 million Markov chain Monte Carlo iterations, discarding the first one million iterations as burn-in. We used the model with correlated allele frequencies and assuming admixture. The most probable K was identified based on the consensus of the ΔK method [START_REF] Evanno | Detecting the number of clusters of individuals using the software STRUCTURE: A simulation study[END_REF]) and of loglikelihood values associated with each K ("log(P(K)) method") using STRUCTURE HARVESTER 0.9.94 [START_REF] Earl | STRUCTURE HARVESTER: a website and program for visualizing STRUCTURE output and implementing the Evanno method[END_REF]. We conducted another analysis with the most probable K using the software CLUMPP 1.1.2 [START_REF] Jakobsson | CLUMPP: a cluster matching and permutation program for dealing with label switching and multimodality in analysis of population structure[END_REF] to calculate individual ancestry values (one Q-value per cluster) averaged over ten runs using the "Greedy" algorithm.

RESULTS

Sequence and microsatellite variation

The concatenated mitochondrial alignment resulted in 1,893 aligned nucleotides: 541 base pairs (bp) from 16S (10 variable sites), 641 bp from COI (23 variable sites), 399 bp from Cytb (18 variable sites), and 312 bp from D-Loop (seven variable sites; see descriptive indicators in Table S2). Our median-joining network results showed a star-like structure with one dominating haplotype surrounded by several haplotypes (distant from the main haplotype by one or two mutations) as well as other less frequent haplotypes (Fig. 2A). For the microsatellite dataset based on eight markers, there was no significant evidence for the presence of scoring errors across populations. Number of alleles varied from 14 (Yp111) to 40 (Svi17) between loci across samples and descriptive indicators are available in Table S4.

CHAPTER 3 125

Geographic distribution of genetic variability

Overall, our median-joining network (64 different haplotypes) based on mitochondrial concatenated alignment supported the geographic genetic differentiation between five major groups of haplotypes (Fig. 2A): (i) the current European Plain (i.e. ranges from the Pyrenees Mountains across northern Europe to the Ural Mountains in Russia), (ii) the Danube drainage system and Alpine Foreland (i.e. from Lake Constance in the west to Linz in the east), (iii) the Balkans, (iv) western and northern Fennoscandia, and (v) eastern Europe (i.e. between 20°E and 40°E and between 45°N and 70°N). ML and BA phylogenetic analyses led to similar tree topologies, thus here we present only results obtained with the concatenated matrix with Bayesian analyses. The overall geographic pattern for each marker is similar to network analyses, except for the delineation between western and northern Fennoscandia and eastern Europe (Fig. S4). However, there was no lineage sorting within P. fluviatilis and intraspecific lineages were not well supported (Fig. S4). Nonetheless, with all markers and different analyses, Danube individuals formed a monophyletic group. Regarding microsatellites, the FCA showed that Balkans, Danube and Alpine Foreland tended to be slightly separated from other sampling sites (Fig. S5).

Mapping of local genetic diversity based on mitochondrial sequences and microsatellites

showed that this genetic diversity was unevenly distributed (Fig. 2B-C). The mitochondrial nucleotide diversity was higher in Fennoscandia, surrounding the Danube and along an eastern diagonal (i.e. from Baltic countries to the north of the Black Sea; Fig. 2B). On the contrary, lower diversity was highlighted in western Europe. Genetic diversity estimated with microsatellites was quite homogeneous across the sampling range with lower genetic diversity spots in western and central Europe as well as in southern and northern Finland (Fig. 2C).

Population structure

Geographic structuring was significantly supported by analysis of AMOVA which indicated a differentiation over all sampling sites (Φ ST = 0.58, p-value < 0.05). We also found a significant phylogeographic signal (N ST -G ST = 0.14, p-value < 0.05). In SAMOVA, Φ CT decreased until K = 6 clusters before increasing with higher number of clusters, levelling out at K = 8 (Φ CT = 0.64, Φ ST = 0.70, Φ SC = 0.17; Table S5). Two levels of structure were distinguished to fit our results: K = 2 and K = 5. At K = 2, the clustering split sampling locations belonging to the Danube drainage basin along with one sampling location of the Alpine Foreland versus all other sampling locations. With increasing number of clusters, the clustering split sampling locations from the (i) Balkans, (ii) eastern Europe, (iii) western and northern Fennoscandia, and (iv) the European Plain. Above K = 5, additional clusters corresponded to single sampling sites which made little biological sense. Therefore, structure at K = 5 (Φ CT = 0.63, Φ ST = 0.70, Φ SC = 0.19) was considered (Fig. 2D). The K = 5 geographic clusters were congruent with results obtained in haplotype networks.

Overall AMOVA based on microsatellites revealed a significant genetic differentiation (F ST =0.21, p-value < 0.05). STRUCTURE analyses based on this dataset identified a best supported value for K = 18 clusters (Fig. S6). Overall, these 18 clusters were consistent with SAMOVA clusters identified with mitochondrial sequences since they appeared as subdivisions of the five SAMOVA clusters: (i) European Plain cluster is subdivided into eleven subgroups, (ii) western and northern Fennoscandia cluster matches with microsatellite subgroups except for the Norwegian sampling site, (iii) eastern Europe cluster is split into three subgroups, (iv) Danube cluster is divided into two subgroups, and (v) Balkans cluster is identical to the mitochondrial one. There were few mismatches with mitochondrial clusters (i.e. in the border areas in southern Fennoscandia, north of the Danube, and in eastern Europe; Fig. 2E).

DISCUSSION

Although similar sampling size is used in several other phylogeographic studies (e.g. Europe, and Russia) should be considered with caution. Indeed, lower sampling efforts could impact the accuracy of genetic diversity estimates or the relevance of population structure analysis. Therefore, we cannot rule out potential artefactual conclusions in these areas.

However, we argue that the observed global phylogeographic patterns are likely since a previous study with higher sampling effort in these areas obtained similar results [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]i.e. specific haplotypes[s] in Scandinavia and southern Europe corresponding to haplotypes found in this study).

Spatial distribution of genetic variability in Perca fluviatilis

Mitochondrial DNA-based analyses show an uneven distribution of the genetic variability (Fig. 2A-B). The observed strong genetic structure between populations (Fig. 2A) shapes five major clusters occurring in different geographic regions of the P. fluviatilis range (Fig. 2D):

(i) the European Plain, (ii) west-northern Fennoscandia, (iii) eastern Europe, (iv) the Danube The geographic pattern of genetic variability identified in the present study slightly differs from previous studies on the European perch (e.g. [START_REF] Christensen | Hatching success in brackish water of Perca fluviatilis eggs obtained from the western Baltic Sea[END_REF][START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF].

Firstly, we detect genetic difference between populations from Danube region and from south-east Europe, which belong to different clusters, while previous studies regarded them as a single unit [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]. Secondly, we highlight the larger geographic range of the European Plain cluster in south-east Europe and Siberia which were previously assigned to the eastern Europe group [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]). These differences are most likely due to the use of different sampling efforts and genetic information. Indeed, current analyses are based on sampling including more populations from Danube and Black Sea regions along with a larger amount of genetic information (i.e. compared to [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF].

Observed geographic pattern of genetic variability is similar to other European freshwater species (e.g. [START_REF] Durand | Phylogeography and postglacial dispersion of the chub (Leuciscus cephalus) in Europe[END_REF][START_REF] Gum | Mitochondrial and nuclear DNA phylogeography of European grayling (Thymallus thymallus): evidence for secondary contact zones in central Europe[END_REF]

Potential shaping factors of the geographic patterns of genetic variability

The observed genetic variability pattern of the European perch can be poorly explained by current barriers to gene flow (e.g. drainage basins, seas). Therefore, we argue that this pattern and large scale population structure have been most likely shaped by past biogeographic events as for other species (e.g. [START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF]Hewitt 2004b[START_REF] Hewitt | Speciation, hybrid zones and phylogeography -Or seeing genes in space and time[END_REF]. We suggest that P. fluviatilis survived to the last Ice-Age in at least three main refugia (i.e. regions currently displaying strong genetic specificities and higher genetic variability; Fig. 2A-B

Considering spatial patterns of genetic variability for Perca fluviatilis aquaculture:

Towards an improved production? [START_REF] Mairesse | Effects of geographic source, rearing system, and season on the nutritional quality of wild and farmed Perca fluviatilis[END_REF][START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF][START_REF] Mélard | Genetic growth improvement of Perca fluviatilis -a review[END_REF][START_REF] Pimakhin | The effect of geographical origin of perch (Perca fluviatilis L. 1758) populations on growth rates under natural and aquaculture conditions: A review[END_REF][START_REF] Pimakhin | Effect of body size on swim bladder inflation in intensively cultured Eurasian perch larvae from different locations[END_REF], Toomey et al. 2019, Vanina et al. 2019a). Moreover, differences in growth and survival rates between several populations (i.e.

Improving P.
Belgian, Finnish, French, and Italian; [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]) correspond to genetically differentiated groups in our analyses (Fig. 2). In the same way, aggressiveness and group structure differ between two Finnish populations and Geneva Lake which belong to different genetic groups (Toomey et al. 2019). Therefore, we suggest that investigations of populations from different genetic groups could allow highlighting populations with divergent performances for aquaculture.

Implications and future guidelines for conservation, management, and production of the European perch

For the time being, the European perch does not seem to be threatened by potential issues that could modify its geographic genetic variability pattern. Indeed, P. fluviatilis (i) is not a threatened species [START_REF] Freyhof | Perca fluviatilis [WWW Document[END_REF]), (ii) has a quite large ecological niche (Kestemont et al. 2015a), (iii) has presumably undergone few within-range translocations (often unintentional; but it can constitute up to 11.6% of unintentionally stocked fishes when stocking material is produced in Polish carp ponds, Kaczkowsk 2006), (iv) is not presumably the subject of restocking programs, and (v) has low dispersion potential (Stepien et al. 2015;[START_REF] -Zamora | Quantifying the activity and movement of perch in a temperate lake by integrating acoustic telemetry and a geographic information system[END_REF]. However, the ongoing development of its aquaculture could change this situation [START_REF] Fontaine | L'élevage de la perche commune, une voie de diversification pour l'aquaculture continentale[END_REF]Kestemont et al. 2015a;[START_REF] Kestemont | Chap. 11 -Aquaculture[END_REF]. Consequently, we argue that production, trade, and translocations of the European perch should be regulated at the nascent stage of the production (see also [START_REF] Allendorf | Ecological and genetic effects of fish introductions: synthesis and recommendations[END_REF] in order to avoid detrimental problems observed for other fish species (e.g. [START_REF] Fleming | Lifetime success and interactions of farm salmon invading a native population[END_REF][START_REF] Lemer | Translocation of wild populations: conservation implications for the genetic diversity of the black-lipped pearl oyster Pinctada margaritifera[END_REF][START_REF] Mazur | Effect of handling and stocking density on hematocrit, plasma cortisol, and survival in wild and hatchery-reared chinook salmon (Oncorhynchus tshawytscha)[END_REF].

In this perspective, prohibition of all importations of wild P. fluviatilis to lands inhabited by distinct genetic populations should be promoted to hamper potential genetic homogenization as well as risks of competition with local populations from the translocation of non-native populations performing better (see for example [START_REF] Michener | The Brazilian bee problem[END_REF][START_REF] Vehanen | Competition between hatchery-raised and wild brown trout Salmo trutta in enclosures -do hatchery releases have negative effects on wild populations?[END_REF].

Moreover, characterizations of current P. fluviatilis farmed stocks have shown specificities compared to wild populations in the neighboring areas of production facilities [START_REF] Khadher | Genetic characterization and relatedness of wild and farmed Eurasian perch (Perca fluviatilis): Possible implications for aquaculture practices[END_REF]. This means that escapees from fish farms could lead to genetic introgression and, potentially, fitness decrease in the wild (i.e. hybrid offspring from wild and domestic parents are often less adapted to local environment; [START_REF] Besnier | Identification of quantitative genetic components of fitness variation in farmed, hybrid and native salmon in the wild[END_REF][START_REF] Bolstad | Gene flow from domesticated escapes alters the life history of wild Atlantic salmon[END_REF][START_REF] Tufto | Domestication and fitness in the wild: A multivariate view[END_REF]. One could expect that using local populations or at least populations belonging to the same genetic group could avoid further issues [START_REF] Youngson | Management of salmonid fisheries in the British Isles: towards a practical approach based on population genetics[END_REF]. However, captive breeding leads rapidly to genetic changes through adaptation to captive environment [START_REF] Williams | Minimizing genetic adaptation in captive breeding programs: A review[END_REF]. Therefore, regulations aiming at limiting gene flow from fish farms should be strongly encouraged, even in indoor aquaculture for which risks cannot be excluded (Summerfelt and Vinci 2009).

Further prospects

The European perch aquaculture is currently at the beginning of its development and we consider that it is a good opportunity to (i) carefully plan future production and translocation management strategies and (ii) investigate genetic units 'intraspecific differentiation of zootechnical traits to improve production. In order to promote a better management strategy, it could also be useful to delineate evolutionarily significant units [START_REF] Moritz | Defining "Evolutionarily Significant Units" for conservation[END_REF], widely used in conservation and fisheries management, by considering other lines of evidence such as phenotypic traits. Here applied to P. fluviatilis, the provision of guidelines through the consideration of spatial patterns of genetic variability could be applied to other socioeconomically interesting species exhibiting intraspecific geographic differentiation. S5: Spatial analysis of molecular variance (SAMOVA) based on the concatenated mitochondrial alignment (16S, COI, D-loop and Cytb) for Perca fluviatilis. Analyses were performed for K values ranging from one to 10 with 10,000 iterations and 10 repetitions. For each K, the best run was selected based on its associated Φ CT (see the text for further details). Colors and numbers indicate the SAMOVA clusters identified for each sampling location for a given value of K. S1.

Translocation regulations

Within-range translocations will most likely increase with production intensification and subsequent trade.

Prohibition of all imports of wild P. fluviatilis to lands inhabited by distinct genetic populations should be promoted to prevent genetic homogenization, outbreeding and competition with wild conspecifics.

Current farmed stocks have genetic specificities compared to wild populations in the neighboring areas of production facilities. Therefore, limiting gene flow from fish farms should be strongly encouraged. demonstrating the usefulness of the multi-function and multi-trait approach since growth is not the only important trait for production, and (iii) elaborating an aquaculture potential index to take into account the variable importance levels of traits studied according to the opinion of stakeholders. This index allows making a consensus between all trait results to identify the PU with the highest aquaculture potential.

WHAT ABOUT GEOGRAPHIC DIFFERENTIATION HIGHLIGHTED IN THE FIRST CHAPTER?

This chapter illustrates steps two and three of the integrative approach. Once the intraspecific classification is established, the different PUs must be evaluated in the same environment with rearing conditions being as close as possible to the domestication system used for production (i.e. common-garden experiment). All PUs were compared in the same domestication environment (same as chapter 1). We hypothesized that divergences in key traits would be sufficiently important to find differences in aquaculture potential between PUs.

Which populations?

In the previous chapter, five PUs were identified. Of these, three were compared: the European Plain, Danube, and Eastern Europe. One population was sampled per unit. In addition, in order to verify that the differentiation intra-PU was lower than the differentiation between PUs, an additional population was sampled for the Eastern European group.

Which traits?

This step required choosing the traits which needed to be evaluated. The focus was placed on traits desired for a successful culture of larvae, namely:

 Growth performance: Growth rate is the main trait of interest when starting a new domestication process (Kestemont et al. 2015a). However, growth rate is more important during on growing than in larviculture. Larval size at hatching is also an important criterion since can influence resistance to starvation [START_REF] Teletchea | Comparison of early life-stage strategies in temperate freshwater fish species: trade-offs are directed towards first feeding of larvae in spring and early summer[END_REF]. During larval stages, it is essential for a farmer to limit growth heterogeneity and, in consequence, reduce time-consuming size sorting to limit aggressive interactions between individuals [START_REF] Fontaine | Domestication et croissance chez les poissons[END_REF]Kestemont et al. 2015a).

 Feed intake capacity: This implies to have in the first stages a sufficiently big yolk sac to survive before exogenous feeding [START_REF] Teletchea | Comparison of early life-stage strategies in temperate freshwater fish species: trade-offs are directed towards first feeding of larvae in spring and early summer[END_REF]. Then, further survival relies on the ability to feed on Artemia and then later on dry feeds (Kestemont et al. 2015a;[START_REF] Król | Effects of stocking density and weaning age on cannibalism, survival and growth in European perch Perca fluviatilis larvae[END_REF].

 Survival rate: Low survival rate is one of the major bottlenecks in perch larviculture. In addition, aggressive interactions can greatly impact productivity (Kestemont et al. 2015a;[START_REF] Naumowicz | Intracohort cannibalism and methods for its mitigation in cultured freshwater fish[END_REF]). These aggressive interactions include notably enucleation (which can be particularly important in European perch; Jourdan 1999) and cannibalism. This latter can be of two types: type I (i.e. when prey is captured tail-first and that ingestion is partial) and type II (when the prey is captured head-first and that the ingestion is total;

Baras 2013). Cannibalism-induced losses can be important, up to more than 50% of the initial stock density [START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF][START_REF] Bandelt | Median-joining networks for inferring intraspecific phylogenies[END_REF]Kestemont et al. 2015a;Król et al. 2015).

 Shoaling behavior: Intensive production implies high rearing densities. Therefore, tolerance to conspecifics is essential (Kristiansen et al. 2004) and a cohesive group structure (relatively to inter-individual distances) is advantageous.

 Activity: This trait is also important since it contributes to the total energetic budget [START_REF] Boisclair | The importance of activity in bioenergetics models applied to actively foraging fishes[END_REF] and less active individuals could contribute to decrease potential aggressive interactions.

 Incidence of deformities and swim bladder inflation: Swim bladder inflation is a crucial process (Policar et al. 2019). Individuals which do not inflate their swim bladder often develop skeletal deformities and display lower growth and survival rates than individuals with inflated swim bladder [START_REF] Jacquemond | Sorting Eurasian perch fingerlings (Perca fluviatilis L.) with and without functional swim bladder using tricaine methane sulfonate[END_REF]Kestemont et al. 2015a). Deformity rate is also essential for production since it hampers survival (Kestemont et al. 2015a;[START_REF] Alix | Deformities in newly hatched embryos of Eurasian perch populations originating from two different rearing systems[END_REF].

All these parameters (except for enucleation which is specific to the studied model) were previously listed in the second chapter.

ABSTRACT

In agriculture, diversifying production implies picking up, in the wild biodiversity, species or populations that can be domesticated and fruitfully produced. Two alternative approaches are available to highlight wild candidate(s) with high interest for aquaculture: the single-trait (i.e.

considering a single phenotypic trait and, thus, a single biological function) and multi-trait (i.e. considering multiple phenotypic traits involved in several biological functions) approaches. Although the former is the traditional and the simplest method, the latter could be theoretically more efficient. However, an explicit comparison of advantages and pitfalls between these approaches is lacking to date in aquaculture. Here, we compared the two approaches to highlight best candidate(s) between four wild allopatric populations of Perca fluviatilis in standardized aquaculture conditions. Our results showed that the single-trait approach can (i) miss key divergences between populations and (ii) highlight different best candidate(s) depending on the trait considered. In contrast, the multi-trait approach allowed identifying the population with the highest domestication potential1 thanks to several congruent lines of evidence. Nevertheless, such an integrative assessment is achieved with a far more time-consuming and expensive study. Therefore, improvements and rationalizations will be needed to make the multi-trait approach a promising way in the aquaculture development.

Key words: Multi-criterion approach, Trait, Intraspecific variability, Geographic origin, Domestication, Aquaculture

INTRODUCTION

The emergence of agriculture is one of the most important evolutions in human history. It was enabled by wild species domestication [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF]. Domestication is the process in which groups of individuals are bred in a human-controlled environment and modified across succeeding generations from their wild ancestors, in ways these become more useful to humans who increasingly control their food supply and reproduction [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]. This process ranges from the first trials of acclimatization to the setting up of selective breeding programs [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]. The main wave of domestication for fishes only started at the beginning of the 20 th century to develop aquaculture (i.e. the farming of aquatic organisms), notably to mitigate provisioning service disruptions due to fishery collapse [START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]FAO 2018). Aquaculture is the fastest-growing food production sector in the world and now provides about 50% of the world's aquatic food consumption (FAO 2018). However, the aquaculture development has been criticized, notably because of its negative consequences on environments and its potential unsustainable development [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF][START_REF] Christou | Sustainable Food Production[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF].

Despite the numerous attempts to domesticate new fish species, one of the main weaknesses of today's aquaculture is its low species diversity (i.e. 85% of world fish production relies on about fifteen species; Lazard 2013). Indeed, this latter threatens (i) wild native fauna (e.g. biological invasions, pathogen spill over; Naylor et al. 2005;[START_REF] Silva Ss De | Alien Species in Aquaculture and Biodiversity: A Paradox in Food Production[END_REF]; Martinez-Porchas and Martinez-Cordova 2012), (ii) food security (e.g. epizooty hazard; [START_REF] Godoy | First detection, isolation and molecular characterization of infectious salmon anaemia virus associated with clinical disease in farmed Atlantic salmon (Salmo salar) in Chile[END_REF], and (iii) economic prospect (e.g. low adaptive potential to face environment/market fluctuations; [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF]). This alarming situation has triggered a new trend in aquaculture development: the production diversification to enhance the sustainability of the sector [START_REF] Fontaine | Domestication de nouvelles espèces et développement durable de la pisciculture[END_REF]FAO 2018).

Promoting species production diversification is not an easy task since it implies domesticating and commercially producing new species. This often fails due to either technical limitations, economic constraints, or intrinsic species features [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]; see also for non-fish species [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF][START_REF] Dehaan | A pipeline strategy for grain crop domestication[END_REF]. These latter features are, for instance, low growth rate, high aggressiveness level, or low tolerance to high rearing densities, which are seen as impeding traits to start fruitful species production [START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]). On the opposite, the ability to grow, feed, reproduce, and tolerate conspecifics and aquaculture-induced stress facilitates domestication [START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]. This means that the predisposition to be successfully domesticated and produced is speciesdependent [START_REF] Jobling | Farmed species and their characteristics[END_REF]. Furthermore, these features could also vary at the intraspecific level, especially due to geographic differentiation (e.g. [START_REF] Purchase | Interpopulation differences in growth rates and food conversion efficiencies of young Grand Banks and Gulf of Maine Atlantic cod (Gadus morhua)[END_REF]Toomey et al. 2019). Indeed, this differentiation between geographically distant conspecific populations [START_REF] Mayr | Animal species and evolution[END_REF], triggered by distinct demographic histories and local adaptations, can shape population specificities in key features for domesticating and commercially producing fishes (e.g. growth and development; [START_REF] Marcil | Genetic and environmental components of phenotypic variation in body shape among populations of Atlantic cod (Gadus morhua L.)[END_REF]Vanina et al. 2019a). Therefore, taking into account geographic differentiation could facilitate new species domestication (Toomey et al. 2019;Vanina et al. 2019a).

Evaluating the ability of a species/population to be successfully domesticated and commercially produced requires an initial assessment of its expression of key trait(s). Looking back at past domestication programs, two alternative paradigms can be used to identify species or population(s) of interest for further production development: the (i) single-trait and

(ii) multi-trait approaches.

The single-trait assessment is the traditional approach which consists of studying a single phenotypic trait, and consequently a single biological function, to highlight population(s) with desirable expression of the trait for further production development. This approach has been widely applied at the beginning or at advanced stages of the domestication process in agriculture of animals (e.g. [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF][START_REF] Rauw | Undesirable side effects of selection for high production efficiency in farm animals: a review[END_REF][START_REF] Pryce | Fertility in the high-producing dairy cow[END_REF]Gjedrem 2005a;[START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF][START_REF] Dugatkin | The silver fox domestication experiment[END_REF]; see also for plants: [START_REF] Chabriat | La tomate, les défis du goût[END_REF].

Single-trait assessments often focus on an easily measurable trait which expression is involved in the domestication process and/or production profitability. Most of the time, growth rate is considered as a premium criterion (Gjedrem 2005a[START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. This was for instance the case with Nile tilapia (Oreochromis niloticus), which domestication programs initially focused on the growth rate [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF]; see for other species: [START_REF] Nguyen | Perspectives from agriculture: advances in livestock breedingimplications for aquaculture genetics[END_REF][START_REF] Rye | Genetic improvement programs for aquaculture species in developed countries[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]). However, other traits are sometimes considered. For example, the beginning of the silver fox (Vulpes vulpes fulvus) domestication programs focused on tameness [START_REF] Trut | Early Canid Domestication: The Farm-Fox Experiment: Foxes bred for tamability in a 40-year experiment exhibit remarkable transformations that suggest an interplay between behavioral genetics and development[END_REF][START_REF] Dugatkin | The silver fox domestication experiment[END_REF], which facilitates the domestication process [START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF]). In the same way, selective breeding programs in land agriculture have often focused on fertility [START_REF] Pryce | Fertility in the high-producing dairy cow[END_REF]). Therefore, alternative choices of traits could be considered to perform the single-trait approach.

The multi-trait approach has recently been raised as an alternative method to the single-trait assessment. It has been suggested as a promising way to overcome domestication bottlenecks (e.g. Gjedrem 2005a;[START_REF] Miglior | Selection indices in holstein cattle of various countries[END_REF][START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF][START_REF] -Lachambre | Relationships between growth, survival, physiology and behavior -A multi-criteria approach to Haliotis tuberculata phenotypic traits[END_REF]. It assumes that a successful domestication process requires the favorable expression of several traits involved in various biological functions. Indeed, it is possible to successfully domesticate a population if it can reproduce, feed, grow, and overcome stresses in a humancontrolled environment (Gjedrem 2005a;[START_REF] Miglior | Selection indices in holstein cattle of various countries[END_REF]. First applied in land agriculture (e.g. [START_REF] Miglior | Selection indices in holstein cattle of various countries[END_REF], this approach is now promoted in fish aquaculture, especially at advanced stages of domestication (Gjedrem 2005a[START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF][START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF]. At these advanced stages, growth performance, morphology, disease resistance, flesh quality traits, age at sexual maturation, and feed efficiency have been considered (Gjedrem 2005a;[START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF]). However, it is still poorly considered at the beginning of the domestication processes (i.e. first trials of acclimatization of new candidates) even though a few examples exist (population [START_REF] Gjedrem | The first family-based breeding program in aquaculture[END_REF]] or species selections [Alvarez-Lajonchère and Ibarra-Castro 2013]).

Although the multi-trait approach is the focus of an increasing research, an explicit assessment of its advantages and its pitfalls has not been performed to date. Indeed, no comparison between single-trait and multi-trait approaches to highlight best wild populations for fish aquaculture is currently available. Here, we compare the potential interest for aquaculture of four wild allopatric populations of a test-case species, the European perch (Perca fluviatilis), during the larval period using the two different paradigms. We hypothesize that these two approaches lead to divergent conclusions.

RESULTS

We studied four wild lakes (Appendix S1): Valkea-Müstajärvi (VAL), Iso-Valkjärvi (ISO), Geneva (GEN), and Balaton (BAL). We compared populations at the larval stage based on 12 traits involved in growth, development, nutrition, and behavior (Fig. 12). These traits can impact the ability to be domesticated and fruitfully produced in aquaculture. For the singletrait approach, we considered all possibilities of initial trait choice. This means that we performed independent assessments of aquaculture interest based on each trait independently.

For the multi-trait approach, we achieved an integrative assessment by using a domestication potential index (Table 1; Appendix S2) to reach a consensus between results observed for all traits considered. The calculation of the domestication potential score was possible thanks to a CHAPTER 4 153 survey addressed to perch farmers, which allowed to assign to each trait an average weighting coefficient (i.e. level of importance according to perch farmers). Correlations between traits were evaluated in order to determine if there were redundant traits in the multi-trait assessment. All details are in the Material and Methods section. Table 1. Domestication potential score obtained for the four Perca fluviatilis wild populations in the multi-trait analysis. ISO : Lake Iso-Valkjärvi, VAL : Lake Valkea-Müstajärvi, GEN : Lake Geneva, BAL : Lake Balaton. 155

Inter-populational differences in phase I

No statistical difference between populations was found for final length heterogeneity (F (3,8; where 3 corresponds to the first degree of liberty [number of populations-1] and 8 to the second degree of liberty [total number of replicatesnumber of populations]) =1.27, p-value=0.35) and activity (F (3,32) =2.79, p-value=0.06).

A significant statistical difference between populations was found for the swim bladder inflation rate (F (3,8) =19.79, p-value=4.65x10 -4 ), survival rate (F (3,8) =7.29, p-value=0.019), deformity rate (F (3,8) =22. 88, p-value=2.80x10 -4 ), length at hatching (F (3,8) =12.45, p-value=2.87x10 -3 ), yolk sac volume (F (3,8) =10.85, p-value=2.21x10 -3 ), and for the mean of inter-individual distances (F (3,32) =10.22, p-value=7.12x10 -5 ) (Fig. 1). The figure 1 summarizes which population(s) tend to display the most desirable expression value for each trait.

Inter-populational differences in phase II

No statistical difference between populations was found for specific growth rate in length (F (3,8) =2.20, p-value=0.17 A statistically significant difference was found between populations (Fig. 2) for swim bladder inflation rate (F (3,8) =22.97, p-value=1.36x10 -4 ), survival rate (F (3,8) =4.60, p-value=0.040), deformity rate (F (3,8) =6.95, p-value=0.013), activity (F (3,32) =15.77, p-value=1.79x10 -6 ), and the mean of inter-individual distances (K=8.25, df=3, p-value=0.041) (Fig. 2). The figure 2 summarizes which population(s) tend to display the most desirable expression value for each trait.

Evaluation of the population interest for domestication

Regarding the single-trait approach, populations' interests for aquaculture differed depending on the trait initially chosen and were not consistent across experimental phases. Indeed, the best population is not the same depending on which trait is considered to perform the singletrait analysis (Fig. 12). For instance, when considering only growth rate, it did not allow identifying a differentiation in the interest for domestication between populations. On the contrary, when considering deformity rate, GEN appeared as the least suitable population in both phases. In the same way, when considering swim bladder inflation rate, BAL presented the highest interest for domestication in phase I but that would hide the fact that this population presented in phase II the highest activity rate (Fig. 12). Regarding the multi-trait approach, it highlighted that the population with the highest domestication potential score is BAL, followed by ISO, VAL, and GEN (Table 1; Appendix S2).

Phenotypic correlations

Very few correlations were highlighted: 14 pairs of traits were positively correlated (p-value<0.05), 13 pairs were negatively correlated (p-value<0.05), and 144 pairs were not significantly correlated (Appendix S3).

DISCUSSION

Our results were based on a common garden experiment which allows investigating the genetic basis of phenotypic differences (i.e. heritable divergences) between populations [START_REF] Hutchings | Old wine in new bottles: reaction norms in salmonid fishes[END_REF]. Therefore, it is an efficient way to compare larviculture performances between several wild populations. However, some limitations must be underlined. Indeed, evaluations were based on individuals originating from eggs collected from the wild.

Therefore, we cannot completely rule out that some of the observed trait expressions had been shaped by phenotypic plasticity (i.e. the ability of a genotype to display several phenotypes when exposed to different environments; [START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF] or transgenerational effects [START_REF] Youngson | Transgenerational epigenetic effects[END_REF]. Therefore, aquaculture performances of the four studied European perch populations should be considered with caution by fish farmers. Nevertheless, we argue that we minimized these potential biases thanks to our common-garden environment. Moreover, if such limitations ever impact our results, they would affect both the single-trait and the multi-trait approaches. Finally, this study aimed at comparing the two approaches rather than highlighting the best biological unit for larviculture within P.

fluviatilis. Further comparisons between populations over the entire lifecycle using the multitrait approach would allow identifying within species the best unit to further develop P. fluviatilis production.

When the simple way fails

Our study shows that the alternative single-trait and multi-trait approaches can lead to divergent results when highlighting the best population(s) for aquaculture purpose.

