Sinan Boztepe
email: sboztepe@mines-albi.fr

Rémi Gilblas
email: rgilblas@mines-albi.frc

Olivier De Almeida
email: olivier.dealmeida@mines-albi.frd

Yannick Le Maoult
email: lemaoult@mines-albi.fre

Fabrice Schmidt
email: fabrice.schmidt@mines-albi.fr

Cost-Effective Computational Method for Radiation Heat Transfer in Semi-Crystalline Polymers

This paper introduces a cost-effective numerical model for infrared (IR) heating of semi-crystalline polymers. For the numerical and experimental studies presented here semi-crystalline polyethylene (PE) was used. The optical properties of PE were experimentally analyzed under varying temperature and the obtained results were used as input in the numerical studies. The model was built based on optically homogeneous medium assumption whereas the strong variation in the thermo-optical properties of semi-crystalline PE under heating was taken into account. Thus, the change in the amount radiative energy absorbed by the PE medium was introduced in the model induced by its temperaturedependent thermo-optical properties. The computational study was carried out considering an iterative closed-loop computation, where the absorbed radiation was computed using an in-house developed radiation heat transfer algorithm -RAYHEAT-and the computed results was transferred into the commercial software -COMSOL Multiphysics-for solving transient heat transfer problem to predict temperature field. The predicted temperature field was used to iterate the thermo-optical properties of PE that varies under heating. In order to analyze the accuracy of the numerical model experimental analyses were carried out performing IR-thermographic measurements during the heating of the PE plate. The applicability of the model in terms of computational cost, number of numerical input and accuracy was highlighted.

INTRODUCTION

In terms of modeling the radiation heat transfer in optically heterogeneous media, numerous examples of modelling approaches exist in literature that adopt well-known optical scattering theories, such as Rayleigh-Debye-Gans [1] or Mie [2,[START_REF] Ber | i a r o n i[END_REF] theory which allows to predict the spatial distribution of the scattered light intensity accurately. However, such radiation heat transfer models that handle complex radiation physics may be computationally costly, especially if spectral or geometrical complexity in a heated component is involved [START_REF] Humphrey | Int. Conf. High Perf. Comput[END_REF]. In contrast to laser heating applications, the radiation emitted by an IR source and transferred through a polymer medium is not monochromatic, but in a range, which introduces such a complexity in terms of modeling of optical scattering, as the scattering behavior may change under varying wavelength in the spectral range of emitted radiation. Such a wavelength-dependent scattering behavior in semi-crystalline polymers was discussed in [START_REF] Boztepe | [END_REF]6].

Apart from the computational cost due to spectral complexity of IR radiation, the strong coupling between the microcrystalline structure of unfilled semi-crystalline thermoplastics and their optical scattering behavior may also increase the complexity of a numerical approach, and thus computational cost. It is known that optical scattering in semi-crystalline polymers are strongly related to their microcrystalline structure where the optical scattering behavior may evolve under heating, due to a potential change in their microcrystalline phase at the temperatures close to their melting ranges. It may therefore be useful to adopt a numerical model that considers this temperaturedependent optical behavior. Potente et al [7] proposed temperature-dependent optical properties for semi-crystalline polypropylene (PP), named as "effective absorption constant". However the temperature dependency in absorption characteristics of PP was modeled based on the change in the density of the polymer in the corresponding temperature range, so that it lacks the physical background due to no experimental characterization on its optical properties was performed. Similarly, temperature-dependent absorption properties were introduced as a numerical input for laser transmission welding (LTW) process simulations of short glass fiber filled and unfilled PP and PA6 in [8] whereas the behavior about the absorption characteristics under varying temperature was not highlighted.

In this paper, a cost-effective numerical approach was proposed for unfilled semi-crystalline thermoplastics considering the temperature-dependent behavior in their optical characteristics. For the study, temperaturedependent directional-hemispherical transmittance (T λ i, (T)) and reflectance (R λ i, (T)) of semi-crystalline PE was experimentally analyzed considering different temperatures between 25 o C and 128 o C. Assuming an optically homogeneous medium, the measured T λ i, (T) and R λ i, (T) were used to calculate the temperature-dependent extinction coefficient (β λ (T)), which considers an evolution in the optical characteristics of PE under heating condition. The calculated β λ (T) were then used as numerical input so that the temperature-dependency of absorbed radiative energy by the PE medium was taken into account in the model. The computational study was carried out considering an iterative closed-loop computation, using an in-house developed radiation heat transfer algorithm -RAYHEAT-and the commercial software -COMSOL Multiphysics-where the closed-loop iterations was established using MATLAB LiveLink. In order to analyze the accuracy of the numerical model experimental analyses were carried out performing IR-thermographic measurements for the case of IR-heating of the PE plate. The model developed here proposes a numerical approach to consider the optical scattering and its effect under heating condition indirectly that is governed by microcrystalline morphology. In other words, the effect of optical scattering on the optical characteristics of semi-crystalline PE was taken into account without modeling the spatial distribution of the scattered light intensity which offers computationally cost-effective numerical solutions.

TEMPERATURE DEPENDENCY IN THE THERMO-OPTICAL PROPERTIES OF SEMI-CRYSTALLINE POLYMERS

The T λ i, (T) and R λ i, (T) tests were done over the spectrums of 0.25-2.5μm and 2-25μm using PE samples in three different thicknesses. All the samples were quenched into liquid nitrogen (LN 2 ). The details of the sample preparation is presented in [START_REF] Boztepe | [END_REF]. T λ i, (T) and R λ i, (T) of each PE sample were measured at various temperature steps, between 25 o C and 128 o C. The T λ i, (T) tests were performed employing FT-IR spectrometer (Perkin Elmer 950) combined with an integrating sphere. For the tests, a heating stage (Bruker A599) was positioned at the entrance port of the integrating sphere, so that the samples were mounted into the heating stage and their T λ i, (T) were measured. For the measurement at each step, the samples were heated up and waited for 2 minutes in order to reach a steady-state temperature. In total, T λ i, (T) of each PE sample was measured at 14 different temperature points. Similarly, for each PE sample, R λ i, (T) measurements were performed at 10 different temperature steps. The R λ i, (T) tests were done employing SOC-100 model Hemispherical Directional Reflectometer (HDR) built by Surface Optics Corporation. For these tests, the samples were heated using the heating unit of the SOC-100 HDR. Details of the PE samples and the temperature steps of the tests are presented in Table 1. It should be noted that the temperature steps mentioned in Table 1 represent the actual temperature on the sample surface where the measurements were obtained. In other words, it was observed that the set temperature on the heating devices that were used in T λ i, (T) and R λ i, (T) tests and the actual temperature on the measurement zone are different. Therefore, preliminary tests were done in order to determine the actual temperature on the measurement zone. The actual temperatures adopted in the R λ i, (T) tests were determined using identically thick dummy PE samples on the heating unit of SOC-100 HDR. In addition, the details of the preliminary tests for the transmittance measurements is revealed in [START_REF] Boz T E Pe