Overall, we detect three main limitations of the single-trait approach. First, considering a single trait can lead to miss the potential available in the wild biodiversity if the targeted trait does not vary between studied populations. This is particularly noticeable for the growth rate (no significant differentiation between populations despite a differential length at hatching; Fig. 1), which has traditionally been the most considered trait when assessing performances in aquaculture [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF]Gjedrem 2005a;[START_REF] Rye | Genetic improvement programs for aquaculture species in developed countries[END_REF]). In the worst-case scenario, this would lead to start a production with a suboptimal population that will have to be improved through costly and difficult selective breeding programs while better candidates were available in the wild. Second, the identification of populations with the highest interest for aquaculture can vary depending on the trait picked for evaluation. For instance, the observed differentiations for survival and deformity rates allow identifying best population(s)

for aquaculture but do not converge to highlight the same best population(s) (Fig. 2).

Furthermore, some of the conclusions obtained by the alternative tested single-trait approaches are completely contradictory (e.g. deformity rate would highlight Lake Balaton as the one of the best populations while if activity is considered, it would qualify this population as the least suitable; Fig. 12). This places a premium on the definition of the most important trait for fish production although this is still unachievable information due to divergent opinions between fish farmers and the numerous traits evaluated as very important (e.g.

Appendix S2

). Third, the choice of a population based on a single trait, and consequently a single biological function, can lead to start fish domestication/production with a population displaying deleterious expression of other key traits. Indeed, since traits are linked in complex ways, selection of only one trait will inevitable be associated with the indirect selection of other traits (i.e. through linkage and/or pleiotropy; [START_REF] Akdemir | Multi-objective optimized genomic breeding strategies for sustainable food improvement[END_REF], including undesirable characteristics [START_REF] Mackay | Introduction to quantitative genetics[END_REF][START_REF] Grandin | The way I see it : the dangers of trait over-selection[END_REF]. Eventually, this leads to deleterious impacts of the species production [START_REF] Nguyen | Perspectives from agriculture: advances in livestock breedingimplications for aquaculture genetics[END_REF]. This last limit is a well-known fact in land species domestication history (but see for aquaculture negative genetic correlations, e.g. [START_REF] Bangera | Negative genetic correlation between resistance against Piscirickettsia salmonis and harvest weight in coho salmon (Oncorhynchus kisutch)[END_REF]. For instance, continuous selection towards milk yield and growth led respectively to a decrease of (i) fertility in dairy cow [START_REF] Pryce | Fertility in the high-producing dairy cow[END_REF] and (ii) reproductive and immune performances in broilers [START_REF] Rauw | Undesirable side effects of selection for high production efficiency in farm animals: a review[END_REF]). In the same way, artificial selection in domestic turkeys for large breast size has led to the artificial insemination of females due to the inability of males to copulate naturally [START_REF] Price | Behavioral development in animals undergoing domestication[END_REF].

Similarly, the focus on taming at the beginning of the domestication process of the silver fox (Vulpes vulpes fulvus) led to morphological changes disadvantageous for the pelt market [START_REF] Dugatkin | The silver fox domestication experiment[END_REF].

More is more but it is more complicated too

Multi-trait approach allows overcoming the single-trait method limitations. Indeed, investigating several traits minimizes the risk of missing valuable populational specificities or choosing a population with hidden undesirable characteristics. Therefore, the nascent promotion of multi-trait approach in land and aquatic agriculture development (Gjedrem 2005a;[START_REF] Akdemir | Multi-objective optimized genomic breeding strategies for sustainable food improvement[END_REF]) is a timely and welcomed trend. Moreover, it provides a more efficient and realistic assessment to start new domestication processes and to increase the sector sustainability since they both involve several biological functions that could be studied only through the consideration of many traits. Indeed, as mentioned before, the domestication itself involves several biological functions such as growth, nutrition, behavior, and reproduction. Moreover, the willingness to develop a more sustainable aquaculture production implies for instance to study traits involved in robustness (e.g. resistance to thermal changes, vulnerability to new pathogens/parasites) and nutrition (e.g. ability to grow with a plant-based diet) (FAO 2018). However, beyond the bright sides of multi-trait approach, three main limitations could make its implementation difficult.

First, the most obvious pragmatic issue is that workload and cost associated with this approach are much more substantial than with the single-trait approach. Nevertheless, the complexity of multi-trait assessment should be seen as balanced by choosing the best part of the wild biodiversity before starting large-scale domestication programs which are far more expensive and time-consuming. Second, methodological limitations could impede the relevance of the multi-trait and multi-function approach. Indeed, the lack of efficient methods to measure some traits (e.g. assessment of traits involved in the nutrition function such as food conversion ratio requiring complex protocol, [START_REF] Gjedrem | Selective Breeding in Aquaculture: An Introduction[END_REF] and the increased risk of errors when working on multiple traits could lead to false decisions when choosing candidates for domestication/production. Finally, working with multiple traits implies using a method to make a consensus between results obtained for individual traits. Here, we proposed a scoring method in order to highlight within species a biological unit of interest. This method presents the inconvenience of not highlighting deltas of difference between populations since ranks are used to classify populations (see Material and Methods section for calculation details; Appendix S2). However, it allows putting all traits at the same level and then uses weighting coefficient to take into account trait importance divergences according to fish farmers. Other alternative methods could have been used but, nowadays, there is no consensus about which method should be favored (e.g. using the majority rule: the best population is the one which is ranked first for a majority number of traits; it would also highlight Lake Balaton as the best population but does not take into account divergent levels of importance of the traits; Appendix S2).

How to facilitate the multi-trait approach?

Although research advances are making (i) fish trait information available or (ii) trait analysis methods easier and cheaper, reckless integration of many traits in the multi-trait approach could make the previously cited limitations worsen. Therefore, this places a premium on restricting the assessment framework to a limited set of relevant traits. Such an optimization could be achieved through (i) socio-economical/biological considerations and (ii) trait correlation assessments. First, only traits which are relevant for domestication and/or production need to be considered. Such a finite list of relevant traits can be achieved through stakeholder involvement in the assessment framework design. Here, for instance we only considered traits that were regarded as relevant by the majority of questioned fish farmers (Appendix S2), considering only biological functions which are relevant for the studied lifestage. Second, some traits could be removed from the assessment framework by considering phenotypic correlations between traits (assuming phenotypic correlations are a good proxy for genetic correlations ;[START_REF] Cheverud | A comparison of genetic and phenotypic correlations[END_REF][START_REF] Roff | The evolution of genetic correlations ; an analysis of patterns[END_REF]. Indeed, when such correlations are observed (e.g. feed efficiency improvement when growth rate considered [START_REF] Kause | Feed efficiency of rainbow trout can be improved through selection: Different genetic potential on alternative diets[END_REF][START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF], aggressiveness decrease when growth rate considered [START_REF] Johnsson | Domestication and growth hormone alter antipredator behavior and growth patterns in juvenile brown trout, Salmo trutta[END_REF]), one could expect that by focusing on a few traits, it is possible to take into account expressions of other correlated traits. However, in our study, we highlighted only few correlations including biological non-relevant relationships (e.g. positive correlation between length at hatching and activity in phase II). Therefore, this suggests that considering trait correlations may not be helpful, at least in some cases, to restrict the evaluation to a handful of traits.

CONCLUSION

Our results highlighted that the single-trait approach can (i) miss key divergences between the populations and (ii) highlight different best candidate(s). Conversely, the multi-trait approach, which includes several key traits for larviculture, allowed identifying the population with the highest domestication potential thanks to several congruent lines of evidence. Nevertheless, this approach is more complex and requires making consensus between trait results. However, despite these limitations, it appears as the most suitable approach to highlight within species populations with higher domestication potential.

MATERIAL AND METHODS

Test-case species

Perca fluviatilis (Actinopterygii, Percidae) is a common widely spread Eurasian species living in freshwater and brackish habitats (Kestemont et al. 2015a). Its economic (high market value) and recreational (i.e. fishing) interests have led to the development of its RAS (i.e.

recirculating aquaculture systems) farming since the 1990's (Kestemont et al. 2015a). Perca fluviatilis is among the most interesting species for the development of inland aquaculture in Europe (Kestemont et al. 2015a). However, despite its economic potential, the production is still limited. This is mainly due to major bottlenecks, especially in first-life stages, such as low growth rate, low survival rate, and high cannibalism rate (Kestemont et al. 2015a). This highlights the potential interest of re-starting new domestication programs. An intraspecific differentiation was already highlighted for this species in standardized conditions (e.g. growth [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF]Vanina et al. 2019a], behavior [Toomey et al. 2019], development [START_REF] Pimakhin | Effect of body size on swim bladder inflation in intensively cultured Eurasian perch larvae from different locations[END_REF]).

Biological material collection and pre-experiment rearing conditions

Population sampling and rearing conditions were adapted from Toomey et al. (2019). Egg Finland; 61°13'08"N, 25°07'05"E), Iso-Valkjärvi (ISO; 2018; Finland; 60°57'21"N, 26°13'3"E), Geneva (GEN;2019;France;46°22′7.20"N, 6°27′14.73"E), and Balaton (BAL ;2019 ;Hungary ;46°54'23.375"N, 18°2'43.119"E). We chose these populations since a phenotypic differentiation is known between the Finnish and Geneva populations (Toomey et al. 2019) while genetic specificities of central Europe populations have been already observed [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]Vanina et al. 2019b). After transportation, 13 to 19 egg ribbons per lake were incubated at the experimental platform of aquaculture (Unit of Animal Research and Functionality of Animal Products, University of Lorraine, Vandoeuvre-lès-Nancy, France) at 13 °C in incubators (110x64x186cm; one incubator per population) containing nine racks each (45x7x12cm). Each incubator had its own temperature control and recirculated water system (flow rate of 4m 3 .h -1 ). Water was UV-sterilized. Temperature (13.0 ± 0.4 °C) and oxygen rate (10.0 ± 0.5 mg.L -1 ) were checked daily while pH (8.0 ± 0.2) was monitored three times a week (± standard error). Ammonium and nitrite concentrations (lower than 0.05 mg.L - 1 ) were measured three times a week until hatching. Light intensity was 400 lx at the water surface. Photoperiod was 12L:12D (12 hours of light and 12 hours of darkness).

Experimental rearing protocol

Two independent experimental phases were performed: phase I from hatching until the end of weaning (i.e. transition from live feed to inert pellets; 26 days post-hatching, dph) and phase II from 27 dph until the end of nursery, at 60 dph. The larval period was split in two phases in order to ensure availability of larvae across the whole larval period since there is a very high mortality rate during first-life stages. Because wild egg ribbons are not available the same time for all populations (i.e. asynchronous spawning seasons) and in order to prevent potential pathogen transmission, all populations were reared in independent structures. Since there are increasing concerns about the epizootic disease Perhabdovirus in Europe (Kestemont et al. 2015a), all populations were tested for the occurrence of this virus (Laboratoire Département d'Analyses du Jura, Poligny, France). All results were negative to the presence of the Perhabdovirus.

Regarding phase I, larvae from the different egg ribbons of each population were mixed after Regarding phase II, after hatching, larvae left (i.e. not sampled for phase I) were held in 2 m 3 tanks (RAS). The same conditions as phase I were used (temperature, light intensity, feeding, and photoperiod regimes). At 27 dph, these larvae were transferred to the three cylindroconical tanks in order to start phase II at a density of 19 larvae.L -1 . Light intensity was 80 lx at water surface, all else remaining the same as phase I (except for density).

Behavioral traits

The ability of a biological unit to be efficiently produced in intensive conditions (i.e. intensive farming is an increasing trend in the aquaculture development) also depends on (i) interindividual relationships, (ii) inter-individual distances, and (iii) activity (Toomey et al. 2019).

Indeed, tolerance to conspecifics in a restricted area is essential for production since it can impact individual welfare [START_REF] Huntingford | Implications of domestication and rearing conditions for the behavior of cultivated fishes[END_REF]. Highlighting populations which present a cohesive group structure would be advantageous. Nevertheless, living in group is not costless because it can trigger aggressive behaviors which can lead to uneven competition for food, mortalities, stress, or immune suppression (Toomey et al. 2019). Therefore, both interindividual distances and inter-individual interactions need to be considered. Finally, activity is also important since it contributes to the total energetic budget (Toomey et al. 2019).

Furthermore, less active individuals could contribute to decrease the occurrence of interindividual contacts and subsequent potential aggressive interactions.

Regarding aggressive interaction quantification, aggressiveness was calculated for phase II for later length measurements. Larvae tested in the circular arenas from ISO, VAL, BAL, and GEN were respectively 14.05 ± 0.55 mm, 12.90 ± 0.62 mm, 10.62 ± 0.47 mm, and 11.81 ± 1.01 mm during phase I and 26.74 ± 1.67 mm, 26.28 ± 1.99 mm, 19.24 ± 1.22 mm, and 12.26 ± 0.45 mm during phase II (± standard error). Analyses were performed using the ImageJ software. Images were extracted from videos at five-minute interval (six images per video).

For each image, coordinates of individuals were noted using the middle point between the eyes. The mean of inter-individual distances was evaluated per replicate. It corresponds to the mean of distances between a focal fish and all the other fish of the group and it is an indicator of the group cohesion. Detailed calculation is available in [START_REF] Colchen | Temperature modifies activity, inter-individual relationships and group structure in fish[END_REF]. Activity was analyzed in ImageJ. Every five minutes, one image per second was extracted for six consecutive seconds. For each image, coordinates of each individual were noted. This allowed calculating distance swam every second during the five seconds. The mean allowed obtaining for each individual the mean distance swam per second. From these values, we were able to calculate an average activity per replicate.

Growth traits

Growth traits are important in larviculture production, more particularly the length at hatching, specific growth rate, and growth heterogeneity (Kestemont et al. 2015a). To evaluate these traits, 30 larvae per population (i.e. ten larvae per cylindro-conical tank) were sampled the first and last days of each experimental phase, euthanized with an overdose of MS-222, and kept in formalin 4 %. For phases I and II, larvae were measured using ImageJ (± 0.01 mm). For phase II, larvae were also individually weighted (± 0.1 mg; not possible in phase I due to the imprecision of measure at one day post-hatching). Since specific growth rate (SGR) is a trait of interest at the end of larviculture, it was calculated only in phase II using the following formula: SGR=100*(ln(Xf)-ln(Xi))*∆T -1 where Xi and Xf are respectively the average initial and final weight/length and ∆T the duration of phase II. Final growth heterogeneity was calculated for both phases in the following way: CV Xf / CV Xi in which CV is the coefficient of variation (100* standard deviation/mean) and Xi and Xf the initial and final weight/length, respectively.

Statistical analyses

All statistical analyses were performed in R 3.0.3 to assess if there were statistical differences (p-value<0.05) in traits between populations. To test the normality of distribution, a Shapiro-Wilk test was used. Homogeneity of variances was tested using the Levene test (R-package lawstat). When assumptions were not met, data was log-transformed. Then, in order to check if the cylindro-conical tank had no influence on our results, Corrected Akaike Information Criterion (AICc; R-package qpcR) were used to compare linear mixed models (biological traits as fixed factors and cylindro-conical tanks as random factor; R-package lmer) and linear model (biological traits as fixed factors, no random factor). For most factors, there was no influence of the cylindro-conical tank on the model. Therefore, one-way analyses of variance (ANOVA F test) followed by Tukey post hoc tests were used to evaluate differences between populations. When the effect of the cylindro-conical tank was significant, the ANOVA was performed on the linear mixed model and estimated marginal means were calculated (Rpackage emmeans). When assumptions were not respected despite log-transformation (only for inter-individual distances in phase II), Kruskal-Wallis H test was used followed by Dunn post-hoc test (R-package PMCMR). All post-hoc results were corrected relatively to the number of comparisons using Benjamini-Hochberg procedure. In order to improve the multitrait approach, we assessed if there were redundant traits in the assessment. To do so, Pearson's correlation coefficients between traits were calculated (except for correlations with inter-individual distances in phase II for which Spearman's correlation coefficients were calculated).

Evaluation of the population interest for domestication with the two approaches

Regarding the single trait analysis, growth rate is the most often considered trait in domestication programs. However, in this study, we considered all possibilities of initial trait choice and analyzed results for all alternative cases. This means that we obtained independent assessments of aquaculture interest based on each trait independently. Providing a statistical difference is observed, we considered as the best population(s), the one (those) which displayed the most desirable expression (from a fish farmer point of view, Kestemont et al. 2015a). The expression value considered is the mean obtained over the three replicates.

In the multi-trait approach, an integrative decision framework is necessary in order to make a consensus between the different traits. Indeed, it is unlikely that a population has the best performances for all criteria. It is more likely that a unit displays the best performance for a specific trait (e.g. best growth rate) but the worst for another (e.g. lowest larval survival rate).

Therefore, an indicator is required in order to make a synthesis at the multi-function and multi-trait levels to identify units with high domestication potential. Some methods and associated scores were suggested at the interspecific level in order to identify good candidate Highlighting the best candidates to start domestication and subsequent production relies on difficult and time-consuming bioassays. Since it is not feasible to compare performances of all populations across a species distribution range, we used in previous steps a genetic proxy to group populations. The results obtained in the first and fourth chapters are congruent with the classification established in the third chapter. Indeed, differentiation for key traits was observed between populations belonging to different PUs. In addition, differentiation is overall stronger between populations belonging to different PUs than between the two Finnish populations which belong to the same PU. However, the verification that the intra-PU differentiation was lower than the inter-PU differentiation was only performed with two populations. Therefore, the relevance of the genetic classification can be questioned.

In this chapter, we assessed the relevance of three alternative proxies (i.e. genetic, habitat, and hydrologic/geographic proxies) to highlight inter-populational divergences in key traits for larviculture in P. fluviatilis. In order to evaluate the relevance of these three proxies, we used larval performance results obtained on seven populations of P. fluviatilis. This higher number of populations allowed to (i) better consider the geographic differentiation and potential intra-PU differentiation and (ii) integrate populations geographically/hydrologically distant and potentially presenting different selective pressure regimes.

INTRODUCTION

Inter-populational differentiation (i.e. differentiation between allopatric, peripatric, or parapatric conspecific populations; e.g. see in fishes [START_REF] Blanck | Large-scale intraspecific variation in life-history traits of European freshwater fish[END_REF] and insects [Lecocq et al. 2015]) can result from specific demographic history, limited gene flow, random genetic drift, and/or local adaptations [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]. Often considered in evolutionary and conservation biology [START_REF] Frankham | Introduction to Conservation Genetics[END_REF], analyzing and exploiting interpopulational phenotypic differentiation is also of crucial interest for agriculture development.

Indeed, populations can present divergent expressions of key traits (i.e. phenotypic traits which are important for domestication and subsequent production; e.g. for fishes; Alvarez-Lajonchère and Ibarra-Castro 2013). Therefore, considering population specificities could allow identifying population(s) presenting different domestication potentials (i.e. most interesting expression of key traits). This could ultimately facilitate domestication [START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF]) programs of a new species and its subsequent production. Several success-stories have highlighted the interest of considering inter-populational specificities. For instance, the bufftailed bumblebee (Bombus terrestris), which has been domesticated to act as pollinator in greenhouses, displays phenotypic differentiations between allopatric wild populations for traits impacting its ability to be industrially produced and to pollinate valuable crops [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF]. At the beginning of its production, bumblebee breeders tried to rear several wild populations [START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF] and, eventually, identified one with superior characteristics, triggering a flourishing development of the bumblebee production industry (Lecocq et al. 2016b). Similarly, the development of the Atlantic salmon (Salmo salar) industry was facilitated by reaping the benefits from inter-populational differentiation.

Indeed, initial comparisons of several key traits for fish farmers (e.g. growth rate, disease resistance) between wild populations allowed identifying those with higher performances which were then used as cornerstone fish stock of salmon production [START_REF] Gunnes | Selection experiments with salmon IV Growth of Atlantic Salmon during two years in the sea[END_REF][START_REF] Gjedrem | The first family-based breeding program in aquaculture[END_REF]. Beside new domestication instances, wild intraspecific differentiation can also be used to enhance old-established species farming, because introduction of adaptive traits (i.e. genomic introgression) from wild populations can lead to phenotypic novelty in produced stocks [START_REF] Warschefsky | Back to the wilds: Tapping evolutionary adaptations for resilient crops through systematic hybridization with crop wild relatives[END_REF].

Given the potential benefits of considering inter-populational phenotypic differentiation in domestication/farming programs, there is a premium on highlighting wild populations with divergences in key traits. This requires population assessments that can only be achieved through bioassays in which expressions of key traits are evaluated in a common experimental environment (i.e. common garden) close to future farming conditions. Indeed, similar assessments in natura would be doubtful because (i) some traits cannot be characterized during fieldworks due to technical reasons, and/or (ii) trait expression is the result of both genetic and environmental factors. The latter point is the main issue because phenotypic plasticity (sensu [START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF] can shape observed divergences between wild populations. However, such divergences would be useless for domestication programs because they will not be (i) observed in ex-situ farming and (ii) conserved in future production environment. Only genetic differentiations are of interest for domestication because production occurs in a system that is often quite different from the wild environment. The common-garden experiment is an efficient way to assess such differentiations. Indeed, it can highlight inter-populational divergences with a genetic basis [START_REF] Hutchings | Old wine in new bottles: reaction norms in salmonid fishes[END_REF]). However, it is not feasible to evaluate trait expressions in experimental conditions for all populations inhabiting the species distribution range. Moreover, from a phenotypic perspective, populations are not all notably divergent from each other, making comprehensive assessments uselessly time/money consuming. One solution relies on limiting potential comparisons before performing bioassays by (i) gathering populations that are likely undifferentiated, or (ii) highlighting population groups that most likely display specificities or, at least, divergences in key traits.

Already available intraspecific taxonomic classifications like subspecies [START_REF] Mayr | Systematics and the Origin of Species[END_REF] historically widely defined, e.g. [START_REF] Haig | Taxonomic Considerations in Listing Subspecies Under the U.S. Endangered Species Act[END_REF][START_REF] Braby | The subspecies concept in butterflies: has its application in taxonomy and conservation biology outlived its usefulness?[END_REF]) could provide the needed population shorting (i.e. inter-populational differentiation of key traits in B. terrestris matches with the subspecies; Lecocq et al. 2016b). However, these taxonomic statuses have been fiercely criticized because (i) their relevance for systematics and (ii) criteria that should be considered for their definitions are doubtful [START_REF] Phillimore | Are subspecies useful in evolutionary and conservation biology?[END_REF][START_REF] Braby | The subspecies concept in butterflies: has its application in taxonomy and conservation biology outlived its usefulness?[END_REF].

This has triggered a trend to eliminate the trinomial designation in several species groups (e.g. [START_REF] Mulcahy | Phylogeography and species boundaries of the western North American Nightsnake (Hypsiglena torquata): revisiting the subspecies concept[END_REF][START_REF] Torstrom | Shedding subspecies: The influence of genetics on reptile subspecies taxonomy[END_REF]. In conservation biology, evolutionarily significant units, management units, distinct population segments, or designatable units, have been proposed to complement existing taxonomy and/or to go beyond systematists' feud [START_REF] Frankham | Resolving taxonomic uncertainties and defining management units[END_REF][START_REF] Maxted | Establishment of a global network for the in situ conservation of crop wild relatives: status and needs. Commission on genetic resources for food and agriculture[END_REF][START_REF] Mee | Identifying designatable units for intraspecific conservation prioritization: a hierarchical approach applied to the lake whitefish species complex (Coregonus spp.)[END_REF]. However, their interpretations and definition criteria vary among species and scientists (e.g. [START_REF] Ryman | Protection of intraspecific biodiversity of exploited fishes[END_REF][START_REF] Fraser | Adaptive evolutionary conservation: towards a unified concept for defining conservation units[END_REF]. Overall, debates and lack of consensus in systematics, evolutionary biology, and biological conservation make a ready-to-use population shorting approach unavailable for species domestication/production programs. Moreover, such classifications can highlight populations that are diagnosably distinct from other conspecific population groups but cannot detect the clines of variation that could lead to inter-populational divergences for key trait without clear geographic boundaries (e.g. Heibo et al. 2005;[START_REF] Blanck | Large-scale intraspecific variation in life-history traits of European freshwater fish[END_REF]. Yet, such divergences could be useful for domestication programs.

Therefore, there is a need to establish which approach(es) could be used to efficiently highlight populations that most likely display divergences in key traits prior to their assessment by bioassays. This would ultimately allow selecting wild populations which need to be evaluated in aquaculture conditions to determine which ones are the most interesting for further domestication and production.

We here propose to explore a new approach based on proxies that (i) diverge concomitantly

with key traits and (ii) can be easily studied at large-scale. It is obvious that the best proxy should consist in using genes under selection and coding for key production traits. However, most phenotypic traits are under polygenic control and research identifying quantitative trait loci is still underway [START_REF] Yue | Recent advances of genome mapping and marker-assisted selection in aquaculture[END_REF][START_REF] Robledo | Applications of genotyping by sequencing in aquaculture breeding and genetics[END_REF]; but see for instance research on Salmo salar; e.g. [START_REF] Besnier | Identification of quantitative genetic components of fitness variation in farmed, hybrid and native salmon in the wild[END_REF]. Therefore, alternative proxies of phenotypic differentiation are needed. A first alternative proxy consists in using neutral genes (i.e. locus that does not influence fitness). Indeed, divergences in such genes is widely used to highlight population groups which underwent divergent demographic histories [START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF]. Such groups could have acquired some phenotypic specificities, including in key traits for production (e.g. Lecocq et al. 2016a;Vanina et al. 2019a). Genetic differentiation in neutral markers has previously been suggested as, at least partially, indicative of differentiation in genes coding for quantitative loci [START_REF] Merilä | Comparison of genetic differentiation at marker loci and quantitative traits[END_REF], but see opposite opinion in [START_REF] Holderegger | Adaptive vs neutral genetic diversity: Implications for landscape genetics[END_REF]. Therefore, neutral loci-based genetic distance could be a relevant proxy to discriminate populations that are most likely different in their key traits. A second alternative proxy is based on the degree of divergence of a phenotypic trait [START_REF] Haig | Taxonomic Considerations in Listing Subspecies Under the U.S. Endangered Species Act[END_REF][START_REF] Craig | Revision of the polytypic electric fish Gymnotus carapo (Gymnotiformes, Teleostei), with descriptions of seven subspecies[END_REF] 2017; e.g. behavioral, eco-chemical, or morphological features). Such features can be used to evaluate phenotypic distance that could be linked to genetic divergence [START_REF] Karakousis | Morphological variability among seven populations of brown trout, Salmo trutta L., in Greece[END_REF][START_REF] Joyce | Do taxonomic divisions reflect genetic differentiation? A comparison of morphological and genetic data in Coenonympha tullia (Müller), Satyrinae[END_REF]) and, therefore, potentially highlight divergences in key traits. A third alternative proxy relies on using the degree of habitat divergence to maximize the detection of population groups with different key trait expressions. Indeed, populations inhabiting different environments may be phenotypically divergent [START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF]) because resulting distinct selective pressures act as driving forces for phenotypic differentiation, notably through genetic-based local adaptations [START_REF] Schluter | Ecology and the origin of species[END_REF][START_REF] Myers | Environmental factors predict adaptive phenotypic differentiation within and between two wild Andean tomatoes[END_REF]) that could impact key trait expression. Finally, a fourth alternative could be to consider spatial distance as a relevant proxy. Indeed, given the limited dispersal ability, individuals that are far apart tend to be genetically more divergent than individuals that are spatially close [START_REF] Meirmans | The trouble with isolation by distance[END_REF]. Overall, all these alternative strategies could provide a solution to highlight wild population groups with divergences in key traits for species production. However, the relevance of these alternative proxies is still unsettled because there is no comparison of their efficiency to discriminate populations.

Here, we aim to compare the relevance of different proxies to highlight inter-populational divergences in the expression of traits of interest for aquaculture (TIA) among populations.

First, we evaluate TIA expressions in several fish populations. Second, we perform a retroevaluation of the different proxies on the same fish populations. Finally, we compare the degrees of correlation between alternative proxy-based and TIA-based distance matrices. As a test case, we study a part of the life cycle (larval stage) of seven allopatric populations of the European perch (Perca fluviatilis).

MATERIAL AND METHODS

Species and traits studied

The European perch (Perca fluviatilis) is a freshwater species which is widespread across a diverse range of habitats in Eurasia [START_REF] Stepien | Taxonomy, Distribution, and Evolution of the Percidae[END_REF]. This species started to be produced in the 1990's, mostly in intensive recirculated aquaculture systems (RAS), and presents a high socio-economic value (i.e. food market, recreational interest; Fontaine 2004).

A geographic differentiation was already shown for P. fluviatilis in standardized conditions for TIA related to growth (e.g. Vanina et al. 2019a), development (e.g. Pimakhin and Zak 2014), and behavior (e.g. Toomey et al. 2019).

We evaluated a set of TIA which is related to several biological functions: growth, development, nutrition, and behavior. Growth traits (e.g. growth rate, final growth heterogeneity, initial and final lengths) are widely studied because they are very important for perch larviculture (Kestemont et al. 2015a). Development and nutrition traits (e.g. survival rate, deformity rate, swim bladder inflation rate, yolk sac volume) were also considered because they impact individual fitness and, consequently, larviculture success [START_REF] Woolley | Swimbladder inflation and its implication to the culture of marine finfish larvae[END_REF][START_REF] Boglione | Skeletal anomalies in reared European fish larvae and juveniles. Part 1: Normal and anomalous skeletogenic processes[END_REF]. Finally, behavioral traits were also included in this study since the ability to be successfully produced in intensive conditions depends on aggressiveness [START_REF] Kestemont | Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: Biotic and abiotic influences[END_REF], inter-individual distances (Toomey et al. 2019), and activity [START_REF] Boisclair | The importance of activity in bioenergetics models applied to actively foraging fishes[END_REF].

TIA evaluation in aquaculture standardized conditions

All procedures used in this study were in accordance with national and international guidelines for protection of animal welfare (Directive 2010/63/EU). This study was conducted with the approval Animal Care Committee of Lorraine (CELMA n°66) and the French 119"E). After transportation, 13 to 32 ribbons were incubated at 13 °C at 400 lx (for incubation details, see Toomey et al., 2019). Temperature (13.0 °C ± 0.5 °C) and oxygen rate (9.8 ± 0.7 mg.L -1 ) were monitored every day. Ammonium and nitrite concentrations (lower than 0.05 mg.L -1 ) as well as pH (8.0 ± 0.3) were checked three times a week until hatching.

The experiment, performed in a RAS, started at one day post-hatching (dph) until the end of weaning, at 26 dph. For each population, after hatching, larvae from the different egg ribbons were mixed and transferred to three green (RGB: 137, 172, 118) internal-wall cylindroconical tanks (three replicates per population) at a density of 50 larvae.L -1 at our experimental platform of aquaculture (Unit of Animal Research and Functionality of Animal Products, University of Lorraine, Vandoeuvre-lès-Nancy, France). Temperature was gradually raised to 20 °C (1 °C rise per day). Photoperiod was 12L:12D and light intensity stayed constant during the lighting period at 400 lx at the water surface (with simulation of dawn and dusk for 30 min). Larvae were hand-fed from three days post-hatching, seven times a day, during the illuminated period, every 1h30, with newly hatched Artemia nauplii (Sep-Art, INVE). At 16 dph, weaning started: Artemia ration was diminished by 25% every three days while ration of dry feed (BioMar [Nersac, France], 300 µm until 21 dph, then 500 µm) was increased in the same proportions. After 25 dph, larvae were only fed with dry feed. Tanks were cleaned daily after first-feeding and dead larvae were removed and counted. Oxygen (8.6 ± 1.4 mg.L -1 ) and temperature (20.0 °C ± 0.4 °C) were checked daily. Nitrite and ammonium concentrations (inferior to 0.1 mg.L -1 ), as well as pH (7.8 ± 0.4 mg.L -1 ), were monitored three times a week.

At the end of the experiment, larvae left in each tank were counted and sorted according to the presence/absence of swim bladder inflation (following protocol used in [START_REF] Henderson-Arzapalo | Tricaine used to separate phase-I striped bass with uninflated gas bladders from normal fish[END_REF]); 20 g.L -1 of sea salt and 70 mg.L -1 of MS-222) and skeletal deformities.

Survival rate was calculated using the following formula : Nf*100/(Ni-Ns), in which Nf is the final number of larvae counted at the end of experiment, Ni the initial number of individuals, and Ns the number of larvae sampled along the experiment (i.e. sampling for behavior experiments, see below). In order to evaluation growth traits, 30 larvae per population (i.e. ten larvae per cylindro-conical) were sampled the first and last days of the experiment. After sampling, larvae were euthanized with an overdose of MS-222 and preserved in formalin 4%.

Individuals were measured for total length in ImageJ [START_REF] Schneider | NIH Image to ImageJ: 25 years of image analysis[END_REF]) (± 0.01 mm).

Specific growth rate (SGR) was calculated using the following formula: SGR=100*(ln(Lf)ln(Li))*∆T -1 where Li and Lf are respectively the initial and final length and ∆T the length of experiment. Final growth heterogeneity was calculated in the following way: CV Lf / CV Li where CV is the coefficient of variation (100* standard deviation/mean) and Li and Lf the initial and final length, respectively. Swim bladder inflation rate was calculated in the following way: 100 * (SB+/Nf) with SB+ the number of larvae with swim bladder and Nf the final number of larvae. Deformity rate was evaluated using the following formula: 100*(Nm/Nf) with Nm the number of deformed larvae (visible skeletal deformities) and Nf the final number of larvae. Aggressiveness, including enucleation which is a specific aggressive behavior in P. fluviatilis [START_REF] Jourdan | Influence of daylength on growth, heterogeneity, gonad development, sexual steroid and thyroid levels, and N and P budgets in Perca fluviatilis[END_REF], was evaluated based on the daily examination of dead larvae using the following formula: (Ne + Nt) / Nd where Ne is the number of enucleated larvae, Nt the number of truncated larvae (cannibalism type I; Baras 2013), and Nd the number of dead larvae counted between five and 26 dph (not possible to count dead larvae the first five days but aggressive interactions are reported to start at later stages; [START_REF] Baras | Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions[END_REF]Kestemont et al. 2015a).

The protocol to evaluate inter-individual distances (Buske and Gerlai 2011a) and activity is adapted from [START_REF] Colchen | Temperature modifies activity, inter-individual relationships and group structure in fish[END_REF] and Toomey et al. (2019). All methods were performed in accordance with the relevant guidelines and regulations. In a nutshell, each population was evaluated at 25 and 26 dph. For each population, 90 larvae (i.e. 30 larvae per cylindro-conical tank) were sampled the day before the experiment and transferred to aquaria (58 L; 80 lx) at 20 °C. After one night of acclimatization, populations were tested by groups of ten larvae which were placed in circular arenas (10 lx, 30 cm diameter, 1.5 cm of water depth) and filmed (three arenas tested simultaneously; three replicates per cylindro-conical tank, nine replicates per population). After 30 min acclimatization, the following 30 min were used to evaluate activity and inter-individual distances. and Gerlai 2011a). Analyses were made in ImageJ [START_REF] Schneider | NIH Image to ImageJ: 25 years of image analysis[END_REF]. For each image, coordinates of each individual (using the middle point between the eyes) were noted. This allowed measuring distances between a given individual and the other individuals of the group and these distances were averaged to obtain one value per individual. The mean of values of all group members were averaged per image and the mean between all image values allowed getting a mean value of inter-individual distances per replicate [START_REF] Colchen | Temperature modifies activity, inter-individual relationships and group structure in fish[END_REF].

Regarding activity, one image per second was extracted for six consecutive seconds every five minutes. Distance swam every second for five seconds was calculated and the mean allowed obtaining the distance swam per second for each individual. The mean between individual values allowed getting an activity for each image series. The mean between image series allowed calculating the activity per replicate.

Distance matrix for the different proxies

In the present study, we did not use any phenotypic proxy because morphological and/or behavioral information was not available for all wild perch populations. Moreover, we did not estimate such a proxy on larvae reared in the bioassays because these phenotypic traits can be strongly influenced by the environment (e.g. [START_REF] Svanbäck | Genetic variation and phenotypic plasticity: Causes of morphological and dietary variation in Eurasian perch[END_REF]. Therefore, we only evaluated three proxies: (i) genetic distance, (ii) habitat divergence, and (iii) geographic/hydrologic distance.

Genetic distance proxy

The genetic assessment of the seven populations was performed on 10 individuals per population collected randomly at the end of the experiment. Larvae were stored in 99% ethanol at -20 °C until analyses. Samples were sent to Genoscreen (Lille, France) for DNA isolation, marker amplification, and Sanger sequencing. Three mitochondrial regions were studied (D-loop of control region, cytochrome b, and 16S rRNA; see references for primers in [START_REF] Toomey | Getting off on the right foot: Integration of spatial distribution of genetic variability for aquaculture development and regulations, the European perch case[END_REF] following the protocol available in [START_REF] Toomey | Getting off on the right foot: Integration of spatial distribution of genetic variability for aquaculture development and regulations, the European perch case[END_REF]. Both strands of each PCR product were sequenced. Consensus sequences of mitochondrial regions were computed and edited using CodonCode Aligner 7.1.2 (CodonCode Corporation, Dedham, Massachusetts, USA). There was no uncertainty in the consensus sequences. The P. fluviatilis origin of each sequence was verified using BLAST [START_REF] Zhang | A greedy algorithm for aligning DNA sequences[END_REF]. Sequence alignment was performed in MAFFT (default parameters; [START_REF] Katoh | MAFFT online service: multiple sequence alignment, interactive sequence choice and visualization[END_REF]. Translation to proteins for Cytb was performed in Mesquite 3.20 [START_REF] Maddison | Mesquite: a modular system for evolutionary analysis. Magnhagen C (2006) Risk-taking behavior in foraging young-of-the-year perch varies with population size structure[END_REF]. A tandemly repeated array was identified in D-loop (previously reported in previous P. fluviatilis studies; Nesbø et al. 1998a) and mutations in the repeated array were coded as a single mutational step for further analyses. Mitochondrial markers were concatenated within a single alignment for further analyses using Mesquite. Haplotype sequences were deposited in GenBank (GenBank accession numbers: MN939382 to MN939395). Genetic distances between populations were calculated in R using ɸ ST distance [START_REF] Excoffier | Analysis of molecular variance inferred from metric distances among DNA haplotypes: Application to human mitochondrial DNA restriction data[END_REF]) in SPADS [START_REF] Dellicour | SPADS 1.0: a toolbox to perform spatial analyses on DNA sequence data sets[END_REF].

Habitat divergence proxy

We used 19 bioclimatic data (BIO1 to BIO19) as well as annual mean solar radiation (kJ.m - 2 .day -1 ), annual mean wind speed (m.s -1 ), and annual mean water vapor pressure (kPa) from WorldClim Version2 to assess sampling place environments. We considered these abiotic environmental parameters (at the sampling location) recorded between 1970 and 2000 at a resolution of 10 arc-minutes [START_REF] Fick | WorldClim 2: new 1-km spatial resolution climate surfaces for global land areas[END_REF]. We also used four additional variables: lake area (km 2 ), catchment area (km 2 ), average and maximum depths (m), and altitude (m).

All variables were standardized to zero mean and unit variance due to their different scales of measurement (package "vegan"). A principal component analysis was performed (Supplementary Fig. S2; packages "MASS" and "factoextra") using the Kaiser-Guttman rule to determine the number of axes to retain (here the first four axes representing 98.0 % of the variance). Coordinates for each population replicate were extracted from the first four axes and a distance matrix using the Bray-Curtis distance method was calculated (R package "vegan").

Geographic and hydrologic distance proxies

Geographic distance matrix was set through the calculation of the great-circle distances (i.e.

shortest distance over the earth's surface) according to the « Vincenty (ellipsoid) » method [START_REF] Vincenty | Direct and inverse solutions of geodesics on the ellipsoid with application of nested equations[END_REF]) implemented in the R package "geosphere". Because this geographic distance is a priori not relevant for fish species, we also estimated an hydrologic distance using an algorithm based on circuit theory and implemented in the program Circuitscape [START_REF] Shah | Circuitscape: a tool for landscape ecology[END_REF]. Rivers and lakes shapefiles were respectively extracted from the Catchment Characterization and Modelling river and catchment database v2 [START_REF] Vogt | A pan-European River and Catchment Database. Ctachment characterisation and modelling[END_REF] and HydroSHEDS [START_REF] Lehner | New Global Hydrography Derived From Spaceborne Elevation Data[END_REF]) and from Natural Earth (www.naturalearthdata.com)

databases, and jointly rasterized on a geo-referenced grid with a resolution of 0.5 arcmin.

Specifically, we assigned a value of "1" to terrestrial raster cells that were not crossed by a river or occupied by a lake and a value of "100" for terrestrial raster cells crossed by a river or occupied by a lake. We then used the program Circuitscape [START_REF] Shah | Circuitscape: a tool for landscape ecology[END_REF] to compute the pairwise electric resistance between all pairs of populations and this, by treating the resulting raster as a conductance grid. One of the advantages of the Circuitscape algorithm is that it takes into account the contribution of several potential pathways to compute pairwise distances (resistances) between locations. We used these pairwise electric resistances as an estimation of pairwise hydrologic distances between populations.

Relevance of the different proxies

In order to create a trait-by-trait distance matrix, we first checked the statistical differentiation (p-value<0.05) of phenotypic traits between populations: we tested normality of distribution and homogeneity of variances using a Shapiro-Wilk test and a Levene test, respectively (R package "lawstat"). When assumptions were not respected, data were log-transformed. To check the influence of the cylindro-conical tank on results, we compared linear (phenotypic traits as fixed factors, no random factor) and linear mixed models (cylindro-conical tanks as random factor and phenotypic traits as fixed factors; R package "lmer") using the corrected Akaike Information Criterion (AICc; R package "qpcR"). For most traits, there was no significant influence of the cylindro-conical tank on the model. Therefore, we used one-way analyses of variance (ANOVA F-test), followed by Tukey post hoc tests (R package "stats"), to evaluate differences between populations. When the effect of the cylindro-conical tank was significant, we performed the ANOVA on the linear mixed model and estimated marginal means were calculated (R package "emmeans"). Regarding aggressive rate and activity, assumptions were not met despite log-transformation. Thus, Kruskal-Wallis H tests and Dunn post hoc test (R package "PMCMR") were used. Traits presenting no significant differentiation between populations were excluded from further analyses.

A trait-by-trait distance matrix was created using the Euclidean method (R package "vegan", three replicates per population). All distance matrices are available in Figshare (doi:

10.6084/m9.figshare.11407128). We performed multivariate analyses using multi-regression on distance matrices (1000 permutations) coupled with commonality analyses (further referred as "MRDM-CA") using R packages "ecodist" and "yhat". For these analyses, all proxy-based distance matrices were preliminary standardized. The multi-regression on distance matrices (MRDM) analysis allows estimating the Pearson correlation coefficient r (i.e. direct effect of the proxy on the response variable, irrespectively from the influence of other proxies) and beta weights (i.e total effect of the proxy on the response variable, taking into account the contribution of other proxies). The commonality analysis (CA) is a detailed variance-partitioning procedure which allows taking into consideration collinearity between proxies [START_REF] Prunier | Multicollinearity in spatial genetics: separating the wheat from the chaff using commonality analyses[END_REF]. This analysis estimates the unique ("U"; amount of variance in the TIA accounted for by each single proxy) and common ("C"; variance jointly explained by several proxies) contributions of each proxy. After the first round of MRDM-CA, total suppressors were identified and discarded because they can be responsible for artefactual relationships among variables. This can allow purifying the relationships between the remaining proxies and the response variable (i.e. in our case the TIA-based distance matrices; [START_REF] Prunier | Multicollinearity in spatial genetics: separating the wheat from the chaff using commonality analyses[END_REF]. Successive MRDM-CA were performed until all suppressors were removed. A proxy was considered as a total suppressor when unique contribution is counterbalanced by its (negative) common contribution (classical suppression) and/or when regression and correlation coefficients are of opposite signs (cross-over suppression; [START_REF] Prunier | Multicollinearity in spatial genetics: separating the wheat from the chaff using commonality analyses[END_REF][START_REF] Dellicour | Distribution and predictors of wing shape and size variability in three sister species of solitary bees[END_REF]). In addition, we investigated correlations between traitbased and proxy-based distance matrices using Mantel tests in R (R package "vegan"; 9,999 permutations). Four Mantel tests were performed for each TIA: (i) ɸ ST genetic distance vs TIA-based distance matrix, (ii) habitat divergence vs TIA-based distance matrix, (iii) geographic distance vs TIA-based distance matrix, and (iv) hydrologic distance vs TIA-based distance matrix.

RESULTS

TIA evaluation in aquaculture standardized conditions

There was no statistically significant difference between populations for aggressive rate (K=8.85, df=6, p-value=0.18) and length heterogeneity (F (6,14) ; where 6 corresponds to the first degree of liberty [number of populations-1] and 14 to the second degree of liberty [total number of replicates-number of populations]=0.86, p-value=0.55).

A significant statistical differentiation between populations was found for survival rate (F (6,14) =9.45, p-value=5.75x10 -4 ), swim bladder inflation rate (F (6,14) =22. 73, p-value=6.79x10 - 6 ), deformity rate (F (6,14) =11.29, p-value=1.12x10 -4 ), specific growth rate (F (6,14) =8.64, p-value=4.69x10 -4 ), length at hatching (F (6,14) =17.33, p-value=2.85x10 -5 ), final length (F (6,14) =8. 35, p-value=5.58x10 -4 ), yolk sac volume (F (6,14) =32.95, p-value=1.77x10 -7 ), activity (K=20.24, df=6, p-value=0.003), and inter-individual distances (F (6,56) =5.59, p-value=1.35x10 -4 ). All inter-populational comparisons are available in Supplementary Figure S3.

Correlation degrees of the different proxies with the TIA-based matrices

The series of successive MRDM-CA allowed identifying several suppressors. Therefore, some TIAs are only correlated with a single proxy remaining after suppressors' removal (Table 1). Overall, MRDM-CA results indicate that significant global MRDM R 2 are relatively high (>10%), and that all TIA are associated with a positive and significant correlation with a unique proxy-based matrix (when considering only proxies for which the CA unique contribution U > 5 %), except for final length which is not correlated with any proxy (Table 1). The geographic distance proxy is not correlated with any TIA-based distance matrix while the genetic distance proxy is the one which is correlated to the highest number of TIA-based distances matrices. However, none of the proxy is showing a systematic significant contribution with all TIA. Considering genetic, habitat, and hydrologic distance proxies, all TIA are correlated with at least one of the proxies, except for final length (Table 1).

Regarding Mantel tests, results are available in Supplementary Table S1 and are globally congruent with MRDM-CA analyses. Overall, for each TIA, the proxy which was the most correlated in the Mantel test is the one which is significant in the MRDM-CA analysis.

DISCUSSION

Assessment of TIA expression differentiation

Because we used a common garden experiment, we assumed that observed differentiations in the TIA expression have a genetic basis and are not due to phenotypic plasticity.

Nevertheless, we used individuals sampled at the egg stage in the wild. Therefore, we cannot rule out that a part of TIA expression divergences is shaped by transgenerational effects or phenotypic plasticity [START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF][START_REF] Youngson | Transgenerational epigenetic effects[END_REF]. However, we argue that our experimental design has minimized as far as possible such potential biases.

Another potential bias relies on the variable number of egg ribbons used between populations which could have influenced TIA results. However, we minimized the female specificity bias by taking a large number of egg ribbons for each population.

One proxy is not enough

We showed that no single proxy-based distance matrix is correlated with all TIA-based distance matrices. We found four significant correlations for genetic distance and two significant correlations for hydrologic distance and habitat divergence when we compared them with TIA-based distance matrices (Table 1). We also observed that each TIA is only significantly correlated with one proxy (Table 1).

Since inter-populational divergences can be shaped by ( i The habitat divergence proxy can theoretically overcome limitations of spatial disjunction proxies because it could highlight specific selective pressures at any geographic scale and, thus, inter-populational divergences (e.g. [START_REF] Jørgensen | Marine landscapes and population genetic structure of herring (Clupea harengus L.) in the Baltic Sea[END_REF][START_REF] Langerhans | Complex phenotype-environment associations revealed in an East African cyprinid[END_REF]).

Nevertheless, we observed only few significant correlations between TIA and habitat divergence. This can be explained because the habitat divergence proxy assessment most likely fails to highlight populations undergoing different selective pressures. First, the selection of relevant variables involved in local selective pressure is still hard to achieve.

Indeed, the importance of environmental variables on population evolution is species-specific (and unsettled for P. fluviatilis) and cannot be known without long and difficult bioassays (e.g. [START_REF] Chabot | Environmental hypoxia as a metabolic constraint on fish: The case of Atlantic cod, Gadus morhua[END_REF]. Second, relevant environmental data on freshwater ecosystems are unevenly available for the different regions of the world. For instance, in our study, the worldwide databases of freshwater environmental variables (e.g. [START_REF] Domisch | Near-global freshwater-specific environmental variables for biodiversity analyses in 1 km resolution[END_REF] do not cover the whole studied sampling area. This led us to use terrestrial data in order to extrapolate aquatic environment characteristics (see similar strategy in [START_REF] Knouft | Climate and local abundance in freshwater fishes[END_REF][START_REF] Sherwood | Predicting the range of a regionally threatened, benthic fish using species distribution models and field surveys[END_REF], although it could potentially blur studied lake specificities.

Optimally, analyses should be performed using data specific to lakes (e.g. lake physicochemical parameters, feeding base) to improve the use of this proxy but the unavailability of sufficient data limits this strategy. Beside these difficulties, the habitat divergence proxy assessment can fail because extensive gene flow from adjacent regions can limit local adaptations [START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF]) and, thus, minimize TIA expression divergences, even if specific environmental pressure occurs locally.

One could expect that the genetic distance proxy would be the most efficient to highlight populations with divergent TIA expressions. Indeed, it could detect populations with genetic divergences due to gene flow limitation/disruption triggered by spatial/hydrologic distance (i.e. isolation by distance), geographic barriers (i.e. geographic isolation), ecological barriers, or behavioral specificity (e.g. natal homing behavior). However, our results highlight that not all TIA are correlated with the genetic distance proxy. Moreover, some traits which are not correlated with the genetic distance proxy are correlated with another proxy. To explain the absence of correlation of some TIA with the genetic distance proxy, it could be hypothesized that populations could have diverged recently, implying that few divergences in neutral markers had time to appear [START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF][START_REF] Cruaud | Empirical assessment of RAD sequencing for interspecific phylogeny[END_REF].

How to better catch the divergence: a multi-proxy strategy

Because there is no proxy-based distance correlated with all TIA-based distances, highlighting populations that likely display TIA expression divergences should be based on the use of several proxies. Genetic distance and habitat divergence proxies are theoretically complementary to maximize the detection of such populations. On the one hand, the genetic distance proxy is relevant to highlight divergence by distance or populations with divergent demographic histories while the habitat divergence proxy can reflect local adaptations which are not (already) visible in neutral markers. On the other hand, populations occurring in similar habitats can display phenotypic divergences, including in TIA. Thus, the use of these two proxies allows taking into consideration both gene flow disruption/limitation and local adaptation to specific selective pressures. However, these proxies can be sometimes misleading due to their intrinsic limitations (see before), particularly the habitat divergence proxy (unless performing the analysis with more relevant lake variables). One way to mitigate their limitations relies on the combination of these two proxies with the hydrologic distance proxy (according to our results, the geographic distance proxy can be beneficially replaced by hydrologic distance proxy, which is more relevant for aquatic species and is the only one correlated to some TIA-based distance matrices). The hydrologic distance proxy could be correlated with both phenotypic differentiation by distance and local adaptations between distant populations. Moreover, the hydrologic distance proxy is correlated in our study with two TIA which are not correlated neither with genetic distance or habitat divergence proxies.

Even though its calculation might be time and system memory-consuming, it requires no specific information except for geographic coordinates which makes it simple and useable in all scenarios. Here, we promote the use of a multi-proxy approach to pinpoint a population or population group to be assessed for TIA expression divergences. Another potential alternative would rely on ranking the TIA since not all TIA have the same importance to stakeholders.

This strategy would consist in choosing the proxy which is correlated to the most important TIA (e.g. growth rate and survival rate; Kestemont et al. 2015a). However, this strategy is not optimal since a successful domestication process requires the favorable expression of several traits involved in various biological functions.

Regarding the multi-proxy strategy, it is likely that the different proxies drive to divergent conclusions regarding which populations should be considered. Moreover, all populations cannot be evaluated in bioassays if many populations are considered and if they are all somewhat divergent for one or more proxies. Indeed, the potential over-estimation of populations or population groups that could be potentially TIA-divergent (Padial et al. 2010) is the main pitfall of multi-proxy based assessment. Therefore, prioritization procedures should be developed. For instance, a ranking of population/population group pairs according to their degree of divergences in each proxy could be performed. Then, bioassay effort could be focused on the most distant pair(s) for each proxy considered, as well as eventually population pair(s) which are distant across all proxies (e.g. high average rank across proxies) could be a solution. It would maximize the probability to highlight population with TIA expression divergences. The number of pairs that will be effectively evaluated in bioassays will depend on availability of experimental facilities as well as financial and human means.

Nevertheless, any alternative assessment approach should be tested on other species in order to extend its relevance at global scale.

inter-population differentiation and to verify the potential maternal effects on offspring performance (e.g. as performed for instance in Glover et al. 2003). Maternal effects, due to differences between female states (e.g. age, feeding regime, and nutritional reserves, stress), can have an impact on the fitness of the offspring. They have already been shown for many species such as P. flavescens [START_REF] Heyer | Maternal effects as a recruitment mechanism in Lake Michigan yellow perch (Perca flavescens)[END_REF], Oncorhynchus tshawytscha (Actinopterygii, Salmoniformes, Salmonidae; [START_REF] Heath | Maternal effects on offspring size: variation through early development of Chinook salmon[END_REF], or Amphiprion melanopus (Actinopterygii, Perciformes, Pomacentridae; [START_REF] Green | Maternal and paternal effects determine size, growth and performance in larvae of a tropical reef fish[END_REF]. However, rearing several family lines and several populations is ultimately not pragmatic and feasible (i.e. it requires to significantly increase the workload). An alternative consists in performing factorial mating (crossing all males and females) which allows estimating maternal effects, but this is a costly approach [START_REF] Dupont-Nivet | Optimization of factorial mating designs for inference on heritability in fish species[END_REF]. As an alternative, in this work, individuals originating from 13 to 32 egg ribbons were used (Table 12). It can be argued that the higher the number of egg ribbons is, the more the intra-population variability was considered, and the more maternal effects were minimized. However, an uncertainty remains regarding the true contribution of each female to the experimental larval population. Indeed, larvae were mixed after hatching to constitute experimental groups from the pool of larvae, but strong mortalities occurred in the first days post-hatching and during the transition between endogenous and exogenous feeding. It cannot be assessed that all ribbons contributed to the larvae which survived. This would require genotyping both parents and offspring and performing parental assessment (as made in [START_REF] Borrell | Assessing the spawning season in common dentex (Dentex dentex) using microsatellites[END_REF]Król et al. 2015), which was not possible in this study, having no family background information about the broodstock. In addition, regarding sampling, egg ribbons should be ideally collected at several spawning locations within a site to avoid sampling uniquely siblings, but this was not possible for all populations in this work.

Despite these biases, the demonstration of inter-populational differentiation is more robust when using a high number of ribbons since it allows (i) taking into account intra-population variability, (ii) limiting the risk of sampling only sub-optimal phenotypes or siblings, and (iii) limiting the female specificity bias.

The variable number of ribbons between populations (Table 12) could have influenced the results. Yet, this step was not possible to standardize because of the (i) uncertainty of the number of ribbons which could be collected before the sampling season, (ii) the temporal shift between spawning seasons which made adjustments between populations impossible, and (iii) the size of the ribbons which were smaller for northern populations implying a higher number of ribbons required to have a sufficient number of larvae. However, no consistency was found between the number of ribbons and performances (e.g. the highest number of ribbons does not correspond to the population performing the best). Therefore, the variable number of ribbons does not seem to have significantly influenced results. [START_REF] Alix | An alternative developmental table to describe nonmodel fish species embryogenesis: application to the description of the Eurasian perch (Perca fluviatilis L. 1758) development[END_REF] were excluded from the experiment during the incubation phase. However, this might not be sufficient to standardize the use of initial biological material. In order to ensure the homogeneity of this incubation phase, the initial state of eggs could be checked using biochemical parameters (e.g. fatty acid composition) to correctly assess egg quality. However, relevant indicators of perch egg quality are still debated [START_REF] Schaerlinger | Evaluation and improvements of egg and larval quality in percid fishes[END_REF]. A study suggested a relationship between the perch female length and the egg and fry quality [START_REF] Olin | Importance of maternal size on the reproductive success of perch, Perca fluviatilis, in small forest lakes: Implications for fisheries management[END_REF]). However, this relationship was demonstrated in one specific lake and we did not have information about females since the relationship between female length and egg ribbons width is not valid in all lakes [START_REF] Gillet | Influence of temperature and size of females on the timing of spawning of perch, Perca fluviatilis, in Lake Geneva from 1984 to 1993[END_REF][START_REF] Huss | The origin and development of individual size variation in early pelagic stages of fish[END_REF][START_REF] Olin | Importance of maternal size on the reproductive success of perch, Perca fluviatilis, in small forest lakes: Implications for fisheries management[END_REF].

Finally, egg ribbons were only sampled from lakes in this study. Indeed, it was easier to collect biological material from lakes compared to rivers and more importantly the lake morphotype is the one required by consumers. Yet, populations from rivers and estuaries might have shown different performances. However, (i) environmental conditions between lakes are also quite different and (ii) according to the phylogeographic study, populations belonging to different habitats (lakes, rivers, estuaries) are present within a same PU. Yet, it would be interesting to sample egg ribbons from rivers and brackish waters to assess the importance of local factors such as water velocity or salinity. However, this would imply working at smaller scale than the one used in this work.

Differential pre-experimental conditions

Another possible limitation might have been the transport time which was different between populations and could have triggered negative effects (Table 12). However, the longest transportation time (Finnish populations) does not correspond to the population with the lowest performance. In addition, all ribbons were transported before the eyed stage which is the most sensitive stage. Thus, the impact of transport seems minimal in our experiment.

Potential bias in the experimental set up

In order to highlight genetically-based differentiations, common garden experiments are required. However, it was not possible to perform a "true" common-garden experiment (i.e.

larvae from the different populations in the same tank) since (i) it is not possible to tag newly hatched larvae and (ii) there is a temporal shift in the spawning seasons and therefore, at a given date, larvae from different populations had different age and length. Thus, a part of the variability between populations could be due to micro-variations between tanks (Sae- [START_REF] Lim | A review of genotype-by-environment interaction and micro-environmental sensitivity in aquaculture species[END_REF]). However, three replicates were performed for each population which allowed limiting this bias and the cylindro-conical tank was included as a random effect in statistical analyses.

Another potential bias corresponds to the comparison of populations relatively to the age posthatching. Indeed, all parameters were evaluated after important production stages (weaning, end of larviculture) at precise dates post-hatching. However, different populations might present different developmental speeds (i.e. intraspecific heterochrony; [START_REF] Kawajiri | Heterochronic differences in fin development between latitudinal populations of the medaka Oryzias latipes (Actinopterygii: Adrianichthyidae)[END_REF][START_REF] Jong | Polymorphism in developmental timing: Intraspecific heterochrony in a Lake Victoria cichlid[END_REF]. By the time of the experiment, a development table was only available from fertilization until exogenous feeding [START_REF] Alix | An alternative developmental table to describe nonmodel fish species embryogenesis: application to the description of the Eurasian perch (Perca fluviatilis L. 1758) development[END_REF]. However, another development table was published in 2019 and covers larval and juvenile stages [START_REF] Kupren | Early development and allometric growth in hatchery-reared Eurasian perch, Perca fluviatilis L[END_REF]. This development table (Figure 9) could help in the future to better standardize experiments and to compare populations at development stages rather than specific days post-hatching. Through the analysis of pictures taken at different time steps for the different populations, the shift of development could be tested. Indeed, at given post-hatching ages, inter-population differences in yolk sac resorption, fin development, fin rays apparition, or swim bladder inflation would confirm/refute developmental shifts. Finally, because of differences in spawning season timing, trials did not occur at the same time between perch populations. However, same exact protocols were used between populations and trials overlapped between all populations within each year. The differential years of experiment could have influenced results, but the exact same protocol was used between 2018 and 2019.

Which implications for European perch larviculture?

We validated that geographic differentiation exists in European perch for many key traits (chapters one, four, and five), both at population and PU levels (Table 13; validation of hypothesis H1). These results can be useful for European perch larviculture, particularly considering key traits for which the difference delta is quite high between populations/PU such as for survival rate, swim bladder inflation rate, deformity rate, or final weight (Table 13). Differentiation in European perch key traits was already previously shown for several key traits [START_REF] Mandiki | Effects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions[END_REF][START_REF] Pimakhin | Effect of body size on swim bladder inflation in intensively cultured Eurasian perch larvae from different locations[END_REF]Vanina et al. 2019a, b), but the

Reminder of work hypotheses

H1: There is a geographic differentiation in Perca fluviatilis for key traits.

H2:

There are units with high potential for aquaculture within species.

differences in age post-hatching evaluations and rearing conditions makes comparisons with our results difficult.

The fourth chapter allowed validating the hypothesis H2 since there are divergent potentials for aquaculture (here limited to larviculture) between prospective units. Considering all results across the different chapters, Lake Balaton/Danube group was shown as the population/PU with the highest aquaculture potential. Unfortunately, Lake Balaton was the only population representative of the Danube group. Therefore, it was not possible to verify the within-Danube group differentiation. The lowest potential for aquaculture was highlighted

for Lake Geneva at the population level. This is consistent with a hypothesis raised by Ben Khadher (2015). In European perch farmed stocks studied, Lake Geneva individuals were supposedly at the origin of the founder stocks [START_REF] Khadher | Genetic characterization and relatedness of wild and farmed Eurasian perch (Perca fluviatilis): Possible implications for aquaculture practices[END_REF]). Yet, they were poorly represented in farmed stocks, in which several probable introductions of individuals from different geographic origins occurred. Authors suggested as a plausible explanation a poor performance of individuals from Lake Geneva in aquaculture conditions compared to other allopatric populations [START_REF] Khadher | Genetic characterization and relatedness of wild and farmed Eurasian perch (Perca fluviatilis): Possible implications for aquaculture practices[END_REF]. Differences in performances could have substantial impacts for perch farms. Considering a specific example with survival rate which is a major bottleneck in Percid larviculture (Policar et al. 2019), there is a high differentiation between Lakes Geneva and Balaton. On the base of price quotations, selling cost of European perch larvae at 3g is about 10-30 cents per larvae. Looking at results obtained at the end of phase I (phase with the highest mortalities), there is a loss of about 212 euros per replicate worth of sale for Lake Geneva compared to Lake Balaton (not considering variable costs). Rearing more larvae (in the limit of the company capacities) is going to increase variable costs (e.g. feed) but fixed costs will be the same (e.g. equipment, oxygen, salaries). The larvae are less than 3g at 26 dph but this still gives an idea about the impact of survival differences on farm revenues. Improving survival could allow decreasing the overall production cost. This estimation is made for rearing densities used in this work, but fish farmers use higher densities and larger tanks. Therefore, there can be a substantial financial impact in the choice of the founder population. Overall, these results are first insights which could be helpful for P. fluviatilis larviculture, but these results are specific to our RAS system.

Traits relevant for European perch larviculture were evaluated but some traits listed in the second chapter were not included in the following chapters. Firstly, regarding the category 1, timing for exogenous feeding was not evaluated since the feeding protocol was the same for all populations (i.e. fixed domestication system). Other traits were not included because of method evaluation limitations. In this way, age/size at cannibalism onset were not included in the fourth and fifth chapters. We did get this information for five populations but it relied on daily 10-minute observations, which triggered several biases: (i) observers were different between 2018 and 2019, (ii) observations were made after first feeding but cannibalism might occur at other moments through the day, and (iii) the presence of the observer might disturb the behavior of larvae. We suggest that a new protocol should be developed to evaluate this trait (e.g. camera above the tank with a lower water depth). However, the global aggressiveness rate, which includes cannibalism rate (I and II) and enucleation, was assessed which allowed to evaluate mortalities potentially due to aggressiveness. This also illustrates the global difficulty tied to the life-stage studied. Working on larvae is not easy because of the small size (Figure 10) of individuals and makes the evaluation of some traits difficult. For instance, respecting precise initial densities and following daily mortalities requires counting individuals and because larvae are small, some errors in counting are inevitable. However, these biases are the same for all populations. The rest of the life cycle needs to be performed in order to evaluate other traits from category one (see Table 1 in the second chapter). Moreover, the evaluation over the full life cycle is required to assess if the best populations/PU for larviculture are also the best for on growing and reproduction. Regarding category 2, related to larviculture, the acceptance of artificial diets and the resistance to sub-lethal stress were not evaluated directly, but survival rate is an integrative trait which, among other factors, reflects mortality subsequent to non-acceptance of dry feed and stress. Yet, an experiment to specifically evaluate resistance to stress (see for instance protocol in [START_REF] Colson | Egg cortisol exposure enhances fearfulness in larvae and juvenile rainbow trout[END_REF] and diseases (e.g. protocol in [START_REF] Giri | Potential probiotic Lactobacillus plantarum VSG3 improves the growth, immunity, and disease resistance of tropical freshwater fish, Labeo rohita[END_REF]) would allow to better evaluate the aquaculture potential. Traits relative to categories three and four still need to be evaluated and require the development of specific methodologies such as the acceptance of alternative feeds (e.g. [START_REF] Fountoulaki | Fish oil substitution by vegetable oils in commercial diets for gilthead sea bream (Sparus aurata L.); effects on growth performance, flesh quality and fillet fatty acid profile. Recovery of fatty acid profiles by a fish oil finishing diet under fluctuating water temperatures[END_REF][START_REF] Gisbert | Weaning wild flathead grey mullet (Mugil cephalus) fry with diets with different levels of fish meal substitution[END_REF]; see first experiment on P. fluviatilis juveniles with linseed oil replacement : Geay et al. 2015a;Geay et al. 2015b), which is partly determined by genetic components [START_REF] Blonk | Genetic improvement of percids[END_REF]. B. The three-step integrative method: limits of the approach and potential improvements 1.

Step 1: Classification

Establishing a phylogeographic classification

This first step is essential and is aimed at classifying wild populations in order to (i) restrict the range of possibilities and (ii) identify biological units which are likely to present differentiations in key traits for domestication and production. We relied for this first step on a phylogeographic classification based on neutral markers since there can be a congruence in the wild between phenotypic differentiation and phylogeographic structure due to long periods of neutral and selective evolution of lineages [START_REF] Zhao | Life history variation parallels phylogeographical patterns in North American walleye (Sander vitreus) populations[END_REF][START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF].

Indeed, groups of populations presenting divergent demographic histories could have acquired, notably through local adaptations or random phenomena, some phenotypic specificities. In this way, populations inhabiting divergent environments and/or exchanging few or no migrants (i.e. low gene flow) may differ genetically and display phenotypic differences due to local selective pressures [START_REF] Mayr | Animal species and evolution[END_REF][START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF][START_REF] Kawecki | Conceptual issues in local adaptation[END_REF][START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF]. The degree of genetic differentiation depends on population history (range expansion, founder effect, secondary contact), population size, time since divergence, and gene flow [START_REF] Hauser | Paradigm shifts in marine fisheries genetics: ugly hypotheses slain by beautiful facts[END_REF]. Using mitochondrial markers, we provided a large-scale genetic structure. Congruent results were observed with microsatellites

Take home message

There are several experimental biases which can potentially influence results obtained on P. fluviatilis first life stages. However, numerous of theses biases are inevitable and were minimized as much as possible. Some alternative solutions were proposed in this section, but the pragmatism of the methods used for each step of the integrative approach remains a priority. Despite these experimental biases, a geographic differentiation was highlighted for numerous key traits for larviculture at the population and PU levels for P. fluviatilis first life stages. This is translated by differential potentials for aquaculture. Therefore, the two initial hypotheses of this work were validated. This work is a first step towards a facilitation of domestication and subsequent production of P. fluviatilis through the consideration of geographic differentiation. Further studied are needed to assess performances over the full life cycle and for traits belonging to other categories.

at smaller-scale with a subdivision of the main prospective units, despite the low number of samples used for this marker type. The genetic differentiation can be high at even smaller scales, such as within the course of a river or within a lake, since differentiations in lifehistory and habitats can be strong (e.g. [START_REF] Behrmann-Godel | Postglacial colonization shows evidence for sympatric population splitting of Eurasian perch (Perca fluviatilis L.) in Lake Constance[END_REF][START_REF] Erkinaro | Life-history and habitat features influence the withinriver genetic structure of Atlantic salmon[END_REF][START_REF] Bergek | Population differentiation in perch Perca fluviatilis: environmental effects on gene flow?[END_REF][START_REF] Hughes | Extreme genetic structure in a small-bodied freshwater fish, the purple spotted gudgeon, Mogurnda adspersa (Eleotridae)[END_REF]). However, this study is aimed at being pragmatic and at highlighting a large-scale genetic structure. By considering the mitochondrial genetic structure, we increased chances of detecting differentiations in key traits which can be preserved across generations. The establishment of such a classification is an undeniable advantage since it is not possible to compare all wild populations in the second step and comparing random populations is not an optimal approach.

Limitations of the phylogeographic classification

Establishing a phylogeographic classification might be easier for freshwater fishes due to the presence of physical barriers compared to marine fishes where genetic differentiations are often lower because of greater dispersal [START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF][START_REF] Ward | The importance of identifying spatial population structure in restocking and stock enhancement programs[END_REF][START_REF] Hauser | Paradigm shifts in marine fisheries genetics: ugly hypotheses slain by beautiful facts[END_REF][START_REF] Nielsen | Genomic signatures of local directional selection in a high gene flow marine organism; the Atlantic cod (Gadus morhua)[END_REF]. For instance, identifying a large-scale genetic structure might be challenging for the European eel (Anguilla anguilla L.) because of a low genetic differentiation highlighted at smaller geographic scales [START_REF] Hoffmann | Analysis of the genetic structure of European eel (Anguilla anguilla) using microsatellite DNA and mtDNA markers[END_REF][START_REF] Dannewitz | Panmixia in the European eel: A matter of time[END_REF][START_REF] Palm | Panmixia in European eel revisited: No genetic difference between maturing adults from southern and northern Europe[END_REF][START_REF] Ragauskas | Analysis of the genetic structure of the European eel Anguilla anguilla using the mtDNA D-loop region molecular marker[END_REF]). However, a strong genetic structure was highlighted for plenty of other species (e.g. [START_REF] Durand | Phylogeography and postglacial dispersion of the chub (Leuciscus cephalus) in Europe[END_REF][START_REF] Kotlík | Phylogeography of the barbel (Barbus barbus) assessed by mitochondrial DNA variation[END_REF][START_REF] Van Houdt | Phylogenetic relationships among Palearctic and Nearctic burbot (Lota lota): Pleistocene extinctions and recolonization[END_REF][START_REF] Gum | Mitochondrial and nuclear DNA phylogeography of European grayling (Thymallus thymallus): evidence for secondary contact zones in central Europe[END_REF][START_REF] Østbye | Evolutionary history of the European whitefish Coregonus lavaretus (L.) species complex as inferred from mtDNA phylogeography and gill-raker numbers[END_REF][START_REF] Seifertová | Multiple Pleistocene refugia and post-glacial colonization in the European chub (Squalius cephalus) revealed by combined use of nuclear and mitochondrial markers[END_REF][START_REF] Salmenkova | New view on the population genetic structure of marine fish[END_REF][START_REF] Jamaluddin | Genetic variation, demographic history and phylogeography of tire track eel, Mastacembelus favus (Synbranchiformes: Mastacembelidae) in Southeast Asia[END_REF]. Therefore, the difficulty of this first step is species dependent and since phylogeographic studies are widely performed [START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF], the classification might be available in literature when considering a new candidate species, providing that this classification was established based on a multi-marker approach and at large-scale. However, genetic techniques evolving fast, it might drive phylogeographic structures previously established to be quickly obsolete.

The usefulness of the phylogeographic classification might be limited for species for which translocations are performed at the time of the three-step evaluation. Indeed, some new candidate species for domestication could have an interest for recreational fisheries or could be submitted to enhancement programs to restore natural stocks (for conservation or exploitation purposes). In these scenarios, there might be introduction of exogenous individuals in some targeted sampling sites between the first and second steps. This leads to the risk to sample for bioassays individuals which are not representative of the prospective unit. In addition, if translocations are performed after the three-step approach, it can be an issue when constituting a stock using the results of the three-step method. Indeed, when targeting a unit with high potential for aquaculture, there is a risk of sampling fish which will display different specificities than those highlighted during the three-step assessment.

Therefore, sites in which translocations are performed at the time of the evaluation or after should be avoided for the sampling step of bioassays or farm stock constitution. Finally, translocations can have greater impacts when performed widely across the distribution range.

Indeed, in extreme cases, it could also present the establishment of an intraspecific classification because of a genetic homogenization across the distribution range [START_REF] Ryman | Protection of intraspecific biodiversity of exploited fishes[END_REF][START_REF] Champagnon | Conspecifics can be aliens too: A review of effects of restocking practices in vertebrates[END_REF]. In this extreme case, applying the three-step approach would be limited.

The fifth chapter highlighted that the genetic proxy does not allow reflecting differentiation for all key traits. The use of neutral markers has been hypothesized as the main explanation about the lack of correlation between some trait distance matrices and the genetic distance matrix. Even though genetic differentiation can occur quickly (i.e. decades) when selective pressures and/or genetic drift are strong, recent adaptations might not be visible in neutral markers [START_REF] Ballentine | Common garden experiment reveals genetic control of phenotypic divergence between swamp sparrow subspecies that lack divergence in neutral genotypes[END_REF][START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF]. Therefore, neutral divergence can be a poor predictor of adaptive trait variation [START_REF] Leinonen | Comparative studies of quantitative trait and neutral marker divergence: a meta-analysis[END_REF]).

1.3 Genetic alternatives to the phylogeographic proxy?

One could state that genetic differentiation could have been replaced by genetic heterozygosity. Indeed, a relationship was suggested between the level of heterozygosity and fitness (e.g. [START_REF] Koehn | Genetic heterozygosity and growth rate in Mytilus edulis[END_REF][START_REF] Hayes | Use of molecular markers to maximise diversity of founder populations for aquaculture breeding programs[END_REF]). However, this relationship varies among and within species and many studies show the absence of a correlation [START_REF] Appleyard | Individual heterozygosity levels and relative growth performance in Oreochromis niloticus (L.) cultured under Fijian conditions[END_REF]Wang et al. 2002 and references within). Although there is an overall agreement that inbreeding can lead to a decrease in biological performance (but see potential increase of natural selection effectiveness [i.e. genetic purging]; García-Dorado 2015) under culture conditions, no correlation can be made between genetic heterozygosity and performance [START_REF] Vogt | A pan-European River and Catchment Database. Ctachment characterisation and modelling[END_REF][START_REF] Vandeputte | Quelle gestion génétique de la domestication chez les poissons?[END_REF].

The use of adaptive markers could be an interesting alternative since they can provide better estimates of differentiation caused by ecological gradients [START_REF] Conner | A primer of ecological genetics[END_REF][START_REF] Holderegger | Adaptive vs neutral genetic diversity: Implications for landscape genetics[END_REF]. Approaches have been developed to infer the genetic basis of adaptive phenotypic divergence between populations using multilocus mapping approaches such as quantitative trait loci (QTL) mapping [START_REF] Eknath | Genetic improvement of farmed tilapias: the growth performance of eight strains of Oreochromis niloticus tested in different farm environments[END_REF][START_REF] Storz | INVITED REVIEW: Using genome scans of DNA polymorphism to infer adaptive population divergence[END_REF]). However, this approach requires comparisons of populations in controlled conditions to identify adequate QTL and genetic underpinnings of many quantitative traits are still unknown [START_REF] Holderegger | Adaptive vs neutral genetic diversity: Implications for landscape genetics[END_REF][START_REF] Merilä | Climate change, adaptation, and phenotypic plasticity: the problem and the evidence[END_REF]). An alternative approach to detect locusspecific signature of directional selection without screening phenotypic variation relies on genome scans approaches [START_REF] Storz | INVITED REVIEW: Using genome scans of DNA polymorphism to infer adaptive population divergence[END_REF]. Indeed, using a large number of genetic markers, adaptive population divergence can be demonstrated through the identification of outlier loci (i.e. loci subjected to directional selection; [START_REF] Storz | INVITED REVIEW: Using genome scans of DNA polymorphism to infer adaptive population divergence[END_REF][START_REF] Nielsen | Genomic signatures of local directional selection in a high gene flow marine organism; the Atlantic cod (Gadus morhua)[END_REF]). This approach was already used in fish to detect local adaptation (e.g. [START_REF] Meier | An assessment of the spatial scale of local adaptation in brown trout (Salmo trutta L.): Footprints of selection at microsatellite DNA loci[END_REF][START_REF] Lowry | Breaking RAD: an evaluation of the utility of restriction site-associated DNA sequencing for genome scans of adaptation[END_REF] and could help to pinpoint which populations could have undergone local adaptation.

However, this approach requires that a high-density genetic map is available, which is not the case for many fish species (but see Qiu et al. ( 2018) and references within). Moreover, the loci relevance to demonstrate adaptive phenotypic change remains often uncertain [START_REF] Storz | INVITED REVIEW: Using genome scans of DNA polymorphism to infer adaptive population divergence[END_REF][START_REF] Merilä | Climate change, adaptation, and phenotypic plasticity: the problem and the evidence[END_REF]. These alternative approaches could help to identify biological units of interest, but they are costly and therefore, they are not suitable to develop a pragmatic method (Figure 11). In addition, even though neutral markers are less accurate to highlight differentiations triggered by ecological gradients, they can also reflect differentiations triggered by random processes, which is not the case with adaptive markers.

Take home message

The use of neutral genetic differentiation to highlight population groups with potential divergences in key traits presents some limits. However, alternative strategies also present some limits and/or are difficult to apply. Therefore, overall, the use of neutral markers for the phylogeographic classification appears as a good compromise between the ability to highlight phenotypic divergences and the pragmatism of the approach.

The second strategy promoted the use of a multi-proxy strategy which would allow improving the single-proxy approach used in this work. However, a multi-proxy classification might be hard to achieve because of limitations of each proxy in the frame of a classification (which can also prevent their use in the single-proxy approach). Indeed, establishing a multi-proxy classification would imply (i) the occurrence of 'breaks' in the genetic differentiation which are required to highlight a genetic structure (e.g. genetic differentiation by distance would prevent the establishment of a classification), (ii) to determine arbitrary values to create a classification based on hydrologic distance or the use of arbitrary notions such as hydrographic basins (without considering connections via artificial canals), and (iii) to have significant divergences in ecosystems to be able to perform a habitat classification. Moreover, it is difficult to make a consensus between alternate classifications. It could be performed through clustering analyses and a consensus between the different proxy-based clusters, but this strategy remains sub-optimal. Overall, establishing a classification in step 1 might therefore not be the most optimal approach.

An alternative to the classification approach?

As an alternative, working with distances rather than differentiations would allow overcoming difficulties of establishing a classification. This alternate strategy is based on the ranking and prioritization of populations (the biological unit is the population rather than the prospective unit). It consists of simultaneously testing populations across the distribution range for genetic, habitat, and hydrological distances (i.e. the consideration of these three proxies allows to cover correlations with all key traits distance matrices). With this approach, population pairs which are the most distant (for the three proxies) would be considered for further steps (Figure 12). Although considering populations genetically, hydrologically, and environmentally distant may seem obvious, this step is essential to avoid the random sampling of populations. The number of population pairs considered for the bioassays mainly depends on the capacities of the fish farm/research structure where the step 2 is performed. If the upper capacity is to study two populations, then the two populations which are the most distant across all proxies should be considered (in figure 12 that could correspond to BAL and GEN).

Step 2: Comparing performances in a common-garden environment

2.1 Limits of the step 2

The second step of the integrative approach is probably the most work-intensive step since rearing several populations and evaluating their performance over the full life cycle is challenging and time-consuming. The use of a multi-function and multi-trait approach

Take home message

Overall, establishing an intraspecific classification, either single-or multi-proxy, remains limited since it implies potential arbitrary choices to delineate groups. The single proxy classification worked rather well in this work, but an alternative strategy is proposed here:

prioritizing population pairs using several proxies, rather than classifying. This allows to overcome limits tied to the classification and could simplify the first step of the approach.

increases the workload of this step. However, as shown in the fourth chapter, the single-strait approach is limited and might lead to erroneous conclusions. The multi-trait evaluation is necessary to estimate the potential for aquaculture correctly. This underlines the importance of the first step to limit the number of populations which need to be compared during bioassays.

The common-garden set up allows to state that differences observed between populations are genetically based. However, egg ribbons were spawned in the wild and therefore experienced the environment effect before being transferred to the experimental structures. Differences seen between populations can thus be attributed to (i) phenotypic plasticity, including parental effects mentioned earlier and epigenetic effects and (ii) genetically based differences. The effect of phenotypic plasticity could have been limited through the sampling of broodstock to produce offspring in controlled conditions. However, for Perca fluviatilis, as well as for many other species, first life stages are the preferred wild biological material for fish farmers since mortality rates following transport and acclimatization are high for adults. Moreover, transgenerational effects can still impact the descendants from wild-caught breeders [START_REF] Youngson | Transgenerational epigenetic effects[END_REF][START_REF] Bhandari | Transgenerational effects from early developmental exposures to bisphenol A or 17α-ethinylestradiol in medaka, Oryzias latipes[END_REF]. Therefore, phenotypic plasticity impacts cannot be ruled out when applying the three-step approach, but these latter are limited thanks to the use of a common-garden experiment, even though adaptive epigenetic changes (i.e. heritable; e.g. linked to DNA methylation or histone modifications) could also be of interest, similarly to genetically-based divergences, since they have the potential to influence fitness [START_REF] Klironomos | How epigenetic mutations can affect genetic evolution: Model and mechanism[END_REF].

A (partial) genetic basis (i.e. heritability = fraction of the phenotype variation which can be explained by variation in genotype) was already assessed in other species for several key traits ). Therefore, we can expect that at least a part of these differentiations would be transmitted to following generations, but this still requires further studies. One way to verify that the observed inter-populational differentiations are genetically based would be to continue the experiment for the full life cycle and to verify on the F1 (first generation born in captive conditions) that the same differentiations are observed.

However, the impact of domestication can occur even after only one generation in the culture environment (see further; [START_REF] Christie | A single generation of domestication heritably alters the expression of hundreds of genes[END_REF]. Another solution would be to repeat the performance assessment of wild populations the following year to evaluate the genetic basis of phenotypic differentiation.

One could state that a particular population/PU may perform better than others in the experimental system because it is better adapted to these conditions (e.g. rearing conditions closer to their wild habitat). For instance, as these populations come from different geographic locations, it is likely that their optimal rearing temperatures differ due to local adaptation, although the thermo-tolerance of European perch is quite high. However, this is a concept proof study aiming at highlighting differentiations in key traits for a particular rearing system.

Varying both factors (biological unit [population or PU] and different rearing systems) would be interesting to assess the interaction between genetic and environment variances but it was not the purpose of this work.

2.2 Implications regarding the inter-specific candidate evaluation?

In the introduction of this work, some methods used at the interspecific level to highlight candidate species of interest based on socio-economic and biological criteria were presented (Tables 3 and4). Geographic differentiation was highlighted for several key traits and this calls these methods into question. Indeed, the question can be raised regarding the differentiation between species vs the differentiation within species. A good candidate species could be missed if the evaluation at the inter-specific level is only performed on one population (wild or in controlled conditions) to assess the potential of this particular species.

In the figure 13, I suggest two scenarios. The first scenario would lead to the identification of species 2 as the best candidate species for domestication. Species 1 would not be considered for further domestication trials. In scenario 2, the same conclusion would be drawn. Yet, if geographic differentiation had been taken into account, species 1 would not have been excluded from further evaluation since some populations present a high expression of this key trait. Therefore, the best method would be to evaluate from the beginning geographic differentiation of all species of interest for aquaculture (i.e. species meeting an unsatisfied human demand, need, or interest and has a high socio-economic value). However, this might not be feasible/pragmatic for all new candidate species since it requires time and money.

Therefore, caution should be paid regarding biological characteristics when ranking candidate species for interest for domestication and production (e.g. by putting more weight to socioeconomic criteria than biological criteria). It should be known that a good candidate species could be missed and exclusion of candidate species from the evaluation process should not be based solely on biological characteristics, even though the interspecific differentiation can be expected to be overall higher than the intraspecific differentiation. expressions which are not considered in the evaluation process. The two scenarios would lead to consider species 2 as more suitable for domestication/production than species 1.

Step 3: Identifying units with the highest aquaculture potential

This step requires attributing a weighting coefficient to each trait. Indeed, not all traits are equally important to stakeholders as confirmed by the survey led in the fourth chapter. In our survey, only fish farmers were questioned (12 farms). It would be interesting to include in the survey all stakeholders involved in the industry (e.g. scientists, environmental managers, and socio-economic actors), even though this complicates the weight assessment (i.e. consensus between stakeholders). This weighting step is species dependent, or even species group dependent since some convergences exist. That implicates that a survey will be needed for each new species/species group. Not all traits being equally heritable, one could state that more weight should be put for traits with higher heritability. However, this seems difficult since this approach targets new candidates for domestication (i.e. heritabilities unknown) and traits' heritabilities can be highly variable between species [START_REF] Gjedrem | Basic statistical parameters[END_REF][START_REF] Blonk | Genetic improvement of percids[END_REF].

formula B presents the advantage of better taking into account the deltas of differences between biological units (Table 16).

C. Applicability of the method

Repeatability

As mentioned earlier in this discussion, results obtained could be (partly?) due to nonadaptive epigenetic and/or transgenerational effects which could impede the repeatability of results. The repeatability of results needs to be assessed through the repetition of the experiment and the evaluation of the inter-year variability of performances. In addition, studying additional populations for the Eastern and Danube groups would allow re-enforcing the verification that the differentiation within-PU is lower than the differentiation between-PU.

The results obtained are only valid for the rearing system used. Indeed, we did not assess in this study if there was a genotype x environment interaction (Falconer and Mackay 1996; Sae- [START_REF] Lim | A review of genotype-by-environment interaction and micro-environmental sensitivity in aquaculture species[END_REF]. The presence of such interaction implies that the best biological unit for our rearing system may not be as interesting in different rearing conditions (i.e. genotype presenting different phenotypes in different rearing environments). Therefore, it could prevent the election of a specific PU/population as the best universal biological unit. Yet, given the diversity of aquaculture systems and the will to develop production in diverse systems, it is a factor which would need to be evaluated. The genotype x environment interaction is a factor regularly evaluated in selective breeding programs and has already been studied for several traits and species (e.g. [START_REF] Gunnes | Selection experiments with salmon IV Growth of Atlantic Salmon during two years in the sea[END_REF][START_REF] Ayles | Genetic differences in growth and survival between strains and hybrids of rainbow trout (Salmo gairdneri) stocked in aquaculture lakes in the Canadian prairies[END_REF][START_REF] Saillant | Estimates of heritability and genotypeenvironment interactions for body weight in sea bass (Dicentrarchus labrax L.) raised under communal rearing conditions[END_REF][START_REF] Domingos | Heritability of harvest growth traits and genotype-environment interactions in barramundi, Lates calcarifer (Bloch)[END_REF][START_REF] Turra | Genotype × environment interaction for growth traits of Nile tilapia in biofloc technology, recirculating water and Cage systems[END_REF][START_REF] Srimai | Genetic parameters and genotypeenvironment interaction for growth traits of North African catfish, Clarias gariepinus (Burchell, 1822)[END_REF][START_REF] Li | Genetic parameters and genotype by environment interactions for growth traits and survival of olive flounder (Paralichthys olivaceus) in recirculating aquaculture system and flow-through system[END_REF]. However, in this

Take home message

The three-step method presents some limits, but some are inevitable, and some improvement could overcome the others. However, there is no other standardized method available to date to integrate geographic differentiation in domestication processes.

Therefore, given the interest of considering geographic differentiation and despite its limits, this approach could be greatly useful to facilitate domestication of new species.

Ultimately, this evaluation needs to be performed in a commercial farm to test the method and compare with strategies currently led when starting a new species domestication (i.e.

often sampling random or geographically close wild populations). This would allow validating conclusions drawn and ensure technological transfer. approach, it is not realistic to include this assessment since it requires larger investments and much higher operating costs. It could be checked later when there is a will to develop production in a new rearing environment.

Feasibility

2.1 First and second steps of the integrative method

In the first step, proxies can be evaluated relatively easily (providing the availability of relevant data for the habitat differentiation proxy). However, the genetic assessment could be more challenging. The genetic evaluation requires expertise and equipment for DNA extraction, amplification, and sequencing, as well as data analyses. However, with the fast development of genetic techniques and the appraisal of new markers, genetic analyses costs are decreasing [START_REF] Schlötterer | The evolution of molecular markers -Just a matter of fashion?[END_REF][START_REF] Martinsohn | DNA-analysis to monitor fisheries and aquaculture: Too costly?[END_REF]). In addition, the genetic assessment effort may be shared by stakeholders and/or outsourced. In any case, the transfer and implementation of such approach in commercial practices will likely need a collaborative effort between the industry and scientists.

The second step is a trial and error approach which will be invariably resource-consuming.

This step would need to be performed in any case when starting domestication of a new species population, but testing several biological units requires higher investments. However, the first step restricts possibilities regarding the number of biological units to compare. Even though rearing several biological units across a life cycle is challenging, this step is essential since it is not possible to extrapolate from phenotypic differentiation observed in the wild.

When working on a new species, one difficulty might also be found in the choice of the domestication system. Rearing conditions can be chosen from the knowledge of wild conditions and first trials could be performed to set the domestication environment. It is also possible to get some insights from ecologically related species in order to start rearing trials [START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF]. In addition, one fact that could limit the feasibility of step 2 is the ability to measure accurately some phenotypic traits. Indeed, some traits can be hard to measure accurately (e.g. feed efficiency; [START_REF] Verdal | Quantifying the genetic parameters of feed efficiency in juvenile Nile tilapia Oreochromis niloticus[END_REF] but this is relative to the set of traits chosen before performing bioassays. Finally, as demonstrated in the fourth chapter, some correlations exist between traits. These correlations could help to decrease the number of traits studied and simplify the evaluation of performances. Some correlations are obvious (such as between length and weight which was shown for other species, e.g. [START_REF] Nousias | Parentage assignment, estimates of heritability and genetic correlation for growth-related traits in meagre Argyrosomus regius[END_REF]) but others make little biological sense (e.g. correlation between length at hatching and activity). Overall, this could allow simplifying the set of traits for both phases, but this is specific to our dataset since correlations between traits can vary between species (e.g.

Gjedrem and Olesen 2005).

Additional filters before bioassays?

The ability to survive in culture conditions is a prerequisite for domestication that might or might not be shared by different biological units. Therefore, an improvement of the method could rely on the a priori selection (i.e. before bioassays) of biological units that have this ability. This filtering step could allow limiting the trial and error approach through the evaluation of the suitability of aquaculture conditions for biological units through predictive models (using species distribution models based on occurrence and environmental data).

Beside intrinsic factors which are evaluated in bioassays (e.g. ability to live in high densities), this suitability depends on the similarity between the wild and the culture ecological niches.

This similarity is likely when the culture environment is within the species natural environment (e.g. outdoor aquaculture), but artificial environments (e.g. RAS) can be quite different from the wild, making suitability of culture environment unsettled. The suitability of each biological unit could be evaluated through ecological niche modeling approaches [START_REF] Maxted | Establishment of a global network for the in situ conservation of crop wild relatives: status and needs. Commission on genetic resources for food and agriculture[END_REF][START_REF] Lecocq | Integrating intraspecific differentiation in species distribution models: consequences on projections of current and future climatically suitable areas of species[END_REF]). This approach requires delimitating which environmental factors shape ecological niches. This task is challenging since assessing shaping factors is not easy (see the fifth chapter) and these shaping factors can be different between wild and artificial niches. Therefore, only relevant parameters in the artificial indoor environment need to be considered (e.g. temperature, pH, alkalinity, water velocity). Yet, as mentioned in the fifth chapter, this data is not always available for wild populations. Providing data is available, the suitability between the wild and artificial niches of each biological unit could be assessed using the Hutchinson's hypervolume [START_REF] Hutchinson | Concluding remarks[END_REF]. The overlap between niches

Take home message

Overall, in order to apply this three-step approach, stakeholders need to (i) be convinced of the potential advantages to start new domestication processes considering geographic differentiation, (ii) obtain technical expertise, and (iii) commit resources at the beginning of the domestication process. This last point might be the most plausible impediment as investing in the domestication/production of a new species is financially risky.

could be quantified (with the bias of using realized niche and not fundamental niche).

However, this approach does not allow to take into account tolerance abilities of the different biological units. With our species of concern, it could be expected that all RAS systems could be suitable to all populations since Percids are quite tolerant to abiotic variations (Kestemont et al. 2015a), but this strategy could for instance be useful for species with stenotopic [i.e.

tolerate to a small range of environmental conditions] populations.

In the aquaculture potential score index, there is a minimum threshold expression factor.

Minimum expression thresholds correspond to characteristics which prevent domestication/production, and which are not surmountable at the time of the evaluation.

These species-dependent characteristics could include prerequisites which can be used as filters before bioassays. For example, for Perca fluviatilis, the absence of Perhabdovirus, -a viral pathogen of importance in percid culture- [START_REF] Bigarré | Molecular investigations of outbreaks of Perch perhabdovirus infections in pike-perch[END_REF][START_REF] Rupp | Identification of important pathogens in European perch (Perca fluviatilis) culture in recirculating aquaculture systems[END_REF]) can be considered as a prerequisite. The definition of these prerequisites constitutes an additional filter before bioassays.

Guidelines

Starting domestication with a stock originating from one wild population requires sampling a sufficient number of individuals to (i) avoid future inbreeding issues, (ii) have a representative sampling of the natural population, and (iii) have a sufficient genetic variability for potential future selective breeding programs [START_REF] Vandeputte | Quelle gestion génétique de la domestication chez les poissons?[END_REF][START_REF] Blonk | Genetic improvement of percids[END_REF].

Spreading the sampling across the sampling season and/or across several years can be a solution to avoid sampling a minimal fraction of the total variability [START_REF] Chevassus | Aspects génétiques de la constitution de populations d'élevage destinées au repeuplement[END_REF]).

Genetic variability was not considered here as a prerequisite. Indeed, a lower genetic diversity increases chances to sample kin individuals, increasing risks to have deleterious allele expression and inbreeding issues. However, it is also possible to sample closely related individuals when considering a population with a higher genetic variability. Therefore, it is all a matter of good practice in stock constitution to have a sufficient effective size [START_REF] Lorenzen | Cultured fish: integrative biology and management of domestication and interactions with wild fish[END_REF]. Moreover, temporary disturbances (e.g. disease, unusual food shortage, pollution) can affect performances of sampled individuals. Therefore, the occurrence of unusual events should be verified before the sampling step.

The restrictions regarding sampling and transporting biological material should also be considered when choosing biological units which need to be evaluated in the second step.

Indeed, when sampling biological material is limited or difficult in administrative terms, then populations concerned should be excluded from the assessment. In addition, attention should be paid to the Nagoya Protocol on "access to genetic resources and the fair and equitable sharing of benefits arising from their utilization to the convention on biological diversity".

This international agreement implies that if the genetic resources of a specific country is exploited then benefits should be shared with this country (monetary or not [e.g. royalties]

and sharing of research results). Regarding national rules, even if sampling restrictions are limited to national populations, this approach is still useful in countries with environmental gradients since differential potentials for aquaculture are likely. Finally, since wild ecosystems already support fishing pressure, aquaculture should not increase this pressure.

Therefore, the sourcing of individuals for farmed stock should ideally be performed in a sustainable manner. Moreover, wild stocks from declining/endangered populations should not be used when extensive sampling is planned to provide several farms (except for recovery purposes; [START_REF] Simard | The sustainable development of Mediterranean aquaculture: Problems and perspectives[END_REF]). Yet, producing a particular population could allow decreasing fishing pressure in this site. Therefore, populations which are decreasing because of fishing pressure should not be automatically excluded from the assessment. Overall, the choice of targeted populations depends on several factors such as sampling effort, future uses of wild resources, regulations, and wild population effective site.

Finally, this approach gives an overview of the potential contained in the wild biodiversity at a given time. Therefore, the evaluation is context-dependent and might need to be performed again if the context evolves (e.g. different fish farmers expectations, consumer preference changes [e.g. product quality, age at sexual maturation (Gjedrem 2010)], environmental changes; Figure 15).

A trade-off between advantages and risks

On the one hand, attention should also be paid to the environmental risks of using non-local populations. Indeed, there are risks of escapees of individuals, particularly in outdoor aquaculture but risks cannot be ruled out in indoor aquaculture (Summerfelt and Vinci 2009).

These escapees can trigger negative consequences on the genetic integrity and fitness of locally adapted populations, for instance through genetic homogenization/introgression, competition for resources, or pathogen introduction [START_REF] Ryman | Protection of intraspecific biodiversity of exploited fishes[END_REF][START_REF] Laikre | Genetic population structure of fishes: Implications for coastal zone management[END_REF][START_REF] Weir | Effects of aquaculture on wild fish populations: A synthesis of data[END_REF][START_REF] Marra | When will we tame the oceans?[END_REF][START_REF] Svåsand | GENIMPACT -Evaluation of genetic impact of aquaculture activities on native populations[END_REF][START_REF] Danancher | Genetic population structure in flatfishes and potential impact of aquaculture and stock enhancement on wild populations in Europe[END_REF][START_REF] Arechavala-Lopez | Reared fish, farmed escapees and wild fish stocks -a triangle of pathogen transmission of concern to Mediterranean aquaculture management[END_REF], 2018). The fitness of escaped individuals is often lower than wild conspecifics (but see [START_REF] Dannewitz | Reproductive success of hatchery-produced and wildborn brown trout in an experimental stream[END_REF], implying that few escaped individuals will breed successfully, but risks are not null when the number of escapees is high [START_REF] Muir | Managing to harvest? Perspectives on the potential of aquaculture[END_REF]. The negative impacts on wild populations are particularly well known in Salmonids [START_REF] Hansen | Effects of releasing hatchery-reared brown trout to wild trout populations[END_REF][START_REF] Fleming | Lifetime success and interactions of farm salmon invading a native population[END_REF][START_REF] Mazur | Effect of handling and stocking density on hematocrit, plasma cortisol, and survival in wild and hatchery-reared chinook salmon (Oncorhynchus tshawytscha)[END_REF]Naylor et al. 2005;[START_REF] Bekkevold | Genetic impact of gadoid culture on wild fish populations: predictions, lessons from salmonids, and possibilities for minimizing adverse effects[END_REF][START_REF] Hutchings | The nature of fisheries-and farming-induced evolution[END_REF][START_REF] Bolstad | Gene flow from domesticated escapes alters the life history of wild Atlantic salmon[END_REF][START_REF] Wringe | Extensive hybridization following a large escape of domesticated Atlantic salmon in the Northwest Atlantic[END_REF].

These risks could lead to the promotion of the use of local population for domestication.

Indeed, even if modifications are induced by the domestication environment (see further), it is mostly going to consist of modifications in allele frequencies and selection of variants already existing in the wild. In the same way, risks regarding pathogen load and invasive risk will be lesser compared to exogenous populations.

On the other hand, benefits of using exogenous populations should also be considered in the equation. Indeed, local populations might not be optimal for domestication. Taking as an example our results on Perca fluviatilis larviculture, local French fish farms used originally individuals originating from alpine lakes, including Lake Geneva [START_REF] Khadher | Genetic characterization and relatedness of wild and farmed Eurasian perch (Perca fluviatilis): Possible implications for aquaculture practices[END_REF]).

Yet, we showed that for the larval period, this population presents the lowest aquaculture potential score. On the contrary, the Lake Balaton presents the highest aquaculture potential score and is genetically very distant from populations belonging to the European Plain group.

Overall, production efficiency is one of the major bottlenecks limiting the expansion of the sector. Improving zootechnical performances appears as an efficient solution to reduce production costs (Policar et al. 2019).

The decision on which population should be used for aquaculture is therefore a matter of compromise between risks (for the wild biodiversity) and benefits (degree of performance differentiation; Figure 16). This trade-off is going to be culture system dependent. Indeed, risks are much higher in outdoor aquaculture and less important in indoor aquaculture. For outdoor aquaculture, the use of local populations, adapted to their specific region, makes more sense than importing new populations from distant geographical regions which might not be suitable for local conditions. The decision is also dependent on the domestication goal.

Indeed, if the purpose is restocking, risks are much higher than production for market purposes. The decision resulting from this trade-off must be based on a consensus between the different stakeholders. In the case of rearing exogenous populations, several measures should be followed [START_REF] Simard | The sustainable development of Mediterranean aquaculture: Problems and perspectives[END_REF]): (i) rearing systems must be designed to minimize the escape risk and (ii) research on potential impact of escaped fish should be performed.

Usefulness

In order to improve domestication and subsequent production of new candidate species, most of the efforts are currently put into improving the rearing system through the evaluation of variable abiotic conditions and technological improvements (see for Percids references in Policar et al. 2019). However, a complementary approach consists of focusing on the most interesting biological unit.

Which species/populations?

The three-step integrative approach could be useful in several instances:

(i) New candidate species for diversification of the production: This is the main target of the three-step method. When new candidate species of interest are identified at the inter-specific level (e.g. high market potential), the consideration of geographic differentiation can be helpful to facilitate domestication and subsequent production. The geographic differentiation trials could be performed (i) after first rearing trials with one population (with the risk of using an unsuitable population for the trial) or (ii) from the beginning of the domestication process, using knowledge on ecologically close species [START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF] or wild environment to choose rearing conditions. If first trials are performed with a random population and are successful, the three-step approach is not very advantageous. On the opposite, if first rearing trials with a random population are unsuccessful, then the consideration of geographic differentiation could be useful to increase chances of success rather than abandoning the domestication trial. The time to develop new species production could be reduced which is important since time and cost to develop new species is one of the diversification limitations [START_REF] Muir | Managing to harvest? Perspectives on the potential of aquaculture[END_REF]. Performing first trials with one population seems likely since testing from the beginning different biological units might be too resource-consuming.

However, ideally, geographic differentiation should be considered from the beginning of the domestication process to optimize chances of success.

(ii) Species populations already on the domestication pathway but for which domestication/production is limited because of major bottlenecks. The approach appears particularly useful for species populations which remain in the domestication process at stage two (i.e. when a part of the life cycle is completed but several bottlenecks exist in other parts; e.g. Thunnus thynnus [Actinopterygii, Scombriformes, Scombridae], Anguilla Anguilla; Teletchea and Fontaine 2014). It appears also useful for species which production cannot increase due to diverse biological/socio-economic issues. This is the case of Perca fluviatilis which was used as a test case and for which bottlenecks hamper production. Overall, the three-step approach could be useful for species which are at incipient domestication stages (first three levels), or eventually intermediate stages (i.e. level four), and/or for which there is a need to improve domestication/production.

(iii) Species populations already farmed but for which there is a will to develop production in a new domestication system or for which there is a new demand market: even for species populations which are considered as advanced in the domestication process, there might be new market/societal demands which require starting new domestication processes. Indeed, the will for robust (i.e. "able to grow and keep functioning in the presence of environmental variation") and adaptive (i.e. "able to change in response to gradual changes in mean of environmental cues") animals [START_REF] Vandeputte | Amélioration génétique des poissons: Quelles réalisations et quels défis pour demain?[END_REF][START_REF] Sae-Lim | Breeding and Genetics symposium: Climate change and selective breeding in aquaculture[END_REF], fish meal/oil substitution [START_REF] Naylor | Feeding aquaculture in an era of finite resources[END_REF][START_REF] Bostock | Aquaculture: global status and trends[END_REF][START_REF] Osmond | The future of genetic engineering to provide essential dietary nutrients and improve growth performance in aquaculture: Advantages and challenges[END_REF], and welfare and health management [START_REF] Bostock | Aquaculture: global status and trends[END_REF]) might trigger the need to domesticate new populations. Current farmed stocks might not be appropriate for all new societal/market demands. In addition, because of the diversity of rearing system and the potential genotype x environment interaction, the best-performing unit in one rearing system might not be the best in another environment triggering a re-ranking of biological units according to the rearing system considered. In the presence of such interaction which has been demonstrated for several species and key traits (Sae- [START_REF] Lim | A review of genotype-by-environment interaction and micro-environmental sensitivity in aquaculture species[END_REF], the three-step approach could be performed when considering a new domestication system.

(iv) Further production improvement could be achieved by considering wild genetic resources for selective breeding programs. Introduction of adaptive traits (i.e.

genomic introgression) from wild populations allows to obtain phenotypic novelty in produced stocks when this phenotype is absent from the farmed stock [START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF][START_REF] Warschefsky | Back to the wilds: Tapping evolutionary adaptations for resilient crops through systematic hybridization with crop wild relatives[END_REF]. Potential genetic gains from wild relatives through hybridization have been particularly investigated in crops [START_REF] Maxted | Establishment of a global network for the in situ conservation of crop wild relatives: status and needs. Commission on genetic resources for food and agriculture[END_REF][START_REF] Warschefsky | Back to the wilds: Tapping evolutionary adaptations for resilient crops through systematic hybridization with crop wild relatives[END_REF][START_REF] Dempewolf | Past and future use of wild relatives in crop breeding[END_REF][START_REF] Mammadov | Wild relatives of maize, rice, cotton, and soybean: treasure troves for tolerance to biotic and abiotic stresses[END_REF][START_REF] Janzen | The extent of adaptive wild introgression in crops[END_REF]. For instance, the occurrence of beneficial mutations in wild emmer wheat (Triticum dicoccoides) populations [START_REF] Fu | Elevated mutation and selection in wild emmer wheat in response to 28 years of global warming[END_REF] opens the door to crossbreeding with produced crops in order to obtain climate resilient varieties.

(v) Restocking/Enhancement purposes: the use of geographic differentiation appears less useful when considering enhancement (i.e. increase of natural stocks to enable larger catches) and restocking (i.e. restoration of depleted stocks) of wild populations. Indeed, in these cases local populations should be favored to avoid issues raised in the previous section (e.g. genetic homogenization/introgression, competition; [START_REF] Ward | The importance of identifying spatial population structure in restocking and stock enhancement programs[END_REF][START_REF] Laikre | Compromising genetic diversity in the wild: Unmonitored large-scale release of plants and animals[END_REF]. However, in the case of local populations collapsing or closed areas (i.e. no contact with other water bodies), the three-step integrative approach could be used.

This work can be considered as a steppingstone for further research about the integration of geographic differentiation in domestication process and aquaculture development. The approach, here applied to a freshwater fish species, aims to be extended to other species, particularly marine species presenting bottlenecks such as Atlantic halibut (Hippoglossus hippoglossus), wolf-fish (Actinopterygii, Perciformes, Anarhichadidae, Anarhichas lupus), and various bream (e.g. Diplodus puntazzo [Actinopterygii, Perciformes, Sparidae]), which have been a target for diversification research because of their high sale value [START_REF] Muir | Managing to harvest? Perspectives on the potential of aquaculture[END_REF]. A geographic differentiation was already highlighted for instance for Atlantic halibut (e.g. [START_REF] Jonassen | Geographic variation in growth and food conversion efficiency of juvenile Atlantic halibut related to latitude[END_REF][START_REF] Imsland | The interrelation of growth and disease resistance of different populations of juvenile Atlantic halibut (Hippoglossus hippoglossus L.)[END_REF][START_REF] Imsland | Intraspecific differences in physiological efficiency of juvenile Atlantic halibut Hippoglossus hippoglossus L[END_REF]. However, ultimately the approach aims at being extended to other species groups such as mollusks or arthropods (e.g. shrimp farmed stocks were derived from various geographic locations even though no comparison of performances was performed; Benzie 2009; see also geographic differentiation found for

Octopus vulgaris, a candidate species for marine aquaculture diversification which production is hampered because of high larval mortalities, [START_REF] Garrido | Assessment of stress and nutritional biomarkers in cultured Octopus vulgaris paralarvae: Effects of geographical origin and dietary regime[END_REF].

What about selective breeding programs?

Selective breeding programs have been led for various species such as Salmonids, sea bass and sea bream, tilapia, and shrimps [START_REF] Muir | Managing to harvest? Perspectives on the potential of aquaculture[END_REF][START_REF] Gjedrem | The importance of selective breeding in aquaculture to meet future demands for animal protein: A review[END_REF]. Even though the geographic sampling has been previously used in selective breeding programs, the purpose was to sample a sufficient genetic variation to ensure long-term genetic response in breeding programs [START_REF] Hayes | Use of molecular markers to maximise diversity of founder populations for aquaculture breeding programs[END_REF]) rather than exploiting directly geographic differentiation to start a new domestication process or overcome bottlenecks limiting domestication/production at early domestication stages. Selective breeding programs are considered as long-term investments (baseline breeding program profitable after 5 years; [START_REF] Janssen | Cost-benefit analysis of aquaculture breeding programs[END_REF]) but gains obtained over generations of selection can be very high (e.g. +113% in growth rate over five generations in S. salar; [START_REF] Gjedrem | The importance of selective breeding in aquaculture to meet future demands for animal protein: A review[END_REF]. The usefulness of selective breeding programs is undeniable to improve farmed stocks [START_REF] Pincent | Domestication et amélioration génétique des cheptels piscicoles Français dans le cadre du SYSAAF[END_REF][START_REF] Vandeputte | Amélioration génétique des poissons: Quelles réalisations et quels défis pour demain?[END_REF][START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF]). However, farmed stocks are still today based in majority on genetically unimproved stocks (Gjedrem 2005b).

The three-step approach appears as complementary rather than opposite to selective breeding programs. The principle underlying the three-step approach is overall not very different from selective breeding methods, such as mass selection or family-based programs. Indeed, the need and challenge to phenotype individuals is needed in both approaches, even though advanced selective breeding programs allow working at different scales (i.e. family, individual) with potential control of crosses between breeders and pedigree assessment through genotyping [START_REF] Lind | Selective breeding in fish and conservation of genetic resources for aquaculture[END_REF]. Compared to selective breeding programs, the three-step integrative approach works at a different scale (i.e. population level) and presents potentially the risk of narrowing the genetic variability by focusing on a single biological unit.

However, the prevention of inbreeding remains a management caution and rely on good Indeed, there is a high risk of pathogen transmission when introducing wild individuals in farmed stocks [START_REF] Blonk | Genetic improvement of percids[END_REF]. Moreover, farmed populations (i.e. advanced in the domestication process) were shown to often present better performances than wild individuals (e.g. [START_REF] Fleming | Lifetime success and interactions of farm salmon invading a native population[END_REF][START_REF] Glover | A comparison of farmed, wild and hybrid Atlantic salmon (Salmo salar L.) reared under farming conditions[END_REF]Douxfils et al. 2011b;[START_REF] Lorenzen | Cultured fish: integrative biology and management of domestication and interactions with wild fish[END_REF], even though this is not true for all traits and all species (e.g. [START_REF] Mayer | Domestication causes rapid changes in heart and brain morphology in Atlantic cod (Gadus morhua)[END_REF][START_REF] Khendek | How does a domestication process modulate oogenesis and reproduction performance in Eurasian perch?[END_REF][START_REF] Saraiva | Domestication and welfare in farmed fish[END_REF]Pasquet 2019). Therefore, using wild individuals could potentially erase all gains obtained from successive generations in the rearing environment [START_REF] Blonk | Genetic improvement of percids[END_REF]. Finally, selective breeding programs are particularly interesting when the selective breeding programs differentiation within population is higher than the differentiation between populations [START_REF] Withler | Genetic variation in resistance to bacterial kidney disease within and between two strains of coho salmon from British columbia[END_REF][START_REF] Quillet | Variabilité génétique de la réponse aux organismes pathogènes : un outil pour améliorer la santé des mollusques et poissons d'élevage[END_REF] or when the genetic gain prediction for one generation of individual selection is higher or equal to the between-population differentiation (see for instance [START_REF] Vandeputte | Multi-site evaluation of the rearing performances of 5 wild populations of European sea bass (Dicentrarchus labrax)[END_REF] in which one generation of mass selection is sufficient to equal the magnitude of inter-populational difference). Selective breeding programs could potentially be used after the three-step integrative approach, providing that the genetic variability is sufficient for selection [START_REF] Vandeputte | Quelle gestion génétique de la domestication chez les poissons?[END_REF].

Extrapolation to other species?

Consequent investment may not be operated for each new candidate given the risks of failure when starting domestication of a new species or when facing major bottlenecks. One way to decrease investments could rely on the extrapolation of knowledge acquired on a particular species to another. Some approaches were developed at the inter-specific level to establish some functional classifications (i.e. clustering biological units displaying similar life histories) between wild species (e.g. [START_REF] Balon | Reproductive Guilds of Fishes: A Proposal and Definition[END_REF][START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF]). These approaches based on functional traits were chosen rather than phylogeographic classifications since highly divergent taxa sometimes exhibit biological trait convergences due to the adaptive status of traits [START_REF] Winemiller | Patterns of variation in life history among South American fishes in seasonal environments[END_REF]. The aim of these approaches is to extrapolate knowledge among species belonging to the same cluster [START_REF] Teletchea | Comparative analysis of reproductive traits in 65 freshwater fish species: application to the domestication of new fish species[END_REF]). However, the use of such an approach appears unlikely at the intraspecific level. Indeed, performances observed in the second step are species-and eventually system-specific. Results could probably not be extended to other species, but this remains to be verified. Therefore, until specific experiments are performed to answer this question, the performance evaluation in the second step appears inevitable for all new candidate species.

The first step could eventually be skipped. Indeed, biogeographic convergences could allow extending conclusions of the first step using already available phylogeographic studies.

Indeed, there are some general phylogeographic patterns in co-distributed fishes with common specificities across species [START_REF] Bernatchez | Comparative phylogeography of Nearctic and Paleartic fishes[END_REF][START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF][START_REF] Hickerson | Phylogeography's past, present, and future: 10 years after Avise[END_REF][START_REF] Bowen | Comparative phylogeography of the ocean planet[END_REF][START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF]. This means that a particular population/groups of populations could be genetically distinct since other taxa display genetic specificities in this area. However, even though this can be helpful for freshwater fishes with common phylogeographic patterns, it might be more difficult to apply with marine species. Moreover, the existence of common areas with genetic specificities across co-distributed species is not guaranteeing to find specificities for a target species.

Indeed, the genetic structure can vary quite a lot, even between closely-related species (e.g. Overall, the extrapolation of conclusions is unlikely, and the approach should therefore be applied in priority to species with a very high economic interest and facing major bottlenecks.

As mentioned earlier, regarding the extrapolation between rearing systems, this does not appear as possible if there is a significant interaction between genotype and environment.

What is next?

7.1 Domestication: a continuum of modifications

The three-step integrative method aims at identifying biological units of interest at the beginning of the domestication/production process. However, how will performances of these units change along domestication?

The domestication environment is often quite different from the wild environment, particularly in indoor culture. Therefore, this implies that there is a new set of selective pressures that will change gene frequencies. The transfer from the wild to breeding systems happens in concomitance with [START_REF] Price | Behavioral development in animals undergoing domestication[END_REF][START_REF] Vandeputte | Quelle gestion génétique de la domestication chez les poissons?[END_REF][START_REF] Boissy | Genetics of adaptation and domestication in livestock[END_REF][START_REF] Groeneveld | Genetic diversity in farm animals -A review[END_REF][START_REF] Gering | Maladaptation in feral and domesticated animals[END_REF]):

(i) Non-controlled processes such as inbreeding (i.e. mating between closelygenetically individuals which leads to a decrease of fitness and a genetic diversity loss) and random genetic drift (i.e. change in allele frequency(ies) in a population due to chance/sampling error).

(ii) Semi-controlled processes which are the relaxation of natural selection (i.e.

reduction of the selective pressure on traits which are essential in the wild but not in captivity) and natural selection in captivity (i.e. selection of individuals with higher fitness in captivity).

(iii) Controlled processes which correspond to artificial selection programs (i.e. process in which breeders consciously select for or against particular traits).

Therefore, the domestication process leads to some phenotypic and genetic changes [START_REF] Price | Behavioral development in animals undergoing domestication[END_REF][START_REF] Balon | About the oldest domesticates among fishes[END_REF][START_REF] Driscoll | a) From wild animals to domestic pets, an evolutionary view of domestication[END_REF], including potential epigenetic modifications [START_REF] Feeney | Epigenetics and transgenerational inheritance in domesticated farm animals[END_REF]. Domestication consequences are sometimes visible as early as in the first generation [START_REF] Vandeputte | Génétique et adaptation chez les poissons: Domestication, résistance au stress et adaptation aux conditions de milieu[END_REF][START_REF] Dunham | Aquaculture and Fisheries Biotechnology, Genetic Approaches, 2nd Edition[END_REF][START_REF] Christie | A single generation of domestication heritably alters the expression of hundreds of genes[END_REF][START_REF] Roussel | Anti-predator response of Haliotis tuberculata is modified after only one generation of domestication[END_REF]. Morphological, physiological, and behavioral changes through the domestication process refer to the "domestication syndrome" [START_REF] Olsen | A Bountiful harvest: genomic insights into crop domestication phenotypes[END_REF][START_REF] Larson | The evolution of animal domestication[END_REF][START_REF] Wilkins | The "domestication syndrome" in mammals: A unified explanation based on neural crest cell behavior and genetics[END_REF]. For instance, phenotypic changes attributed to domestication have been highlighted for growth [START_REF] Clutton-Brock | A natural history of domesticated mammals[END_REF][START_REF] Tymchuk | Growth differences among first and second generation hybrids of domesticated and wild rainbow trout (Oncorhynchus mykiss)[END_REF][START_REF] Glover | A comparison of farmed, wild and hybrid Atlantic salmon (Salmo salar L.) reared under farming conditions[END_REF]), reproductive traits [START_REF] Schütz | QTL analysis of a red junglefowl × White Leghorn intercross reveals trade-off in resource allocation between behavior and production traits[END_REF][START_REF] Osure | Evaluation of reproductive performance and early growth of four strains of Nile tilapia (Oreochromis niloticus, L) with different histories of domestication[END_REF][START_REF] Krejszeff | Domestication affects spawning of the ide (Leuciscus idus)-preliminary study[END_REF][START_REF] Khendek | How does a domestication process modulate oogenesis and reproduction performance in Eurasian perch?[END_REF][START_REF] De Almeida | Domestication may affect the maternal mRNA profile in unfertilized eggs, potentially impacting the embryonic development of Eurasian perch (Perca fluviatilis)[END_REF], immune parameters [START_REF] Douxfils | Influence of domestication process on immune response to repeated emersion stressors in Eurasian perch (Perca fluviatilis, L.)[END_REF][START_REF] Christie | A single generation of domestication heritably alters the expression of hundreds of genes[END_REF], stress response [START_REF] Mazur | Effect of handling and stocking density on hematocrit, plasma cortisol, and survival in wild and hatchery-reared chinook salmon (Oncorhynchus tshawytscha)[END_REF]Douxfils et al. 2011a), or behavior [START_REF] Ruzzante | Domestication effects on aggressive and schooling behavior in fish[END_REF][START_REF] Price | Animal Domestication and Behavior[END_REF][START_REF] Huntingford | Implications of domestication and rearing conditions for the behavior of cultivated fishes[END_REF]Pasquet 2019). Features of the domestication syndrome are not universal, but some common features can be seen across taxa.

Research aiming at determining the origin of this domestication syndrome remains ongoing.

However, in vertebrates, one major hypothesis raised in the literature relies on neural crest cells [START_REF] Wilkins | The "domestication syndrome" in mammals: A unified explanation based on neural crest cell behavior and genetics[END_REF][START_REF] Sánchez-Villagra | The taming of the neural crest: A developmental perspective on the origins of morphological covariation in domesticated mammals[END_REF]). These cells appear during embryogenesis at the dorsal edge of the neural tube. Along development, they migrate ventrally throughout the body and are the precursors of several tissues and cell types (e.g. adrenal medulla, external ears, odontoblasts). The initial selection for tameness at the beginning of the domestication process could lead to a reduction of the number of neural crest cells at final sites, which triggers unselected morphological changes [START_REF] Wilkins | The "domestication syndrome" in mammals: A unified explanation based on neural crest cell behavior and genetics[END_REF][START_REF] Sánchez-Villagra | The taming of the neural crest: A developmental perspective on the origins of morphological covariation in domesticated mammals[END_REF]). However, neural crest cell might only be part of the explanation and studies still need to be performed to validate this hypothesis across taxa.

These numerous changes imply that differentiation in performances between allopatric populations/PUs might not be preserved through generations. However, this approach aims at starting with the best biological unit available in the wild. Therefore, even though modifications occur through domestication, the use of a particular population will allow to start domestication/production with higher chances of success and/or to overcome major bottlenecks in domestication/production.

What to do with units with high potential for aquaculture?

If several biological units of interest are identified or if all biological units are at the same level of interest (i.e. same aquaculture potential), we can wonder what the strategy to adopt is.

On the one hand, the focus could be set on a particular unit or some units could be reared separately (similarly to purebreeding in selective breeding programs). This would allow keeping the specificities of populations. However, this strategy was said to be more efficient when one biological unit presents significantly better performances than others (Gjedrem 2005b). On the other hand, crosses could be made between biological units, which are particularly interesting if there is heterosis (i.e. hybrid vigor). Heterosis has already been highlighted for several species such as Nile tilapia or rainbow trout [START_REF] Ayles | Genetic differences in growth and survival between strains and hybrids of rainbow trout (Salmo gairdneri) stocked in aquaculture lakes in the Canadian prairies[END_REF][START_REF] Gjedrem | Genetic improvement for the development of efficient global aquaculture: A personal opinion review[END_REF]. However, crossing genetically differentiated stocks for aquaculture production is delicate since the optimum for heterosis (i.e. hybrid vigor) is just beyond the one where fitness decreases. Indeed, interbreeding between populations which are genetically distinct can lead to outbreeding depression and a reduction of fitness (except in the case of heterosis). Yet, this strategy could be wished if there is a will to create a common founder stock for production and that fish farmers expectations are divergent ("consensus" unit creation).

Assessing the geographic differentiation causes?

Identifying shaping factors structuring genetic and phenotypic differentiations has been a

wide topic of research in evolutionary biology. Natural selection exerts a pressure towards genotypes which favor fitness in a given environment [START_REF] Ward | The importance of identifying spatial population structure in restocking and stock enhancement programs[END_REF]. Adaptive differentiation can result from barriers to gene flow and/or environmental differences (Heibo et al. 2005;[START_REF] Rundle | Ecological speciation[END_REF][START_REF] Hauser | Paradigm shifts in marine fisheries genetics: ugly hypotheses slain by beautiful facts[END_REF] [START_REF] Hauser | Paradigm shifts in marine fisheries genetics: ugly hypotheses slain by beautiful facts[END_REF][START_REF] Zamudio | Phenotypes in phylogeography: Species' traits, environmental variation, and vertebrate diversification[END_REF]. Local adaptation can be prevented (i.e. non adaptive or maladaptive genetic changes) by high gene flow, high genetic drift in small populations, or if genetic variability is not sufficient (i.e. adaptive potential not sufficient to reach optimal adaptation) [START_REF] Kawecki | Conceptual issues in local adaptation[END_REF][START_REF] Merilä | Climate change, adaptation, and phenotypic plasticity: the problem and the evidence[END_REF][START_REF] Faulks | Genetic and morphological divergence along the littoral-pelagic axis in two common and sympatric fishes: perch, Perca fluviatilis (Percidae) and roach, Rutilus rutilus (Cyprinidae)[END_REF]. The stability of selective pressures influences the strategy of populations.

Indeed, when selective pressures are stable through time, disruptive selection favors specific genotypes. On the opposite, when selective pressures are variable, phenotypic plasticity is favored (alternative phenotypes preserved through generations). Phenotypic changes can therefore be plastic or genetic, and these two processes are not exclusive [START_REF] Faulks | Genetic and morphological divergence along the littoral-pelagic axis in two common and sympatric fishes: perch, Perca fluviatilis (Percidae) and roach, Rutilus rutilus (Cyprinidae)[END_REF]. Indeed, phenotypic plasticity is often seen as a step in the phenotypic evolution which leads to the evolution of a canalized phenotype when selective pressures are not variable. This is referred as genetic assimilation (i.e. trait becomes 'fixed' in a population; West-Eberhard 2003;[START_REF] Pigliucci | Phenotypic plasticity and evolution by genetic assimilation[END_REF][START_REF] Aubret | Genetic assimilation and the postcolonization erosion of phenotypic plasticity in island tiger snakes[END_REF][START_REF] Ehrenreich | Genetic assimilation: a review of its potential proximate causes and evolutionary consequences[END_REF].

Wild breeders have undergone generations of selection in their wild environment.

Therefore, selective pressures are undoubtedly different between biological units. The identification of selective pressure leading to local adaptation is not easy (Merilä and Hendry 2014) but several factors were suggested for a few key traits such as temperature, heterogenous and fluctuating environments, predation pressure, resources availability and diversity, or population density [START_REF] Foster | The geography of behavior: an evolutionary perspective[END_REF][START_REF] Schluter | The ecology of adaptive radiation[END_REF]Heibo et al. 2005;[START_REF] Rundle | Ecological speciation[END_REF][START_REF] Marcil | Genetic and environmental components of phenotypic variation in body shape among populations of Atlantic cod (Gadus morhua L.)[END_REF][START_REF] Olsson | Effects of resource level and habitat type on behavioral and morphological plasticity in Eurasian perch[END_REF][START_REF] Valente | What determines growth potential and juvenile quality of farmed fish species?[END_REF][START_REF] Rosburg | Growth potential and genetic diversity of yellow perch in South Dakota[END_REF][START_REF] Gering | Maladaptation in feral and domesticated animals[END_REF]. Intra-and interspecific competitions are also known factors leading to genetic variation and phenotypic differentiation [START_REF] Faulks | Genetic and morphological divergence along the littoral-pelagic axis in two common and sympatric fishes: perch, Perca fluviatilis (Percidae) and roach, Rutilus rutilus (Cyprinidae)[END_REF]. One way to demonstrate local adaptation is the use of reciprocal transplants in the wild, by transplanting populations between wild habitats [START_REF] Kawecki | Conceptual issues in local adaptation[END_REF][START_REF] Merilä | Climate change, adaptation, and phenotypic plasticity: the problem and the evidence[END_REF]. For instance, a transplant experiment of guppies Poecillia reticulata highlighted adaptation to predation on guppy behavior (schooling) and morphology [START_REF] Magurran | Variation in schooling and aggression amongst guppy (Poecilia Reticulata) populations in Trinidad[END_REF][START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF]. However, even though previously used (e.g. [START_REF] Magurran | The behavioral diversity and evolution of guppy, Poecilia reticulata, populations in Trinidad[END_REF][START_REF] Declerck | Evidence for local adaptation in neighbouring Daphnia populations: A laboratory transplant experiment[END_REF]), these approaches are nowadays often impossible due to legal, pragmatic, and ethical reasons [START_REF] Kawecki | Conceptual issues in local adaptation[END_REF]). An alternative approach could rely on experimental evolution studies. It consists in exposing populations to different selective pressure under controlled conditions [START_REF] Kawecki | Experimental evolution[END_REF][START_REF] Merilä | Climate change, adaptation, and phenotypic plasticity: the problem and the evidence[END_REF]. Laboratory natural selection experiments have been performed by fixing the environmental driver(s) causing selection to quantify genetically-based phenotypic changes [START_REF] Bennett | Rapid evolution in response to high-temperature selection[END_REF][START_REF] Sunday | Evolution in an acidifying ocean[END_REF]; see examples in [START_REF] Kawecki | Experimental evolution[END_REF]). However, these experiments are hardly feasible except for species with very short generation times (e.g. bacteria, drosophila) and a rigorous control of experimental conditions is required. An alternative could consist in establishing correlations between phenotypic differentiation seen in a common-garden experiment (due to genetic differentiation and/or adaptive epigenetic changes) and potential selective pressure in the wild as a first approximation even though this hypothesizes that current selective pressures are the ones determining phenotypic differentiation (and not past selective pressures).  Representing experience: I was a student representative at the Scientific Pole A2F "Agronomy, Agrifood, Forests" between 2016 and 2018. This experience allowed me to obtain a better understanding of how the academic system works, research recruitment, and grant application processes.

RÉSUMÉ SUBSTANTIEL EN FRANCAIS

La demande en protéines aquatiques ne cesse d'augmenter au niveau mondial dû à l'augmentation de la population et de la consommation en produits aquatiques.

Historiquement, la pêche permettait de subvenir à cette demande croissante. Cependant, depuis la fin des années 1980, les captures de la pêche stagnent, voire diminuent. La

Figure 1 :

 1 Figure 1: A. World population and fish apparent consumption. B. World fisheries and aquaculture production between 1950 and 2016. Adapted from FAO (2018).

Figure 2 :

 2 Figure 2: Families and biological functions/other traits studied in articles included in the geographic differentiation review in controlled conditions (N=177).

Figure 3 :

 3 Figure 3: European perch (Perca fluviatilis). Credit: A) Yannick Ledoré, B) Sascha Antipine, C) Roland Roesch.

Figure 4 :

 4 Figure 4: Native distribution range (in green) and introduction zones (in dashed green) of the European perch (Perca fluviatilis). From Stepien and Haponski (2015).

Figure 5 :

 5 Figure 5: European perch egg ribbons. Credit: A) and B) Yannick Ledoré; C) Daniel Zarski; D) Lola Toomey.

Figure 6 :

 6 Figure 6: Major bottlenecks limiting Perca fluviatilis production.

Figure 7 :

 7 Figure 7: Mitochondrial D-loop haplotype distribution of Perca fluviatilis in Europe. The colors of the diagrams correspond to the first clade level identified in Nesbø et al. (1999).

Figure 8 :

 8 Figure 8: Rearing system. A. Experiment set up for each population with three cylindroconical tanks. B. Hatchery table with racks. C. Top of the cylindro-conical tank. D. Drawing detailing the experimental set up and the water flow.

Figure 9 :

 9 Figure 9: Major developmental events of Perca fluviatilis during larval and juveniles stages according to Kupren et al. (2019).

Figure 10 :

 10 Figure 10: Larva from Lake Geneva at 21 days post-hatching.

Figure 11 :

 11 Figure 11: Comparison of different methods which could be used to classify populations according to their accuracy (i.e. in highlighting populations presenting divergences in key traits) and their feasibility (i.e. pragmatism).

Figure 12 :

 12 Figure 12: Figure illustrating the prioritization of populations for phase I. Pairwise comparisons of populations are plotted (blue squares) according to three proxies (genetic, hydrologic, and habitat distances).

Figure 13 :

 13 Figure 13: Hypothetical scenarios regarding the expression of a key trait considered as a facilitating characteristic for domestication/production. Two species are screened, and one population is considered (in blue) for the assessment. In red are represented other conspecific populations' expressions which are not considered in the evaluation process. The two scenarios would lead to consider species 2 as more suitable for domestication/production than species 1.

Figure 14 :

 14 Figure 14: A. Aquaculture potential index formula using the ranking method. B. Aquaculture potential index formula using the standardized values of traits.

Figure 15 :

 15 Figure 15: Conceptual figure showing the dependency of the identification of units with high aquaculture potential to the specific context (stakeholders' expectations and environmental changes).

Figure 16 :

 16 Figure 16: Conceptual figure regarding the trade-off between risks and advantages in the choice of the founding population(s).

Figure 17 :

 17 Figure 17: Comparison of the usefulness of the three-step integrative approach and selective breeding programs.

2

 2 Why can geographic differentiation facilitate domestication?

  et al. 2010). Finally, geographic differentiation is strongly suspected to have contributed to the successful cultivation of several cereals. Evidence of multiple domestications of conspecific allopatric populations, afterwards used to develop several strains at advanced domestication levels, was shown for several species such as Oryza sativa (Angiosperms, Rasmont et al. (2008) Poales, Poaceae; Sweeney and McCouch 2007), Hordeum vulgare (Angiosperms, Poales, Poaceae; Morrell and Clegg 2007; Saisho and Purugganan 2007), and Phaseolus vulgaris (Angiosperms, Fabales, Fabaceae; Chacón S et al. 2005).

  divergence and local adaptation (or random processes), (ii) environmentally-induced phenotypic plasticity (i.e. "ability of a single genotype to exhibit a range of different phenotypes in response to variation in the environment"; Forsman 2015), or (iii) a combination of both factors[START_REF] Dewitt | Phenotypic variation from single genotypes : a primer[END_REF][START_REF] Merilä | Climate change, adaptation, and phenotypic plasticity: the problem and the evidence[END_REF]. This implies that phenotypic differentiation observed in the wild between allopatric populations Box 3: Illustration of species mentioned for geographic differentiation

Figure 1 :

 1 Figure 1: A. World population and fish apparent consumption. B. World fisheries and aquaculture production between 1950 and 2016. Adapted from FAO (2018).

Figure 2 :

 2 Figure 2: Families and biological functions/other traits studied in articles included in the geographic differentiation review in controlled conditions (N=177).

Figure 3 :Figure 4 :

 34 Figure 3: European perch (Perca fluviatilis). Credit: A) Yannick Ledoré, B) Sascha Antipine, C) Roland Roesch

Figure 5 :

 5 Figure 5: European perch egg ribbons. Credit: A) and B) Yannick Ledoré; C) Daniel Zarski; D) Lola Toomey

Figure 6 :

 6 Figure 6: Major bottlenecks limiting Perca fluviatilis production.

Figure 7 :

 7 Figure 7: Mitochondrial D-loop haplotype distribution of Perca fluviatilis in Europe. The colors of the diagrams correspond to the first clade level identified in[START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF]. Numbers correspond to populations studied (the Siberian population is not represented here). The white regions correspond to the areas which were glaciated during the last glaciations. From[START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF].

Figure 8 :+

 8 Figure 8: Rearing system. A. Experiment set up for each population with three cylindro-conical tanks. B. Hatchery table with racks. C. Top of the cylindro-conical tank. D. Drawing detailing the experimental set up and the water flow. Credit: L. Toomey.

Fig. 1 :

 1 Fig. 1: Boxplots representing group structure and aggressive interaction results for experiment I (n=3330). Four measures of group structure are presented: inter-individual distances, variance of interindividual distances, nearest neighbour distances, and activity. The black line represents the median, the outsider box corresponds to lower and upper quartile values and white dots correspond to most extreme values within 1.5 times the interquartile range from the ends of the box. Different letters indicate significant differences between populations (P < 0.05) using post hoc tests.

Fig. 2 :

 2 Fig.2: Boxplots representing group structure and aggressive interaction results for experiment II (n=1080). Four measures of group structure are presented: inter-individual distances, variance of interindividual distances, nearest neighbour distances and activity. Aggressive interactions results include aggressive interaction rate, enucleation rate, cannibalism rate, and mortality rate caused by aggressive interactions. The black line represents the median, the outsider box corresponds to lower and upper quartile values and white dots correspond to most extreme values within 1.5 times the interquartile range from the ends of the box. Different letters indicate significant differences between populations (P < 0.05) using post hoc tests.

CHAPTER 2 :

 2 Unlocking the intraspecific aquaculture potential from the wild biodiversity to facilitate aquaculture development In press in Reviews in Aquaculture in 2020

Figure 1 :

 1 Figure 1: Overview of the three-step integrative approach. The step 1 highlights the different prospective units (PU). A population representative of the prospective unit is sampled between steps 1 and 2. Category 1 includes biological traits measured on a group of individuals of the target prospective unit which reflect the fitness (i.e. ability to survive, grow and reproduce) in captive conditions. Category 2 includes biological traits which are specifically relevant to a particular production system (e.g. RAS, pond, raceway) and/or a specific production goal (e.g. fillet, whole fish sale). Category 3 includes biological traits linked to the interaction between the group of individuals and the rearing system which could impact surrounding environments. Category 4 includes biological traits relative to future major challenges and disturbances. In order to simplify the figure, only one trait is represented for each category in the step 2.

  applied in fish species to classify at the intraspecific level. Nevertheless, phenotypic traits can be unreliable since there can be a part of subjectivity when defining and interpreting character states[START_REF] Miralles | The integrative future of taxonomy[END_REF]) and it often requires extensive investigation of inter-individual variability[START_REF] Haig | Taxonomic Considerations in Listing Subspecies Under the U.S. Endangered Species Act[END_REF]. Moreover, some phenotypic traits can be plastic and might not reflect population-specific histories or local adaptations[START_REF] Vogler | Diagnosing Units of Conservation Management[END_REF][START_REF] Joyce | Do taxonomic divisions reflect genetic differentiation? A comparison of morphological and genetic data in Coenonympha tullia (Müller), Satyrinae[END_REF]). These concerns have led to criticisms regarding the relevance and the efficiency of phenotype-based intraspecific classifications (e.g.[START_REF] Mallet | Subspecies, semispecies, superspecies[END_REF][START_REF] Patten | Null expectations in subspecies diagnosis[END_REF]. Although phenotype information could still be useful under the condition that trait variations are indicative of underlying genetic divergences (e.g. morphology in brown trout [Salmo trutta];[START_REF] Pakkasmaa | Morphological differentiation among local trout (Salmo trutta) populations[END_REF][START_REF] Kalayci | Genetic and molecular evidence that brown trout Salmo trutta belonging to the Danubian lineage are a single biological species[END_REF], such classifications must be applied prudently.

  ; Suquet 2010; Alvarez-Lajonchère and Ibarra-Castro 2013; at the intraspecific level Toomey et al. under review). These scoring methods, or other indexes available in literature (e.g. similarly to the selection index, Gjedrem 2005a), could be used to evaluate the aquaculture potential at the intraspecific level.

Figure S1 :

 S1 Figure S1: Barplots representing the estimation of importance (in %) for all traits included in the survey for Percids (Perca fluviatilis and Sander lucioperca; graphs on the left column) and Sturgeons (Acipenser ruthenus, Acipenser gueldenstaedtii, Acipenser stellatus, Acipenser baerii, Acipenser persicus, Hybrid Bester, and Huso Huso; graphs on the right column). Barplots represent different group of traits: reproduction period, larval

  Getting off on the right foot: integration of spatial distribution of genetic variability for aquaculture development and regulations, the European perch case Published in Aquaculture in 2020doi: 10.1016/j.aquaculture.2020.734981  Specific Goal: Classifying wild populations in groups genetically differentiated in order to restrict the number of populations to study in the step 2. The classification aims at maximizing inter-group differentiation and minimizing intra-group differentiation.

  Finally, the mixing of individuals from different refugia in newly colonized areas created regions of high genetic diversity (i.e. suture zones;[START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF] Hewitt 2004b). Moreover, species intrinsic features (e.g. limited dispersal, (partial) postzygotic reproduction isolation) can also contribute to shape local genetic specificities of populations[START_REF] Behrmann-Godel | Evolutionary mechanisms of population divergence in Eurasian perch[END_REF][START_REF] Lecocq | Conservation genetics of European bees: new insights from the continental scale[END_REF][START_REF] Lecocq | Divergent geographic patterns of genetic diversity among wild bees: Conservation implications[END_REF]. This has resulted in an uneven distribution of the genetic variability (i.e. genetic diversity and genetic differentiation) across species ranges[START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF] Hewitt 2004b).Meeting human nutritional needs has often required the domestication (sensu[START_REF] Lecocq | Insects: the disregarded domestication histories[END_REF] and trade of wild animal species[START_REF] Salo | Diagnosing wild species harvest : resource use and conservation[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Velthuis | A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination[END_REF]. However, this development is characterized by challenges which can impede the sustainability of animal production. Successfully domesticating a novel species is a long-term and difficult task since it implies mastering species life cycle in a humancontrolled environment (see production development pathways in[START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]. Furthermore, translocation of individuals within and outside the species native range can occur when the production and subsequent trade begin. This can lead to many conservation concerns (e.g. biological invasion, pathogen spillover, genetic homogenization;Lecocq et al. 2016a;[START_REF] Mack | Biotic invasions: Causes, epidemiology, global consequences, and control[END_REF][START_REF] Perrings | International cooperation in the solution to traderelated invasive species risks[END_REF]. Knowledge of spatial genetic variability patterns provides key information to enhance animal production development as

  selected four mitochondrial regions, commonly used to evaluate phylogeographic patterns of fish species[START_REF] Costedoat | Quaternary pattern of freshwater fishes in Europe: Comparative phylogeography and conservation perspective[END_REF][START_REF] Makhrov | Dispersal routes and species identification of freshwater animals in Northern Europe: a review of molecular evidence[END_REF]: cytochrome b (Cytb), D-loop or control region (D-loop), 16S rRNA (16S), and cytochrome oxidase I (COI).Polymerase chain reaction amplifications of Cytb, D-loop, 16S, and COI were carried out using primers L14724F / H15918R[START_REF] Song | Phylogenetic relations among percid fishes as inferred from mitochondrial cytochrome b DNA sequence data[END_REF], HV2 / CSBD(Nesbø et al. 1998a), 16Sar / 16Sbr[START_REF] Palumbi | The Simple Fool's Guide to PCR[END_REF], and jgLCO1490 / jgHCO2198[START_REF] Geller | Redesign of PCR primers for mitochondrial cytochrome c oxidase subunit I for marine invertebrates and application in all-taxa biotic surveys[END_REF], respectively. The reaction components were 10 pmol primers, PPP MasterMix (Top Bio®), DNA (100 -200 ng/µL), and water. An initial step of five minutes at 95 °C was followed by 38 cycles of denaturation at 94 °C for 40 s, 50 s at annealing temperature (55.8 °C for 16S, 49 °C for COI, 55 °C for Cytb and D-loop), and one minute extension at 72 °C, and a 10 min final extension at 72 °C. We purified PCR products with E.Z.N.A.® Gel Extraction Kit (Omega Bio-tek®) and single read sequencing was performed by Macrogen Europe (Amsterdam, Netherlands) on a 3730XL (Applied Biosystems) using primers H15918R, CSBD, 16Sbr, and jgLCO1490. We edited sequences of mitochondrial markers using CodonCode Aligner 7.1.2 (CodonCode Corporation, Dedham, Massachusetts, USA). The P.

Figure 1 :

 1 Figure 1: Sampling map for Perca fluviatilis. Sampling sites are represented by black circles and juxtaposed numbers indicate the number of individuals sampled at each site.

Figure 2 :

 2 Figure 2: Mitochondrial haplotype network, distribution of genetic diversity and population structure of Perca fluviatilis. (A) Mitochondrial median-joining haplotype network and spatial distribution of haplotype frequencies based on the concatenated alignment. In the network, each haplotype is represented by a circle, circle sizes are relative to haplotype frequencies and numbers correspond to the number of mutations that differentiates haplotypes (absence of number corresponding to a single mutation). Red squares on lines represent undetected/extinct intermediate haplotype states. Black circles correspond to P. fluviatilis sequences, empty red circles to Perca flavescens sequences, and empty blue circles to Perca schrenkii sequences. The adjacent map reports the haplotype frequencies in each sampling site and corresponding pie chart colors refer to the corresponding haplotype color of the network. Pie chart sizes are relative to the number of individuals

  and the Alpine Foreland (hereafter called Danube), and (v) the Balkans. Mapping of spatial distribution of genetic diversity shows some hotspots across the species range (Fig.2B): (i) in the eastern diagonal which reflects the suture zone between the European Plain and eastern Europe clusters, (ii) in northern Finland where west-northern Fennoscandia and eastern Europe clusters co-occur, and (iii) in the Alpine Foreland, north of the Danube basin, and in Slovenia where European Plain and Danube clusters meet. Microsatellites-based analyses highlight a similar uneven distribution of the genetic variability. Although more genetic diversity hotspots occur in western Europe, the population structure is overall a subdivision of mitochondrial clusters (Fig.2C-D). Microsatellites-based results should be carefully considered since they are based on a limited sampling size but their congruence with mitochondrial DNA-based analyses tends to support their relevance (Fig.2). The differences between the two types of genetic information are most likely due to nuclear genome specificities in effective population size and mutation rates[START_REF] Arif | Molecular markers for biodiversity analysis of wildlife animals : a brief review[END_REF][START_REF] Johnson | Contrasting patterns of mitochondrial and microsatellite population structure in fragmented populations of greater prairie-chickens[END_REF][START_REF] Selkoe | Microsatellites for ecologists: a practical guide to using and evaluating microsatellite markers[END_REF] that increase the variability of microsatellite dataset making short-range differentiation more likely (as observed in other species; e.g.[START_REF] Wirth | Genetic evidence against panmixia in the European eel[END_REF]).

  ):(i) in the west of the European Plain (between 5°E and 20°E), (ii) in the north-east of the European Plain (potentially located in a large ice dammed lake east of the north European ice sheet;[START_REF] Mangerud | Ice-dammed lakes and rerouting of the drainage of northern Eurasia during the Last Glaciation[END_REF][START_REF] Maslenikova | Where was the outlet of the ice-dammed Lake Komi, Northern Russia?[END_REF], and (iii) in the upper part of the Danube drainage basin (i.e. west of 20°E). Two other areas may also have acted as refugia: the Balkans and the west-northern Fennoscandia since they host endemic haplotypes.However, the low genetic variability and the lack of sufficient amount of samples from the above areas makes difficult to assess if these regions (i) were refugia in which repeated or protracted bottleneck events decreased the local genetic diversity[START_REF] Avise | Phylogeography: The History and Formation of Species[END_REF][START_REF] Petit | Glacial refugia: Hotspots but not melting pots of genetic diversity[END_REF] or (ii) were secondarily colonized from one of the three main refugia and then underwent local genetic differentiation[START_REF] Kotlík | Phylogeography of the barbel (Barbus barbus) assessed by mitochondrial DNA variation[END_REF]. Additional sampling from eastern drainages and western Fennoscandia are needed to test these hypotheses.The sub-structuring of mitochondrial DNA-based clusters detected by the microsatellite analyses and previous studies (e.g.[START_REF] Bergek | Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)[END_REF][START_REF] Butkauskas | Investigations into genetic diversity of the perch inhabiting Ignalina nuclear power plant cooler and other inland water bodies of Lithuania on the basis of mtDNA analysis[END_REF][START_REF] Olsson | Genetic population structure of perch Perca fluviatilis along the Swedish coast of the Baltic Sea[END_REF]) is most likely due to local differentiation phenomena fostered by species intrinsic features. First, the species natal homing behavior reduces gene flow between populations leading to local genetic structuring[START_REF] Järv | Migrations of the perch (Perca fluviatilis L.) in the coastal waters of western Estonia[END_REF]. Second, species short migration distances (from one to 20 km;Stepien et al. 2015;[START_REF] -Zamora | Quantifying the activity and movement of perch in a temperate lake by integrating acoustic telemetry and a geographic information system[END_REF] can further increase the structuring at local geographic scale by decreasing gene flow between adjacent populations. Third, selective disadvantage of foreign individuals due to local environmental conditions and (partial) post-zygotic reproduction isolation between allopatric populations observed in P. fluviatilis[START_REF] Behrmann-Godel | Evolutionary mechanisms of population divergence in Eurasian perch[END_REF][START_REF] Behrmann-Godel | Kin and population recognition in sympatric Lake Constance perch (Perca fluviatilis L.): can assortative shoaling drive population divergence?[END_REF], 2004;[START_REF] Behrmann-Godel | First evidence for postzygotic reproductive isolation between two populations of Eurasian perch (Perca fluviatilis L.) within Lake Constance[END_REF] can limit gene flow and shape genetic differentiation between neighboring populations.

Figure S1 :

 S1 Figure S1: Sampling map for Perca fluviatilis. Sampling sites are represented by blue circles and juxtaposed population names refer to TableS1.

Figure S2 :

 S2 Figure S2: Mitochondrial haplotype networks for each distinct locus as well as for the concatenated alignment of Perca fluviatilis. For each mitochondrial locus as well as for the concatenated alignment, we report the median-joining network and the spatial distribution of haplotypes, i.e. pie charts indicating the haplotypes frequencies identified in each sampling site. In the network, each haplotype is represented by a circle and circle sizes are relative to haplotype frequencies. The number attributed to the line separating two haplotypes represents the number of mutations that differentiates these haplotypes (absence of number corresponding to a single mutation). Red squares on lines represent undetected/extinct intermediate haplotype states. Black circles correspond to P. fluviatilis sequences, empty red circles to P. flavescens sequences, and empty blue circles to P. schrenkii sequences. Each map reports haplotype frequencies in each sampling sites and colors refer to the corresponding haplotype color of the network. Pie chart sizes are relative to the number of individuals analyzed for each sampling site.

Figure S3

 S3 Figure S3 Interpolation of genetic diversity of Perca fluviatilis estimated with the concatenated alignment of mitochondrial sequences (nucleotide diversity π) or with the eight microsatellite markers (Bray-Curtis dissimilarity "BCD") (see the text for further details on the interpolation procedure) for several radius (25, 100, and 200 km).

Figure S4 :Figure S5 :

 S4S5 Figure S4: Majority-rule consensus of the trees sampled by the Bayesian analysis performed on the concatenated molecular data matrix (COI, Cytb, D-loop and 16S) of Perca fluviatilis. Values above branches are Bayesian posterior probabilities/Maximum likehood bootstrap values (only values > 0.5/50 are shown). Posterior probabilities and bootstrap values inferior to 0.95 or 95, respectively, are considered as poorly supported. Color labels of branches refer to geographic areas: yellow for the European Plain Europe, green for Northern and Eastern Europe, brown for the Balkans, and blue for the Danube. P. schrenkii and P. flavescens were used as outgroups to root the trees. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0044848618323640

Figure S6 :

 S6 Figure S6: STRUCTURE HARVESTER results using ΔK method of Evanno et al. (2005) and of log-likelihood values associated with each K ("log(P(K)) method") for Perca fluviatilis

Figure 1 .154Figure 2 .

 12 Figure 1. Barplots representing results obtained for traits studied in phase I for which a statistically significant difference was found between populations (n = 3 per population except for activity and inter-individual distances for which n=9). Different letters indicate significant differences between populations (p-value<0.05) using post-hoc tests. The arrow represents how the expression of each trait should vary to meet stakeholder demands.

  ) and weight (F (3,8) =3.06, p-value=0.09), in final growth heterogeneity for length (F (3,8) =1.26, p-value=0.35) and weight (F (3,8) =0.49, p-value=0.70), and aggressiveness (F (3,8) =2.58, p-value=0.15).

  ribbons (one ribbon corresponding to one female) were obtained during the May 2018 and May 2019 spawning seasons from four lakes (Appendix S1):Valkea-Müstajärvi (VAL; 2018;

  hatching and transferred to three green(RGB: 137, 172, 118) internal-wall 71 L cylindroconical tanks (three replicates per population; RAS) at a density of 50 larvae.L -1 . Photoperiod was 12L:12D (simulation of dawn and dusk for 30 min) and light intensity was 400 lx at the water surface. Temperature was gradually increased during the first two weeks to 20 °C (one °C.day -1 ). Larvae were hand-fed with newly hatched Artemia nauplii (Sep-Art, INVE; seven times a day, every 1h30 from 8.30 am to 5.30 pm) from three days post-hatching until at 16 dph, which corresponds to the beginning of the weaning (i.e. transition from live feed to inert dry artificial diet) period. At 16 dph, Artemia ration was decreased by 25 % every three days and dry feed ration (BioMar, 300 µm until 21 dph, then 500 µm) was increased by the same ratio. After 25 dph, larvae were fed with dry feed ad libitum (BioMar 500 µm, then 700 µm at 44 dph until 60 dph). At 26 dph, the larvae left in the cylindro-conical tanks were removed in order to start phase II.

  using the formula : 100*(Ni-(Nf+Nd+Ns)+Nc)/(Nf-Ns) with Ni the initial number of larvae, Nf the final number of larvae, Nd the sum of dead larvae counted daily, Ns the number of sampled larvae, and Nc the number of truncated or enucleated (enucleation being a specific indicator of aggressiveness in perch; Toomey et al. 2019) larvae among the dead ones (not possible in phase I since it was not possible to count dead larvae during the first five days post-hatching due to fast decomposition; in addition, no truncated or enucleated individuals were recorded for phase I).Regarding the evaluation of inter-individual distances and activity, the detailed protocol is available inToomey et al. (2019). Briefly, for each population, three replicates for each cylindro-conical tank were performed (nine replicates per population) over two days for phase I (25 and 26 dph) and phase II (44 and 45 dph). For each population, 90 individuals (n=30 per cylindro-conical tank, 10 individuals per replicate) were sampled and transferred to three aquaria (58 L; light intensity of 80 lx light intensity, 20 °C). After one night of acclimatization, populations were tested per groups of ten individuals in circular arenas (30 cm diameter, 1.5 cm of water depth, 10 lx) to study inter-individual distances and activity(Toomey et al. 2019). After 30 min acclimatization, individuals were filmed for 30 min. After the experiment, individuals were euthanized (overdose of MS-222) and kept in formalin 4%



  species (see for instance method used in[START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF]; Alvarez-Lajonchère and VAL and ISO belong to the same PU and present similar performances

--

  Divergent conclusions depending on the trait considered e.g. Trait 2: Pop 2 > Pops 1 & 3 Can miss key divergences between populations e.g. Trait 3 Split it up and see: Using proxies to highlight divergent inter-populational performances in aquaculture standardized conditions Under review in Scientific Reports  Specific goal: Assessing if the use of the genetic proxy was the most relevant proxy regarding the larval performance results.

  Ministry of Higher Education, Research, and Innovation (APAFIS13368-2018020511226118, APAFIS17164-2018101812118180). Biological material sampling and aquaculture rearing conditions were adapted from Toomey et al. (2019). Egg ribbons were collected during the spawning seasons across two years (May 2018 and April-May 2019). Seven lakes were sampled (Supplementary Fig. S1) : Valkea-Müstajärvi (VAL; 2018, Finland; 61°13'08"N, 25°07'05"E), Iso-Valkjärvi (ISO; 2018, Finland; 60°57'21"N, 26°13'3"E), Kierzlinskie (KIE; 2019, Poland; 53°47′54″N, 20°44′45″E), Geneva (GEN; 2019, France; 46°22′7.20"N, 6°27′14.73"E), Bourget (BOU; 2019, France; 45°44'12.469"N, 5°52'1.617"E), Hohen Sprenzer (HOH; 2019, Germany; 53°55'10.369"N, 12°13'6.005"E), and Balaton (BAL; 2019, Hungary ; 46°54'23.375"N, 18°2'43.

  ) gene flow disruption/limitation and/or (ii) local adaptation to specific selective pressures, we were expecting that the assessments based on alternative proxies could lead to different results. Indeed, relationships between these two divergence-triggering factors and the alternative proxy-based distance matrices are different. Although larger spatial disjunction (using geographic or hydrologic distance) increases the likelihood to reinforce these divergence-triggering factors (e.g. Wright 1943), interpopulational differentiation can happen between adjacent populations, for instance due to a strong ecological barrier (e.g. for Perca fluviatilis: Bergek and Björklund 2007) or behavioral processes (e.g. natal homing behavior; Carvalho 1993). Detections of such differentiations at small geographic scale are thus unlikely with spatial disjunction a priori (e.g. divergent results between hydrologic and survival rate distance with ISO, KIE, and BAL, see Figshare doi: 10.6084/m9.figshare.11407128).

Figure 9 :

 9 Figure 9: Major developmental events of Perca fluviatilis during larval and juvenile stages according to Kupren et al. (2019).

Figure 10 :

 10 Figure 10: Larva from Lake Geneva at 21 days post-hatching.

Figure 11 :

 11 Figure 11: Comparison of different methods which could be used to classify populations according to their accuracy (i.e. in highlighting populations presenting divergences in key traits) and their feasibility (i.e. pragmatism).

Figure 12 :

 12 Figure 12: Figure illustrating the prioritization of populations for phase I. Pairwise comparisons of populations are plotted (blue squares) according to three proxies (genetic, hydrologic, and habitat distances).

  (e.g.[START_REF] Mckay | Genetic variation for a spinal deformity in Atlantic salmon, Salmo salar[END_REF][START_REF] Afonso | Association of a lordosis-scoliosis-kyphosis deformity in gilthead seabream (Sparus aurata) with family structure[END_REF][START_REF] Gjedrem | Basic statistical parameters[END_REF][START_REF] Friars | Heritability, correlation and selection response estimates of some traits in fish populations[END_REF] Smith 2010;[START_REF] Wang | Heritability and genetic correlation of survival in turbot (Scophthalmus maximus)[END_REF][START_REF] Ødegård | Methodology for genetic evaluation of disease resistance in aquaculture species: challenges and future prospects[END_REF][START_REF] Blonk | Genetic improvement of percids[END_REF][START_REF] García-Celdrán | Estimates of heritabilities and genetic correlations of carcass quality traits in a reared gilthead sea bream (Sparus aurata L.) population sourced from three broodstocks along the Spanish coasts[END_REF][START_REF] Kristjánsson | Heritability of economically important traits in the Atlantic cod Gadus morhua L[END_REF]

Figure 13 :

 13 Figure 13: Hypothetical scenarios regarding the expression of a key trait considered as a facilitating characteristic for domestication/production. Two species are screened, and one population is considered (in blue) for the assessment. In red are represented other conspecific populations'

Figure 14 :

 14 Figure 14: A. Aquaculture potential index formula using the ranking method. B. Aquaculture potential index formula using the standardized values of traits.

Figure 15 :

 15 Figure 15 : Conceptual figure showing the dependency of the identification of units with high aquaculture potential to the specific context (stakeholders' expectations and environmental changes).

Figure 16 :

 16 Figure 16: Conceptual figure regarding the trade-off between risks and advantages in the choice of the founding population(s)

  practices in constituting the founder stock (i.e. sufficient number of breeders;[START_REF] Vandeputte | Quelle gestion génétique de la domestication chez les poissons?[END_REF].Choosing the most suitable populations before starting a selective breeding program was previously highlighted as important to spare generations of within-strain selection[START_REF] Ponzoni | Strain comparisons in aquaculture species: a manual[END_REF], as suggested for instance in European sea bass[START_REF] Vandeputte | Multi-site evaluation of the rearing performances of 5 wild populations of European sea bass (Dicentrarchus labrax)[END_REF][START_REF] Vandeputte | The European sea bass: a key marine fish model in the wild and in aquaculture[END_REF]. The three-step approach appears particularly useful for species which are at the beginning of the domestication process (i.e. first three stages according toTeletchea and Fontaine 2009) and which are a part of the life cycle is performed in captivity (i.e. capture-based productions). For species well advanced in the domestication process, selective breeding programs might be favored (Figure17) rather than starting the process all over again from wild populations.

Figure 17 :

 17 Figure 17: Comparison of the usefulness of the three-step integrative approach and

  large differences in genetic differentiation between Oncorhynchus keta [Actinopterygii, Salmoniformes, Salmonidae], Oncorhynchus clarkii clarkia [Actinopterygii, Salmoniformes, Salmonidae], and Oncorhynchus mykiss [Actinopterygii, Salmoniformes, Salmonidae]; Chevassus 1989), making difficult the extrapolation of the first step conclusions.

  . Local adaptation results from a balance between the homogenizing effect of gene flow and the divergence force of natural selection [i.e. phenotypic differentiation resulting from a genetic composition modification triggered by selective pressures] (Garant et al. 2007; Hauser



  Toomey L, Lecocq T, Bokor Z, Espinat L, Ferincz A, Goulon C, Vesala, S Baratçabal M, Barry M-D, Gouret M, Gouron C, Staszny A, Mauduit E, Mean V, Muller I, Schlick N, Speder K, Thumerel R, Piatti C, Pasquet A, Fontaine P. When the simple way fails: comparison of single-trait and multi-trait approaches to identify best wild populations within a species for aquaculture production. Scientific reports. Under review. Toomey L, Dellicour S, Zarski D, Buhrke F, Fontaine P, Lecocq T. Split it up and see: intraspecific proxies highlighting divergent performances in aquaculture standardized conditions. Scientific reports. Under review. Oral communications  Toomey L, Fontaine P, Lecocq T. Integration of spatial distribution of genetic variability for aquaculture regulations and development, the European perch case. Frontiers in Marine Science. Conference Abstract: XVI European Congress of Ichthyology. September 2 nd -6 th , 2019. Lausanne, Switzerland.  Toomey L, Lecocq T, Fontaine P. Vers une perciculture plus durable et mieux intégrée aux territoires: Intégration de la différenciation intraspécifique dans les programs de domestication. Séminaire SIReNa -Science et Territoire: vers une nouvelle économie. February 7 th , 2019. Nancy, France.  Toomey L, Teletchea F, Fontaine P, Lecocq T. Improving Perca fluviatilis aquaculture by considering population-specific performances in recirculating aquaculture system. European Aquaculture Society -AQUA2018. August 25th-31st, 2018. Montpellier, France.  Lecocq T, Toomey L, Fontaine P. Defining units with high potential for aquaculture within species -Towards an integration of intraspecific differentiation in fish domestication programs. European Aquaculture Society -AQUA2018. August 25 th -31 st , 2018. Montpellier, France.  Rocha De Almeida T, Alix M, Schaerlinger B, Le cam A, Montfort J, Toomey, L Bobe J, Chardard D, Fontaine P. A transcriptomic comparison suggests an influence of the domestication process on egg quality in Eurasian perch (Perca fluviatilis).OTHER ACTIVITIES DURING THE PhD Teaching experience: I got the opportunity during my PhD to teach bachelor students (first to third year bachelor). During the first two years, I contributed to teach practical classes in zoology (total of 86h over the two years). This experienced allowed me to improve my presentation skills and to acquire competences in educational methods. In order to start my fourth PhD year, I started a part-time teaching contract (October 2019 -to date) which allowed me to diversify my teaching topics (zoology, evolutionary biology, functional diversity, behavioral ecology; 132 hours).  Mentoring experience: I supervised 13 students between 2018 and 2019, from third year bachelor to second year Master students. This experience improved my supervision skills and rigor in explaining and planning experiments.

  pêche n'était donc plus suffisante pour répondre à la demande. L'aquaculture s'est alors développée et c'est un des secteurs alimentaires qui a connu une des croissances les plus rapides de ces dernières décennies. Actuellement, l'aquaculture fournit plus de la moitié des produits aquatiques qui sont consommés au niveau mondial. Toutefois, la production aquacole se base à l'heure actuelle sur peu d'espèces. En effet, 85% de la production aquacole repose sur seulement 15 espèces. Cela pose plusieurs problèmes, socioéconomiques et environnementaux, qui se traduisent par une faible résilience du secteur aquacole. De nos jours, il existe une volonté de développer une aquaculture plus durable.L'une des voies prometteuses pour promouvoir la durabilité du secteur de l'aquaculture repose sur la diversification de la production, notamment par la domestication et la production de nouvelles espèces.La domestication correspond au processus par lequel des populations sont élevées et reproduites dans un environnement contrôlé par l'Homme et modifiées au fil des générations par rapport à leurs ancêtres sauvages dans un objectif de les rendre plus utiles pour l'Homme qui contrôle durant l'ensemble du processus leur reproduction et leurs apports alimentaires. Contrairement aux espèces terrestres, la domestication des espèces aquatiques est beaucoup plus récente et la volonté de diversification de la production mène à de nombreux essais de domestication de nouvelles espèces. Cependant, la domestication et la production de nouvelles espèces sont des processus longs et difficiles qui peuvent échouer en raison de défis techniques, de limitations socio-économiques ou de caractéristiques propres aux espèces. L'identification de ces caractéristiques (biologiques et socio-économiques) a permis de développer des approches pour sélectionner de nouvelles espèces candidates à la domestication. Cependant, ces approches ne prennent pas en compte le fait que certaines de ces caractéristiques peuvent également varier au niveau intraspécifique. En effet, la différenciation géographique (différenciation entre populations conspécifiques allopatriques) peut façonner des spécificités génétiques, phénotypiques et écologiques, ce qui pourrait entraîner des prédispositions différentielles à la domestication ou différents attraits socio-économiques entre populations allopatriques.Une différenciation géographique a déjà été démontrée entre populations allopatriques sauvages pour des traits clés (par exemple : taux de croissance, taux de survie, taux d'agressivité) et pour de nombreux taxons. Par conséquent, le choix d'une ou de plusieurs populations sauvages présentant un potentiel élevé pour l'aquaculture (c'est-à-dire présentant une expression intéressante des traits clés) pourrait permettre de faciliter la domestication et la production de nouvelles espèces. Toutefois, les spécificités observées dans le milieu sauvage pourraient ne pas être conservées dans les conditions d'élevage. En effet, l'expression des traits pourrait changer dans l'environnement d'élevage car ces traits, comme tout trait phénotypique, sont façonnés par la divergence génétique et l'environnement. Or, les conditions environnementales en milieu d'élevage peuvent être très différentes du milieu sauvage, particulièrement dans des systèmes d'élevage intensifs. Par conséquent, seules les différenciations phénotypiques qui sont façonnées par des divergences génétiques présentent un intérêt pour la domestication. Afin d'évaluer la différenciation d'expression de traits entre populations allopatriques, des expériences en common-garden (« jardincommun ») sont donc nécessaires, qui permettent la comparaison de populations dans un même environnement d'élevage. En effet, comparer les populations dans le même environnement permet d'éliminer les effets dus à l'environnement. En conséquence, une différenciation d'expression de traits en common garden sera attribuée à des différenciations génétiques. Néanmoins, (i) il n'est pas possible en pratique de comparer l'ensemble des populations d'une espèce à travers son aire de répartition géographique et (ii) la sélection aléatoire de populations pour des expériences common garden pourrait mener à ne pas évaluer des populations qui présentent un fort potentiel pour l'aquaculture. De plus, l'attention est souvent portée sur un seul trait biologique (souvent le taux de croissance et/ou la qualité du produit) ou une fonction biologique précise lors du processus de domestication. Or, la capacité à être domestiqué et produit dépend d'un ensemble de traits liés à plusieurs fonctions biologiques (ex : croissance, développement, reproduction, immunité, comportement). Il est donc nécessaire de définir un ensemble de traits clés qu'il est nécessaire d'évaluer pour étudier le potentiel pour l'aquaculture (potentiel d'une population à être domestiquée et produite avec succès) à l'échelle intraspécifique. Par conséquent, le développement d'une méthodologie est nécessaire pour prendre en compte la différenciation géographique dans la domestication de nouvelles espèces. Cette méthodologie se veut pragmatique et générique pour être applicable à tout nouveau processus de domestication. Cette thèse vise à : (i) Evaluer si la différenciation géographique peut être utile dans la domestication/production de nouvelles espèces chez une espèce cible. (ii) Conceptualiser et mettre en application une méthode pragmatique et standardisée pour intégrer la différenciation géographique dans les processus de domestication. L'approche développée a été testée sur une espèce d'intérêt pour la diversification de l'aquaculture continentale: la perche européenne (Perca fluviatilis) et les premiers stades de vie (nurserie). Le premier chapitre de la thèse vise à évaluer si P. fluviatilis présente une différenciation géographique pour des traits clés pour l'aquaculture. Une différenciation géographique a été précédemment mise en évidence pour des traits liés à la croissance et à la survie. Toutefois, la domestication est également influencée par d'autres traits, comme des traits comportementaux. Ce chapitre est donc axé sur des traits comportementaux des larves et nous avons démontré l'existence d'une différenciation géographique pour les interactions agressives et la structure de groupe entre trois populations allopatriques de P. fluviatilis. Ces résultats ont mis en évidence l'utilité de considérer la différenciation géographique pour la domestication/production de la perche commune. Le deuxième chapitre vise à conceptualiser l'approche intégrative pour considérer la différenciation géographique dans le processus de domestication. Ce chapitre présente dans un premier temps le contexte lié à la diversification et la domestication de nouvelles espèces ainsi que l'intérêt de prendre en compte la différenciation géographique. Puis, la méthode proposée est présentée. Elle se compose de trois étapes : (i) la classification des populations sauvages en unités prospectives (c'est-à-dire en groupes de populations différenciées) qui présentent des chances d'être divergentes pour des traits clés en aquaculture, (ii) l'évaluation des performances des différentes unités prospectives dans des conditions d'élevage standardisées (common garden) à travers une approche multifonction et multi-trait, et (iii) l'identification d'une (des) unité(s) prospective(s) ayant le plus grand potentiel pour l'aquaculture à travers la pondération des différents traits et l'utilisation d'un score qui permet la synthèse des résultats obtenus dans l'approche multi-trait. Les chapitres suivants ont permis de mettre en application cette méthode sur les premiers stades de vie de P. fluviatilis. Le troisième chapitre vise à établir une classification intraspécifique de P. fluviatilis (c'est-à-dire une classification des populations sauvages en unités prospectives). Comme première approche, nous avons choisi de réaliser une étude phylogéographique puisque des groupes de populations ayant des histoires démographiques divergentes sont susceptibles d'avoir acquis certaines spécificités phénotypiques, notamment par des processus d'adaptation locale. Ces groupes de populations pourraient présenter des potentiels divergents pour l'aquaculture. A travers le séquençage de quatre marqueurs mitochondriaux, nous avons identifié cinq unités prospectives: Plaine européenne, Danube, nord et est de la Fennoscandie, Europe de l'Est et Balkans. Cette classification est corroborée par l'utilisation de marqueurs microsatellites qui mène à une subdivision de ces cinq unités prospectives. En plus de présenter une classification intraspécifique, ces résultats ont été utilisés pour suggérer des pistes pour la conservation et la gestion des populations sauvages. Enfin, des similarités entre différenciation génétique et différenciation comportementale (chapitre 1) ont pu être mises en évidence. Le quatrième chapitre vise à évaluer les performances de trois des cinq unités prospectives pour les premiers stades de vie de P. fluviatilis dans des conditions d'élevage standardisées (common garden). Quatre populations allopatriques ont été étudiées, dont deux appartenant à la même unité prospective. Ce chapitre vise à comparer l'utilité des approches mono-trait et multi-trait pour identifier les unités à fort potentiel aquacole. Nos résultats ont montré que l'approche mono-trait peut (i) mener à négliger des différenciations inter-populationnelles pour d'autres traits que celui considéré et (ii) mettre en évidence différentes populations d'intérêt en fonction du trait considéré. En revanche, l'approche multi-trait permet d'établir un consensus entre tous les traits et d'identifier la population ayant le plus fort potentiel aquacole grâce à l'élaboration d'un score de potentiel aquacole. Outre l'intérêt de l'approche multi-trait, ce chapitre a également permis de mettre en évidence (i) une forte différenciation géographique entre populations/unités prospectives, (ii) une similarité des performances de deux populations appartenant à la même unité prospective (différenciation intra-unité), et (iii) des convergences entre différenciation génétique et différenciation géographique. Le cinquième chapitre vise à évaluer si le proxy génétique utilisé pour la première étape de la classification était la bonne approche. Nous avons évalué la pertinence de trois proxies alternatifs pour mettre en évidence les divergences inter-populationnelles pour des traits clés pour la larviculture : (i) la distance génétique, (ii) la divergence des habitats et (iii) les distances géographiques/hydrologiques. Cette étude a été effectuée à partir des résultats acquis sur les performances de sept populations allopatriques de perche commune. Nos résultats ont révélé des différences dans le degré de corrélation entre les matrices de distance basées sur les proxies alternatifs et les matrices de distance basées sur les traits clés. La distance génétique est le proxy corrélé au plus grand nombre de traits clés. Cependant, aucun proxy n'est corrélé à toutes les matrices de distance des différents traits. Par conséquent, nous suggérons comme méthode alternative pour la première étape d'utiliser une approche multi-proxy associée à une hiérarchisation des populations. La hiérarchisation des populations permettra d'identifier les unités biologiques qu'il faut considérer pour la deuxième étape de l'approche intégrative. Dans la discussion, les biais expérimentaux, les limites et les améliorations potentielles sont passées en revue pour chaque étape de la méthode intégrative ainsi qu e les implications pour la larviculture de perche commune. En effet, la population du lac Balaton présente le potentiel pour l'aquaculture le plus élevé mais ces résultats sont néanmoins spécifiques au système d'élevage utilisé. Dans un deuxième temps, l'applicabilité de la méthode est discutée en termes de répétabilité, faisabilité et généricité. Les facteurs de risque et les précautions à prendre sont également abordés ainsi que les différents scenarios d'applicabilité de la méthode. Enfin, dans une dernière partie sont abordées les différentes perspectives quant au devenir des unités biologiques utilisées ainsi qu'une éventuelle détermination de l'origine des différenciations géographiques démontrées dans cette thèse.

Table 1 :

 1 Examples of alternate domestication definitions referenced in literature.

Table 2 :

 2 Domestication levels according to

Table 9 :

 9 Previous studies having investigated Perca fluviatilis genetic differentiation.

Table 10 :

 10 Example of rearing conditions used in literature for European perch larviculture.

	Dph: days-post hatching; NA: not available.

Table 11 :

 11 Rearing parameters used for the bioassays.

Table 12 :

 12 Summary of sampling, transport, and incubation of egg ribbons for the different populations. Development stages refer to

Table 1 :

 1 Examples of alternate domestication definitions referenced in literature.

Table 4 :

 4 Examples of characteristics which favor fish domestication and production[START_REF] Liao | Methodological approach used for the domestication of potential candidates for aquaculture. Recent advances in Mediterranean aquaculture finfish species diversification -Cahiers Options[END_REF][START_REF] Diamond | Evolution, consequences and future of plant and animal domestication[END_REF][START_REF] Jobling | Farmed species and their characteristics[END_REF][START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF], associated to examples of wild geographic differentiation for these characteristics.

Table 5 :

 5 Examples of the main traits/parameters investigated in the geographic differentiation studies referenced.

	Biological function/Other traits	Main traits/Parameters investigated
	Growth & product quality	Length, weight, growth heterogeneity, body shape, color, fillet yield, lipid content/fatty acid content, protein content, slaughter weight, liver weight, gutter weight, biomass gain
	Development	Cleavage status, swim bladder inflation rate, deformity rate, sex ratio
		Boldness, shoaling, aggressiveness (sometimes more specifically
	Behavior	cannibalism rate), activity, anti-predator behavior, foraging, courtship
		activeness in males
	Immunity	Susceptibility to various diseases/parasites
		Food intake, feed conversion efficiency, feed conversion ratio, yolk sac
	Feeding	utilization, total digestibility, relative nitrogen digestibility, passage time,
		digestion rate

INTRODUCTION 36 6. How can geographic differentiation be useful for fish domestication?

Table 5

 5

	), it has been overall poorly

considered later in the domestication process, for selective breeding programs (stage five of the domestication process; Teletchea and Fontaine 2014). A few success stories show the interest of using geographic differentiation at more advanced stages of domestication (i.e. selective breeding programs). The most striking example is the Atlantic salmon (Actinopterygii, Salmoniformes, Salmonidae, Salmo salar) domestication. A family breeding program started in the 1970's in Norway which aimed at improving the Atlantic salmon production. Eggs were sampled from 40 Norwegian rivers and one Swedish

Table 6 :

 6 Examples of studies highlighting trait differentiation between Salmo salar allopatric populations. Remark: These studies did not all perform an evaluation on all 41 populations but rather on a subset of populations.

Table 8 :

 8 Studies highlighting Perca fluviatilis geographic differentiation in aquaculture conditions.

	Remark: Only traits for which a geographic differentiation was shown are reported here. Rivers,
	lakes, brackish waters, and ponds are indicated by R, L, B, and P, respectively.
	Study	Populations studied	Life stage	Traits investigated
		Four populations from Italy
		(L), northwest France (P), southeast France (P),	Larvae	Survival, body weight, specific growth rate
		Belgium (R)
	Mandiki	Three populations from		Survival, cannibalism rate,
	et al.	Belgium (R), Finland (B),	Small juveniles	body weight, specific growth
	(2004)	Poland (L)		rate, feed efficiency
		Three populations from		Body weight, specific growth
		Belgium (R), Finland (B),	Large juveniles	rate, feed efficiency, feed
		Poland (L)		consumption
	Pimakhin and Zak (2014)	21 populations from Poland (R and L), Czech Republic (R), Germany (L), Bulgaria (L), Finland (L), Slovakia (L)	Larvae & juveniles (14 to 56 days post-hatching)	Swim bladder inflation, weight
	Vanina et	Three populations from	Larvae & juveniles	Body weight, specific growth
	al.	Czech Republic (P), Slovakia	(31-115 days post-	rate, mortality rate, growth
	(2019a)	(R), and Poland (L)	hatching)	heterogeneity
	Vanina et al. (2019b)	Seven populations: Finland (L), Poland (L and B), Czech Republic (P), Slovakia (L and R)	Larvae (three to 24 days post-hatching)	Survival rate of embryos, egg diameter, body weight, total length, specific growth rate

Table 9 :

 9 Previous studies having investigated Perca fluviatilis genetic differentiation

	Article	Sampling site(s)	Genetic structure?	Marker(s)
	Gerlach et al. (2001)		Two populations differentiated	Microsatellites
	Heldstab and Katoh (1995)		Differentiated from lakes Maggiore Zürich, Geneva, and	Allozymes *
			No differentiation within
		Lake Constance (Germany)	Lake Constance or with the
	Behrmann-Godel		Rhine river. Differentiation	Mitochondrial
	et al. (2004)		between Lake Constance	D-loop
			and Rhine river with lakes
			Walensee and Zürich
	Behrmann-Godel et al. (2006)		Differentiation between kin shoals	Microsatellites
	Ben Khadher et al. (2015)	Lake Geneva (Switzerland)	No differentiation	Microsatellites
	Ben Khadher et al. (2019)	Lakes Geneva (Switzerland) & Neufchâtel (France)	Differentiation between the two lakes	Microsatellites
	Gyllensten et al. (1985)	Five brackish water areas and Scotland, Sweden, Finland) eight freshwater areas (Ireland,	No differentiation	Allozymes
	Bergek and Björklund (2009)		Strong differentiation	Microsatellites
	Olsson et al. (2011)	Baltic Sea (Sweden)	Differentiation between gulf central Baltic and Bothnia	Microsatellites
	Bergek et al. (2010)		Differentiation along an environmental gradient	Microsatellites
	Demandt (2010)	Biotest basin (Sweden)	Differentiation	Microsatellites
	Bergek and
	Björklund (2007); Bergek and	Lake Erken (Sweden)	Differentiation	Microsatellites
	Olsson (2009)
	Faulks et al. (2015)	Lakes Bysjön, Dagarn, Fiolen, Stora Envättern, & Stensjön (Sweden)	Within each lake, populations differentiation between pelagic and littoral	AFLP **
	Nesbø et al. (1998a)	Lake Anjersjön, Bothnia Gulf, Rovagen peninsula, Ängeran river (Sweden)	Differentiation	Mitochondrial D-loop and AFLP
	Refseth et al. (1998)	Baltic sea & Scandinavian peninsula (Norway, Sweden)	Differentiation	Mitochondrial and minisatellites ***
	Sruoga et al. (2008)	Baltic sea & Curonian Lagoon (Lithuania)	No differentiation	Microsatellites
	Butkauskas et al. (2012)	Lakes Drūkšiai, Plateliai, Metelys, & Nemunas and Neris rivers (Lithuania)	Lake Drūkšiai differentiated from other populations	Mitochondrial D-loop
	Ragauskas et al.	19 Baltic sea populations	Four groups genetically	Mitochondrial
	(2020)	(Lithuania, Latvia, and Belarus)	differentiated	D-loop
	Kokina et al. (2018)	Lakes Kala & Babites (Latvia)	Low genetic differentiation	Microsatellites

Table 10 :

 10 Example of rearing conditions used in literature for European perch larviculture. Dph: days-post hatching; NA:

not available Article Age Tank shape Inner tank color Tank volume Water renewal rate Density (larvae/L) Temperature (°C) Photoperiod (L:D) Luminosity (lx) Feeding protocol

	Tamazouzt et al. (2000)	1 to 15 dph	Cylindro-conical	Black, light grey, dark grey, white	100 L	20 % /day	10	19,7 -21,6	14:10	250, 400, and 800	1 to 3 dph: zooplankton. 4 dph: dry feed, 6 times/day
	Kestemont et al. (2003)	1 to 21 dph 22 to 44 dph	Rectangular or cylindro-conical Rectangular or cylindro-conical	NA NA	25-100 L 25-100 L	NA NA	10, 32, or 100 1, 3.2, or 10	17, 20, or 23 23	8:16, 12:12, 16:8, or 24:0 8:16, 12:12, 16:8, or 24:0	5, 30, 90, or 400 5, 30, 90, or 400	Artemia between 3 and 21 dph, weaning for seven days. Different feeding ratios: 1%, 5%, 10%, 20% biomass/day Different weaning strategies: 100:0, 99/1, 95/5 (dry feed/Artemia).
	Babiak et al. (2004)	1 to 84 dph	NA	NA	60 L, then 120 L after 50 dph	NA	20 -40 or 200	Incubation: 13, after 1 dph: 17.6	NA	NA	Artemia nauplii between 9am and 7pm, weaning from 14 pdh, dry feed exclusively after 37 dph
	Jentoft et al. (2006)	1 to 35 dph	Rectangular	Black or grey	100 L	1 L/min	23	Incubation at 11.1, then 16	24:0	100-150	Artemia for four weeks then weaning
	Król et al. (2015)	10 to 87 dph	NA	NA	1000 L for hatching then 30L at 10 dph	NA	50	Incubation at 17, then 22	16:8	NA	Artemia between 4 and 11 dph (6 times a day), then weaning, and dry feed exclusively after 22 dph (5 times a day)
	Król et al. (2019)	1 to 33 dph	NA	NA	500 L	NA	NA	Incubation at 14, before hatching 17, then rise to 21	16:8	75	From 5 to 15dph Artemia and fry feed6 times a day. Then only dry feed.
	Palińska-Żarska et al. (2019)	1 to 20 dph	NA	White / Black	50 L	NA	60 / 500	Incubation at 14, then 15 / 20 / or 25	24:0	100 during incubation, then 1500	Artemia two times a day from 5 dph
	Vanina et al. (2019b)	1 to 24 dph	Rectangular	Light grey	200 L until 3 dph then 60 L	1 L/min	67 after 3dph	Incubation at 17, then 23	12:12	200-250	Artemia from 3 dph, weaning between 21 and 24 dph

Table 11 :

 11 Rearing parameters used for the bioassays.

	Incubation	Phase I:

1 dph to 26 dph Phase II: 27 dph to 60 dph

		Incubators
	Experimental structure	(110x64x186 cm) containing nine racks each	Green (RGB: 137, 172, 118) internal-wall 71 L cylindro-conical tanks	Green (RGB: 137, 172, 118) internal-wall 71 L cylindro-conical tanks
		(45x7x12 cm)
	Flow renewal	4 m 3 .h	-1	-1 16 dph to 26 dph: 50 %.h 1dph to 15 dph: 25 %.h -1	75 %.h	-1
	Temperature	13 °C	13 to 20 °C	20 °C
	Photoperiod	12:12	12:12	12:12
	Density	1-4 ribbon(s) / crate	50 larvae / L	19 larvae / L
	Light
	intensity at	400 lx	400 lx	80 lx
	water surface
				Artemia nauplii from 3 dph,
				seven times / day (8.30 am to
				5.30 pm)
				From 16 dph: weaning for nine	Dry feed, seven times a
	Feeding	-		days (25% decrease of Artemia every three days, increase of	day (8.30 am to 5.30 pm). BioMar 500 µm, then 700
				dry feed in the same	µm at 44 dph until 60 dph
				proportions)
				Dry feed: BioMar, 300 µm
				until 21 dph, then 500 µm

  After 1h, individuals were euthanised with an overdose of MS-222 following European rules and kept in formalin 4% for later length measurements. Larvae tested from ISO, VAL and GEN were respectively 14.05 ± 0.55mm, 12.90 ± 0.62mm, and 13.87 ± 0.26mm. This full experiment was performed again during experiment II with fish sampled from cylindro-conical tanks at 44 and 45 dph. For this second

test, individuals from

ISO, VAL and GEN were respectively 26.74 ± 1.67mm, 26.28 ± 1.99mm, and 22.97 ± 1.08mm

(no statistical difference between populations for the two experiments; experiment I: F=0.712, df=2, P=0.528; experiment II: F=1.68, df=2, P=0.263).

  Fontaine 2014) ranging from the first trials of acclimatization (level one) in the culture environment to the life cycle completion in captivity (levels three and four) and, eventually, to the selective breeding program setting up (level five). It is a long and tough process and attempts are often unfruitful[START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]. Indeed, previous domestication attempts on new species show that such tries often lasted only a few years before being

abandoned

[START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF][START_REF] Metian | Mapping diversity of species in global aquaculture[END_REF]

. Furthermore, even when the life cycle is completed in captivity, major bottlenecks can still remain, impeding domestication continuation and production development

[START_REF] Teletchea | Levels of domestication in fish: Implications for the sustainable future of aquaculture[END_REF]

. Such failures and issues result from the inability of domestication programs to meet challenges of initiating domestication process (i.e. acclimatization), completing lifecycle, and overcoming major bottlenecks (i.e. very low survival rate) due to technical limitations, economic constraints, or some intrinsic species traits (i.e. single feature or quantifiable measurement of an organism; Jobling 2010). These latter are for instance low growth rate, sensitivity to disturbances or diseases, or high aggressiveness, which characterize poor candidates for domestication

  Toomey et al. 2019), immunity (e.g.Glover et al. 2003), and stress sensibility (e.g.[START_REF] Delabbio | Variation in growth and survival between two anadromous strains of Canadian Arctic charr (Salvelinus alpinus) during long-term saltwater rearing[END_REF]). Therefore, considering wild geographic differentiation when starting new fish domestication programs could unlock population-specific potential included in the wild intraspecific biodiversity.

Besides the obvious choice of populations with the highest aquaculture potential to start domestication programs, differentiated populations can display specificities that could allow overcoming current bottlenecks in species at intermediate domestication levels (i.e. level four; e.g. the aquaculture of Perca fluviatilis, a species facing strong bottlenecks in its development due to a low larval survival rate and high deformity rate;

[START_REF] Fontaine | Domestication of the Eurasian Perch (Perca fluviatilis)[END_REF]

Table 1 : Set of traits considered in the integrative approach in the context of monoculture in RAS and ponds for the consumption market.

 1 Category 1 includes biological traits measured on a group of individuals of the target prospective unit which reflect the fitness (i.e. ability to survive, grow and reproduce) in captive conditions. Category 2 includes biological traits which are specifically relevant to a production system (e.g. RAS, pond, raceway) and/or a specific production goal (e.g. fillet, whole fish sale). Category 3 includes biological traits linked to the interaction between the group of individuals and the rearing system, which could impact surrounding environments. Category 4 includes biological traits relative to future major challenges and disturbances. Traits in italic correspond to traits less important according to Percid and Sturgeon farmers (less than 50% of opinions considering the trait as quite important or important for at least one or both species groups).

	Category	Sub-category	Trait group	Trait
				Breeder survival rate
			Breeders	Age and size at sexual maturity
				Fecundity
				Volume of sperm
			Gametes	Number of oocytes
				Number of spermatozoids
		Reproduction		Survival rate
				Egg diameter
			Fertilized eggs	Malformation rate
				Fertilization rate
				Hatching rate
			Spawning	Spawning timing Spawning duration
	Category 1		Growth	Growth rate Growth heterogeneity Volume of the yolk sac
			Nutrition	Larvae size at hatching Timing for the exogenous feeding
		Larviculture		transition Swim bladder inflation rate
			Development	Deformity rate
				Survival rate
				Cannibalism rate
			Aggressive behavior	Age at cannibalism onset
				Size at cannibalism onset
			Growth	Growth rate Growth heterogeneity
		On-growing	Development	Sex-ratio Survival rate
			Nutrition	Food conversion ratio
		Intensive	Traits involved in response	Resistance to sub-lethal stress and
	Category 2	monoculture	to captive environment	diseases/parasites which are
		in RAS -	pressures	expectable in RAS environment

  ; Østbye et al. 2005). However, P. fluviatilis displays high genetic variability in eastern Europe, Fennoscandia, and central Europe while most European freshwater fish species have their genetic variability hotspots in southern Europe (e.g.[START_REF] Durand | Phylogeography and postglacial dispersion of the chub (Leuciscus cephalus) in Europe[END_REF][START_REF] Gum | Mitochondrial and nuclear DNA phylogeography of European grayling (Thymallus thymallus): evidence for secondary contact zones in central Europe[END_REF] but see[START_REF] Kotlík | Phylogeography of the barbel (Barbus barbus) assessed by mitochondrial DNA variation[END_REF].

  fluviatilis aquaculture is a major challenge for fish farmers since they are facing several bottlenecks which are limiting P. fluviatilis economic development such as low survival and growth rates, high growth heterogeneity, cannibalism, or low egg quality

(Kestemont et al. 2015a

). Moreover, genetic diversity is also a limiting factor in breeding programs since it can lead to inbreeding depression

[START_REF] Boissy | Genetics of adaptation and domestication in livestock[END_REF]

. One solution to overcome current issues consists in (i) sampling individuals to create fish farmers stocks in genetic diversity hotspots and (ii) taking into account variation of zootechnical traits between geographically distinct populations of the European perch. Indeed, this latter could be potentially relevant since variations in traits related to growth (e.g. growth rate, growth heterogeneity rate), development (e.g. swim bladder inflation rate, survival rate), organoleptic characteristics (e.g. color, filet quality), and behavior (cannibalism rate, group structure) have been highlighted in P. fluviatilis

Table S3 : Best-fitting substitution models identified with jModeltest for the different genes and the concatenated mitochondrial alignment of Perca fluviatilis

 S3

	Locus	16S	COI	CytB	D-Loop	Concatenated matrix
	Sequence length (bp)	541	641	399	312	1893
	Number of variable sites	10	23	18	7	58
	Number of haplotypes	11	22	16	7	64
	Haplotype diversity	0.32	0.73	0.59	0.40	0.83
	Nucleotide diversity	0.00048	0.0030	0.0023	0.0025	0.0021
	G ST	0.56 *	0.57 *	0.53 *	0.49 *	0.43 *
	N ST	0.61 *	0.62 *	0.42 *	0.62 *	0.58 *
	N ST -G ST	0.05 *	0.04 *	-0.10	0.13 *	0.14 *
	Global Φ ST for K=1	0.60 *	0.63 *	0.43 *	0.62 *	0.58 *
	Locus		Best fitting model	MrBayes substitution model
	16S		K80			-
	COI 1 st		GTR			-
	COI 2 nd		TVM			GTR
	COI 3 rd		TIM1+G			GTR+G
	Cytb 1 st		TVM+I			GTR+I
	Cytb 2 nd		TrN+I			GTR+I
	Cytb 3 rd		GTR			-
	D-Loop		TIM1+I			GTR+I
	Concatenated matrix		TPM3uf+I+G		GTR+I+G

. Locus corresponds to the gene or the concatenated matrix according to codon position for coding genes

(COI and Cytb)

. Best fitting model corresponds to the model found using jModeltest with the Akaike information criteria corrected for small sample sizes. MrBayes substitution model corresponds to the closest over-parameterized model available.

Locus corresponds to the gene or the concatenated matrix according to codon position for coding genes

(COI and Cytb)

. Best fitting model corresponds to the model found using jModeltest with the Akaike information criteria corrected for small sample sizes. MrBayes substitution model corresponds to the closest over-parameterized model available.

Table S4 : Properties of the eight microsatellite loci of Perca fluviatilis used in this study

 S4

	Table									. A:
	number of alleles per locus; Ar: allelic richness, Ho and He: observed and expected (He)
	heterozygosities.
										Total over
		Svi17	PflaL2	SviL7	PflaL4 YP111 PflaL6	YP60	PflaL1	loci and
										populations
	A	40	35	28	22	14	18	19	23	-
	Ar	4.06	4.39	3.87	4.01	2.67	2.72	3.87	3.52	-
	Ho	0.563	0.701	0.467	0.535	0.557	0.577	0.618	0.534	0.569
	He	0.657	0.668	0.630	0.653	0.500	0.476	0.627	0.611	0.603
	A: number of alleles per locus; Ar: allelic richness, Ho and He: observed and expected (He)
	heterozygosities.

  At the end of the experiment, larvae were euthanized with an overdose of MS-222 for further length measurements. Mean total lengths of larvae tested from VAL, ISO, KIE, GEN, BOU, HOH, and BAL were respectively 12.90 ± 0.62 mm, 14.05 ± 0.55 mm, 10.90 ± 0,73 mm, 11.81 ± 1.01 mm, 11.77 ± 0.48 mm, 11.35 ± 0.72 mm, and 10.62 ± 0.47 mm. Images were extracted from videos every five minutes (six images per video) to evaluated inter-individual distances (i.e. mean of distances between a focal individual and all the other individuals of the group; group cohesion indicator; Buske

Table 1 :

 1 Multi-regression (MRDM) and commonality analyses (CA) results after having successively removed all suppressors (Supplementary TableS1). Analyses were performed between each TIAbased distance matrix (response variable) and all proxy-based (genetic distance, habitat divergence,

	geographic distance and hydrologic distance proxies) distance matrices. With: Pearson's correlation
	coefficient (r), β weights (β), and unique (U) and common (C) contributions of proxies to the variance
	of the response variable. (*) indicates significant R 2 associated with a p-value<0.05 (after Benjamini-
	Hochberg correction).

Table 12 :

 12 Summary of sampling, transport, and incubation of egg ribbons for the different

	populations. Development stages refer to Alix et al. (2015). O1: first phase of organogenesis (from the
	first cell differentiation to the first heart beatings; 2-4 days post-fertilization); O2: second phase of
	organogenesis (from the first heart beatings to the differentiation of the organs associated to the
	digestive system; 4-7 days post-fertilization).
	Lake	Country	Sampling year	Time between sampling and incubation	Transport mode	Development stage at arrival	Number of ribbons used
	Valkea-Müstajärvi	Finland	2018	23h	Plane + car	Early O2	19
	Iso-Valkjärvi	Finland	2018	25h	Plane + car	Early O2	19
	Geneva	France	2019	14h	Car	Early O1	15
	Bourget	France	2019	7h	Car	Late O2	16
	Hohen Sprenzer	Germany	2019	20h	Car	Mid O2	20
	Kierzlinskie	Poland	2019	15h30	Car	Late O1	32
	Balaton	Hungary	2019	14h30	Car	Early O2	13
	Ribbons of very bad quality (i.e. fragmented egg ribbon, low egg survival at eyed-stage;
	Schaerlinger and Żarski 2015) or unsynchronized (with the majority of other egg ribbons) in
	terms of embryo development (according to the development table in

Table 13 :

 13 Univariate statistics results on differentiation between populations and prospective units (PU) for the different traits studied.  indicates a statistically significant differentiation (p-value<0.05), a cross (x) indicates a lack of statistically significant differentiation (p-value>0.05). Diff corresponds to differentiation. Mean value corresponds the mean across all populations/PUs, minimum to the lowest value, maximum to the maximal value.

	Phase	Biological function	Trait	Diff ?	Populational level Mean value (Minimum-Maximum)	Diff ?	PU level Mean value (Minimum-Maximum)
			All traits combined		-		-
			SGR length		2.98 %.day -1 (2.32-3.41)	x	2.93 %.day -1 (2.72-3.11)
		Growth	Initial length Final length	 	6.20 mm (5.77-6.76) 13.40 mm (12.39-14.83)	 x	6.15 mm (5.77-6.56) 13.16 mm (12.47-13.67)
			Final length heterogeneity	x	1.77 % (1.27-2.44)	x	1.74 % (1.40-2.14)
	I	Other Development	Survival rate Deformity rate Swim bladder inflation rate	  	32.77 % (13.11-62) 3.82 % (0.56-8.96) 57.87 % (42.81-93.29)	  	40.39 % (24.53-62) 2.56 % (0.60-6.01) 68.14 % (44.79-93.29)
		Nutrition	Yolk sac volume		1.79 mm 3 (0.20-4.50)		1.45 mm 3 (0.36-2.53)
			Global aggressive rate	x	0.03 % (0-0.10)	x	0.02 % (0-0.06)
		Behavior	Activity		1.33 cm.s -1 (1.09-1.70)		1.41 cm.s -1 (1.26-1.65)
			Inter-individual distances		12.99 cm (11.71-14.48)		13.49 cm (12.09-14.24)
			All traits combined		-		-
			SGR length	x	3.05 %.day -1 (2.71-3.30)	x	3.09 %.day -1 (2.94-3.30)
			SGR weight	x	10.14 %.day -1 (8.89-11.15)	x	10.31 %.day -1 (9.75-11.14)
			Initial length		12.85 mm (10.88-14.74)		12.94 mm (11.02-14.70)
		Growth	Final length Initial weight	 	33.20 mm (25.93-33.80) 17.90 mg (10.20-28.52)	 	33.63 mm (27.47-37.65) 12.84 mg (11.02-14.90)
			Final weight		396.90 mg (203.77-584.66)		409.09 mg (239-518.25)
	II		Final length heterogeneity	x	1.51 % (1.04-1.82)	x	1.54 % (1.37-1.67)
			Final weight heterogeneity	x	0.86 % (0.73-1.16)	x	0.84 % (0.73-0.95)
		Other	Survival rate		26.27 % (13.17-35.30)		27.20 % (15.68-34.07)
		Development	Deformity rate Swim bladder inflation rate	 	1.87 % (0.31-6.16) 75.64 % (36.66-95.35)	x 	1.61 % (0.31-3.50) 77.74 % (53.22-91.75)
			Global aggressive rate	x	19.58 % (10.92-26.36)	x	18.14 % (10.96-25.87)
		Behavior	Activity		1.60 cm.s -1 (0.74-3.38)	( n=4)	1.85 cm.s -1 (0.83-3.38)
			Inter-individual distances		11.56 cm (10.12-12.53)	 (n=4)	11.47 cm (10.12-12.53)

Table 16 :

 16 Calculation of the aquaculture potential score using formulas A and B and data from the fourth chapter.

		Formula A	Formula B
	Population	Aquaculture	Interest for	Aquaculture	Interest for
		potential score	domestication	potential score	domestication
	ISO	378.98	+	151.14	+
	VAL	350.89	-	-98.44	-
	BAL	571.66	++	306.85	++
	GEN	346.67	--	-359.55	--

"Domestication potential" and "Aquaculture potential" must be considered as synonyms. The co-use of the two names in this Ph-D thesis manuscript reflects the ongoing development of the index. We kept the name used in the submitted version for each article, but the names will be homogenized during the reviewing process as "Aquaculture potential"

Data was added from a fifth population[KIE], which is not included in the fourth chapter. These results still need to integrate behavioral traits (i.e. inter-individual distances and activity) for which phase II raw data still needs to be analyzed).

ACKNOWLEDGEMENTS

This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 652831 (AQUAEXCEL 2020 ). This output reflects only the author's view and the European Union cannot be held responsible for any use that may be made of the information contained therein. LT is supported by a grant from the French "Ministère de l'Enseignement Supérieur et de la Recherche". TV is supported by the Ministry of Education, Youth and Sports of the Czech Republic -projects CENAKVA (No. CZ.1.05/2.1.00/01.0024), CENAKVA II (No. LO1205 under the NPU I program), GAJU project (No. 060/2016/Z) and NAZV project (No. QJ 1510117). Authors acknowledge Laurent Espinat and Chloé Goulon (INRA, Thonon-Les-Bains, France) for their help with egg ribbon collection from Lake Geneva.

ACKNOWLEDGMENTS

Authors are grateful to Ivana Samková for her help with laboratory analyses and Camilla Nesbø for providing her dataset. They acknowledge all data providers: Daniel Żarski, Jacek

ACKNOWLEDGMENTS

We are grateful to the European Percid Fish Culture (EPFC, Belgium) group and all fish farmers which contributed to the survey led in this work. We gratefully acknowledge Yannick Ledoré (URAFPA, France), Fodor Ferenc (Balatoni Halgazdálkodási Nonprofit Zrt, Hungary), Katja Kulo and Pasi Ala-Opas (LUKE, Finland) for their help with sampling. Special thanks to Joëlle Couturier (URAFPA, France) and Carlos Alberto Espinal (Landing Aquaculture, the Netherlands). Authors acknowledge Fabrice Teletchea (URAFPA, France), Nicolas Poulet (AFB, France), Simon Dellicour (ULB, Belgium), and Edwige Quillet (INRA, France) for their helpful comments and discussions on this experimental design. LT was supported by a grant from the French Ministère de l'Enseignement Supérieur et de la Recherche.

ACKNOWLEDGMENTS

We gratefully acknowledge Yannick Ledoré (URAFPA, France), Zoltán Bokor, Árpád Ferincz, Adam Staszny (SZIU, Hungary), Fodor Ferenc (Balatoni Halgazdálkodási Nonprofit Zrt, Hungary), Sami Vesala, Katja Kulo, and Pasi Ala-Opas (LUKE, Finland), Espinat Laurent, and Goulon Chloé (INRA, France) for their help with sampling. Special thanks to Joëlle Couturier (URAFPA, France). Authors acknowledge Fabrice Teletchea (URAFPA, France), Nicolas Poulet (AFB, France), and Edwige Quillet (INRA, France) for their helpful comments and discussions on this experimental design. LT was supported by a grant from the French Ministère de l'Enseignement Supérieur et de la Recherche.

DATA AVAILABILITY

All data generated or analyzed during this study are included in this article (and its

DATA AVAILABILITY

All proxy-based matrices are available in Figshare (doi: 10.6084/m9.figshare.11407128 / https://figshare.com/s/1067e47637c5572caaf7). All haplotype sequences are available in Genbank (MN939382 to MN939395).

OBJECTIVES AND HYPOTHESES

The major aims of this PhD work were: A1-Demonstrating the usefulness of geographic differentiation for domestication of a targeted species.

A2-Conceptualizing and applying a standardized and pragmatic method aiming at integrating geographic differentiation in domestication processes.

We implemented this method on a species used as a test-case: the European perch (Actinopterygii, Perciforms, Percidae, Perca fluviatilis). We hypothesized that: H1: There is a geographic differentiation in Perca fluviatilis for key traits.

H2:

There are units with high potential for aquaculture within species.

In order to answer to the first aim A1, the chapter 1 is focused on demonstrating that Perca fluviatilis geographic differentiation can be useful for domestication and subsequent production (validation of H1).

The chapter 2 aimed at conceptualizing a method to integrate geographic differentiation in domestication processes in order to facilitate new species domestication and production (aim A2). This method consists of three steps: (i) classifying wild populations into prospective units (i.e. groups of differentiated conspecific and allopatric populations) which are likely divergent for key traits in aquaculture, (ii) evaluating the performance of the different prospective units in culture conditions, and (iii) identifying the prospective unit with the highest potential for aquaculture. The next two chapters aimed at applying the method on Perca fluviatilis first life-stages.

The first step is illustrated in chapter 3. This chapter aims at classifying wild populations in prospective units in order to restrict the number of populations to study in the step 2 (aim A2). As mentioned earlier, it is not feasible and pragmatic to compare all populations across a species distribution range. One way to limit the range of possibilities relies on the use of a classification method which would assemble populations that are likely undifferentiated and highlight population groups which are likely differentiated in key traits. One could expect that the use of already available classifications (e.g. subspecies, management units, evolutionarily

CONFLICT OF INTEREST AND ETHICAL STATEMENT

Conflict of Interest: The authors declare that they have no conflict of interest.

Ethical approval: "All applicable international, national, and/or institutional guidelines for the care and use of animals were followed by the authors." ABBREVIATIONS GEN: Lake Geneva VAL: Lake Valkea-Müstajärvi ISO: Lake Iso-Valkjärvi RAS: Recirculated Aquaculture System

SUPPORTING INFORMATION

DECLARATIONS

Ethics approval and consent to participate

Sample providers complied with institutional, national, and international guidelines and regulations as well as Nagoya protocol to obtain our fish clip samples. No ethic committee approval was necessary for the collection of fish clips. All fish treatments used for sampling were in accordance with the guidelines of the European Directive (2010/63/EU) on the protection of animals used for scientific purposes (and the French Animal Care Guidelines).

In addition, P. fluviatilis is neither an endangered species nor a species at risk of Extinction according to the IUCN (Red List category: Least Concern).

Competing interests

Declarations of interest: none

Funding

Author Contributions

LT, PF, and TL designed the study. LT, TV, JP, ZK, JK, PF, and TL contributed to the collection of fin samples. LT, TV, and MB contributed to laboratory analyses. LT, TV, SD, PF, FT, and TL analyzed and interpreted the results. All authors participated to manuscript writing. All authors read and approved the final manuscript.

Availability of data and materials

Mitochondrial sequences are available in GenBank (accession numbers: MG969725 to MG969793).

During the two phases, oxygen concentration (8.5 ± 2.3 mg.L -1 ) and temperature (20.0 ± 0.6°C) were checked daily in all tanks (± standard error). Ammonium and nitrite concentrations (means inferior to 0.05 mg.L -1 ) and pH (7.7 ± 0.6 mg.L -1 ) were monitored three times a week (± standard error). Tanks were cleaned daily after first feeding and dead individuals were removed every morning.

Larviculture performance assessment

A trait is considered in this study at the replicate level. Each trait value is obtained from the mean of individual values.

Survival and development traits

Survival rate is one of the key traits contributing to the success of larviculture production (Kestemont et al. 2015a;[START_REF] Conceicao | Success factors for larval fish production[END_REF]. Because of fast decomposition of dead larvae, it was not possible to count dead larvae during the first five days post-hatching.

Consequently, the daily count of dead larvae was only performed in phase II. Therefore, survival rate in phase I was calculated for each cylindro-conical tank thanks to the final count of larvae using the following formula: Nf*100/(Ni-Ns), where Nf is the final number of fish counted at the end of phase I, Ni the initial number of fish, and Ns the number of fish sampled along the phase (i.e. for behavior experiments, see below). For phase II, the Bergot survival rate [START_REF] Bergot | The effect of compound diets feeding on growth survival of coregonid larvae[END_REF]) was used since it takes into account the number of fish removed for sampling and the daily mortality. Two traits related to the development of individuals and essential for larviculture were considered (Kestemont et al. 2015a): swim bladder inflation rate and deformity rate. Swim bladder inflation rate was estimated at the end of each experimental phase (following the protocol used in Jacquemond 2004; 20 g.L -1 of sea salt and 70 mg.L -1 of MS-222): 100 * (SB+/Nf) with SB+ the number of larvae with swim bladder and Nf the final number of larvae. Deformity rate was estimated in the final counting of each experimental phase using the following formula: 100*(Nm/Nf) with Nm the number of deformed larvae (only visible column deformities) and Nf the final number of larvae counted.

Finally, the volume of the yolk sac was also evaluated at one day post-hatching since it reflects the quantity of nutritional reserves available before exogenous feeding (Kestemont et al. 2015a). It is calculated using the following formula: π/6 * YSL*YSH 2 , where YSL is the length of the yolk sac and YSH the height of the yolk sac [START_REF] Bagarinao | Yolk resorption, onset of feeding and survival potential of larvae of three tropical marine fish species reared in the hatchery[END_REF]).

Ibarra-Castro 2013). However, previous scoring methods integrate some traits for which intraspecific variability is unlikely (e.g. presence of bones in [START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF] or do not include all traits considered here in the multi-function and multi-trait approach. Therefore, we propose a domestication potential score that aims at making a synthesis at the multi-trait level.

The first step of this score calculation consists in ranking populations according to their performance for each trait (average rank per trait obtained from the mean of all replicate ranks; Appendix S2) when a statistical difference between populations was highlighted.

Then, since all traits do not present the same level of importance for production according to fish farmers (which was confirmed in a survey we led before this work; see Appendix S2), it is necessary to adjust the importance given to each trait through the use of weighting coefficients (between zero and 100; adapted from [START_REF] Quéméner | Selection method of new candidates for finfish aquaculture: The case of the French Atlantic, the Channel and the North Sea coasts[END_REF], similarly to breeding goals index but for which each trait is weighted according to its socio-economic value, [START_REF] Chavanne | A comprehensive survey on selective breeding programs and seed market in the European aquaculture fish industry[END_REF]. Thanks to the survey addressed to perch farmers, we were able to assign to each trait an average weighting coefficient (Appendix S2). For each trait, we then divided the average weighting coefficient attributed by fish farmers by the rank of the population (Appendix S2). When traits were evaluated over two phases, they were considered as two separate traits in the calculation of the domestication potential score. Once this ratio is attributed to each trait, the sum of all ratios allows calculating the domestication potential score for each population (Appendix S2). Overall, the domestication potential score (ranging from 0 to ∞) is defined as:

Where: n corresponds to the number of traits, i=1 the first trait evaluated, i the trait considered, n = the last trait considered, and the weighting coefficient corresponds to the weight attributed to each trait by perch farmers and the rank corresponds to the rank attributed to the population for each trait.

The population with the highest score is the population with the highest potential for domestication.

Compliance with ethical standards

All along this experiment, individuals were handled as little as possible. All procedures used in the experiment were in accordance with national and international guidelines for protection of animal welfare (Directive 2010/63/EU). This study was conducted with the approval Animal Care Committee of Lorraine (CELMA n°66) and the French Ministry of Higher Education, Research, and Innovation (APAFIS13368-2018020511226118, APAFIS17164-2018101812118180).

CONFLICT OF INTEREST

The author(s) declare no competing interests. Supplementary Information files).

AUTHOR CONTRIBUTION

PF, TL, AP, and LT conceived and designed the experiment. All authors performed the experiment and/or analyzed data. TL, PF, and LT wrote the manuscript and all authors contributed to the final version. working with perch larviculture were questioned. We asked them to give their opinion on the importance of different traits involved in larval stages (from "not important" to "very important"). A weight coefficient was attributed to each opinion category: 0 for "not important", 25 for "slightly important", 50 for "Important", 75 for "Fairly important", and 100 for "very important". The first step consists in calculating an average weight coefficient for each trait taking into account farmers' opinions (step A). Then, for each replicate, populations are ranked per trait when a significant statistical differentiation was highlighted (p-value<0.05;

Step B). This allows calculating an average rank per population and per trait (Step B). Finally, a score per trait and per population is calculated by dividing the average weighting coefficient by the average rank (Step C). The sum of all these scores allows calculating for each population a domestication potential score.

Appendix S3:

Correlation matrix between all traits (I relative to phase I and II referring to phase II) based on Pearson's correlation coefficients (between -1 and 1; except for comparisons with an asterisk (*) for which Spearman's correlation coefficients were used). Correlation values are indicated for each test and statistically significant correlations (p-value<0.05) are highlighted in bold. The color corresponds to the value of the correlation coefficient (red for positive coefficients, blue for negative coefficients).

ABSTRACT

Considering wild inter-populational phenotypic differentiation can facilitate domestication and subsequent production of new species. Indeed, populations can present phenotypic specificities which can be of interest for domestication. Starting new domestication processes with the best population(s) available in the wild would optimize chances of success in a breeding environment. However, comparing all populations across a species range to identify populations exhibiting trait expressions interesting for domestication (i.e. key traits) is not feasible. Therefore, proxies highlighting inter-populational divergences in key traits are needed. Here, we assessed the relevance of three alternative proxies of inter-populational divergences in key traits for aquaculture: (i) genetic distance, (ii) habitat divergence, and (iii) geographic/hydrologic distances. We performed this evaluation on seven allopatric populations of the European perch (Perca fluviatilis) for which divergences in key traits had been already shown. Our results revealed differences in the correlation degree between the alternative proxy-based and key trait-based distance matrices, with the genetic proxy being correlated to the highest number of key traits. However, no proxy was correlated to all interpopulational divergences in key traits. Consequently, we suggest using a multi-proxy assessment along with a prioritization of populations that should be further investigated to detect divergences for their key trait expressions.

Keywords

ADDITIONAL INFORMATION

Conflict of interest

The author(s) declare no competing interests. S1: Correlation results between proxy-based (geographic, hydrologic, genetic, and habitat proxies) and TIA-based distance matrices with r the Mantel correlation value and its associated p-value (significant r (p-value<0.05) are indicated in bold).

TIA

Mantel test (r) results alternative methods/improvements are discussed in this section. Applications of the three-step method for European perch larviculture are also discussed at the end of this section.

Geographic

1. Sampling for the phylogeographic structure assessment

The phylogeographic structure could only be studied in western Eurasia, in addition of one location from Siberia. Therefore, samples were missing from the Eastern range of distribution where some specificities could eventually be seen. A more extensive sampling could be performed in Eastern Eurasia but the collection and transportation of biological material in these regions is more challenging.

The sampling size in some regions was low (e.g. Scandinavia, south-east Europe; Russia), especially for estimating genetic diversity. Yet, this sampling size has already been used in previous phylogeographic studies (e.g. [START_REF] Fontanella | Phylogeography of Diadophis punctatus: Extensive lineage diversity and repeated patterns of historical demography in a trans-continental snake[END_REF][START_REF] Cook | Phylogeography of the mouth-brooding freshwater fish Glossamia aprion (Apogonidae) in northern and eastern Australia: Historical biogeography and allopatric speciation[END_REF]. Moreover, results are congruent in these regions with [START_REF] Nesbø | Genetic divergence and phylogeographic relationships among European perch (Perca fluviatilis) populations reflect glacial refugia and postglacial colonization[END_REF] and a sliding window approach was used to evaluate local genetic diversity, which allowed us to minimize the effect of small sampling sizes. Indeed, this approach does not use the arbitrary "population" delimitation since the genetic diversity is estimated within a circular sliding window and is corrected for unequal sampling size. Except for remote sampling sites, this approach allowed minimizing the effect of small sampling sizes.

Bioassay experimental biases and potential improvements 2.1 Stock constitution for bioassays

Variation among families within a population can be almost as high as variation between populations [START_REF] Gunnes | Selection experiments with salmon IV Growth of Atlantic Salmon during two years in the sea[END_REF]. In addition, intrapopulation genetic variability might contain sub-optimal adapted genotypes [START_REF] Carvalho | Evolutionary aspects of fish distribution: genetic variability and adaptation[END_REF]. Therefore, an optimal approach would rely on sampling broodstock and simultaneously rear separate family lines for each prospective unit. This would allow quantifying intra-population differentiation vs 1.4 Towards a single or a multi-proxy step 1?

Was the genetic proxy the right one?

The relevance of the genetic proxy was only checked on phase I (1 dph to 26 dph; fifth chapter). Therefore, to check the consistency of conclusions, I performed the same analysis (MRDM+CA and Mantel tests) using available data for phase II (27 dph to 60 dph) regarding seven key traits on five populations 2 (GEN, KIE, ISO, VAL, BAL). There is no interpopulational differentiation for specific growth rate (length and weight), final growth heterogeneity (length and weight), and aggressive interaction rate, which were therefore not included in this analysis. The MRDM-CA results (Table 14) point to a similar conclusion than the fifth chapter: no proxy-based distance matrix is correlated to all key trait distance matrices. However, it also shows that among alternative proxies, the genetic proxy is the most relevant since it is correlated to all key traits except for deformity rate.

Two alternative strategies possible

Given that the genetic proxy is not correlated to all key traits, two alternative approaches were suggested in the fifth chapter.

The first one consists of selecting the proxy which is correlated with the most important keytraits according to fish farmers/stakeholders. Using the survey from the fourth chapter, we can see that this strategy is limited in our case since the two most important traits are correlated to two different proxies (Table 15). For instance, only considering the habitat distance proxy would lead to an under-estimation of differentiation in key traits. However, a pragmatic alternative would be to use only the genetic proxy, as performed in this work. Indeed, when considering both phases and ignoring the collinearity between proxies (i.e. focusing on Mantel test results), the genetic proxy is correlated with 12 trait-based distance matrices out of 15 and with correlation values overall higher than other proxies (higher than the hydrologic proxy correlated to 13 trait-based distance matrices). Moreover, when performing a multivariate statistical analysis to check the overall differentiation between prospective units considering all traits simultaneously, there is a differentiation between all prospective units for phase I (perMANOVA: DF=2, F=19. 28, p-value<0.001) and between the European Plain vs Danube-Eastern Europe for phase II (perMANOVA: DF=2, F=17.62, p-value<0.001).

Therefore, the use of the genetic proxy is useful for highlighting major differences between prospective units. The usefulness of using neutral genetic differentiation to highlight divergences in key traits was previously demonstrated in P. fluviatilis (Vanina et al. 2019a) and P. flavescens [START_REF] Rosauer | Development of yellow perch (Perca flavescens) broodstocks: Initial characterization of growth and quality traits following grow-out of different stocks[END_REF]. All traits do not drive to the same conclusions regarding the biological unit with the highest potential for aquaculture as highlighted in the fourth chapter. This implies that there is no "ideal" prospective unit/population presenting all best performances for all traits (as suggested previously when comparing allopatric populations for European sea bass; [START_REF] Vandeputte | Multi-site evaluation of the rearing performances of 5 wild populations of European sea bass (Dicentrarchus labrax)[END_REF]. Therefore, the use of an aquaculture potential index was proposed in the fourth chapter to simplify the interpretation of conclusions. Such index implies to attribute a weighting coefficient to each trait and to rank populations. However, ranking populations can be problematic when considering statistical differentiations. Indeed, in a simple case with three populations A, B, and C for a given trait: A has a significantly higher expression than B, C is not statistically different from A and B, with higher values considered as beneficial for domestication. In this example: A is ranked first, B ranked second, but no rank can be attributed to C. An average rank is not optimal for C since it is not different neither from A nor B. Therefore, an aquaculture potential index was proposed in which a mean rank (average of the ranks from the three replicates) is attributed to each biological unit based on the raw values of key trait expressions (Figure 14A). However, there is a risk that the aquaculture potential index score may not well appreciate the true differences between populations. For instance, different biological units may have very close phenotypic performances for the highest weighting traits but very different for the lowest weighting traits. With the ranking approach, units with the highest ranks for the most important traits will be favored although their performance values on these main traits may not be very different from the other units while the main differences may be observed on the secondary traits.

An alternative index could be used and consists of using directly trait values rather than ranks to take into account deltas of differences between populations. Since value ranges are different among traits, this approach requires standardizing data (centering and scaling: mean of zero and standard deviation of one). The new formula considering phenotypic standardized values is inspired from the selective index using in quantitative genetics [START_REF] Moreira | Selection index based on phenotypic and genotypic values predicted by REML/BLUP in papaya[END_REF];

Figure 14B

). Attention should be paid to the trait expression expected. For instance, while for most traits the highest value is the most interesting (e.g. growth rate, survival rate), for some other traits the lowest values are of higher interest (e.g. activity, inter-individual distances, deformity rate). Therefore, for these traits, for which the lowest values are of interest, the standardized values should be multiplied by "-1". In formula B, just like formula A, the higher the score is, the more interesting the biological unit is for domestication. Testing formula B on data used for the fourth chapter, the same conclusions are reached but the

LIST OF PUBLICATIONS

Unlocking the wild potential: integration of geographic differentiation in domestication processes to facilitate fish aquaculture diversification

Nowadays, there is a will to develop a more sustainable aquaculture. One of the ways supported to promote the sustainability of the aquaculture sector relies on the production diversification, notably through the domestication and production of new species. However, domestication is a long and difficult process which can fail due to technical challenges, socio-economic limitations, or inadequate biological features of the species of interest. Yet, some of these biological features can also vary at the intraspecific level, between allopatric populations. Indeed, geographic differentiation can shape genetic, phenotypic, and ecologic specificities, which could lead to unique domestication predisposition or socio-economic attractiveness among allopatric populations. Therefore, choosing wild populations exhibiting a high potential for aquaculture (i.e. presenting interesting expression of key traits) could facilitate the domestication and production of new species. This PhD work was aimed at (i) assessing if geographic differentiation could be useful in domestication/production of a targeted species and (ii) developing and applying an integrative method to integrate geographic differentiation in domestication programs. The approach developed was tested on a species of interest for inland aquaculture diversification, the European perch (Perca fluviatilis), and targeted first life stages. The method consists of three steps: (i) classifying wild populations into prospective units (i.e. groups of populations differentiated) which are likely divergent for key traits in aquaculture, (ii) evaluating the performance of the different prospective units in standardized culture conditions through a multi-function and multi-trait approach, and (iii) identifying the prospective unit with the highest potential for aquaculture. The first step allowed identifying five prospective units: the European Plain, Danube, Northern and Eastern Fennoscandia, Eastern Europe, and the Balkans units.

The second step highlighted a geographic differentiation in key traits for aquaculture in P. fluviatilis. The third step allowed identifying differential potentials for aquaculture between prospective units. Despite some limitations, this three-step approach could allow facilitating domestication of new species or species at incipient stages of domestication which face major bottlenecks in domestication and/or production.

Keywords: Intraspecific, Domestication, Aquaculture, Potential, Multi-trait, Sustainability

Déverrouiller le potentiel sauvage: Intégration de la différenciation géographique dans les processus de domestication pour faciliter la diversification piscicole

De nos jours, il existe une volonté de développer une aquaculture plus durable. L'une des voies prometteuses pour promouvoir la durabilité du secteur de l'aquaculture repose sur la diversification de la production, notamment par la domestication et la production de nouvelles espèces. Cependant, la domestication est un processus long et difficile qui peut échouer en raison de défis techniques, de limitations socio-économiques ou de caractéristiques biologiques inadaptées des espèces. Toutefois, certaines de ces caractéristiques biologiques peuvent varier au niveau intraspécifique, entre populations allopatriques. En effet, la différenciation géographique peut façonner des spécificités génétiques, phénotypiques et écologiques qui pourraient entraîner des différences de prédisposition à la domestication ou d'attraits socio-économiques entre populations allopatriques. Par conséquent, le choix de populations sauvages présentant un potentiel élevé pour l'aquaculture (c'est-à-dire présentant une expression intéressante de traits clés) pourrait faciliter la domestication et la production de nouvelles espèces. Ce travail de thèse visait à (i) évaluer si la différenciation géographique pouvait être utile dans la domestication et production d'une espèce cible et (ii) développer et mettre à l'épreuve une méthode intégrative pour considérer la différenciation géographique dans les programmes de domestication. L'approche développée a été testée sur une espèce d'intérêt pour la diversification de l'aquaculture continentale, la perche européenne (Perca fluviatilis), et a ciblé les premiers stades de vie (nurserie). La méthode comprend trois étapes: (i) la classification des populations sauvages en unités prospectives (c'est-à-dire en groupes de populations différenciées) qui sont susceptibles de présenter des divergences pour des traits clés, (ii) l'évaluation des performances des différentes unités prospectives dans des conditions d'élevage standardisées par une approche multi-fonction et multi-trait, et (iii) l'identification de l'unité prospective ayant le plus fort potentiel pour l'aquaculture. La première étape a permis d'identifier cinq unités prospectives: Plaine européenne, Danube, nord et est de la Fennoscandie, Europe de l'est et Balkans. La deuxième étape a mis en évidence une différenciation géographique pour des traits clés pour l'aquaculture de P. fluviatilis. La troisième étape a permis de mettre en évidence des différences de potentiel aquacole entre des unités prospectives. Malgré certaines limites, cette approche en trois étapes pourrait permettre de faciliter la domestication de nouvelles espèces ou d'espèces au début du processus de domestication qui sont confrontées à d'importants goulots d'étranglement en matière de domestication et/ou de production.

Mots clés : Intraspécifique, Domestication, Aquaculture, Potentiel, Multi-trait, Durabilité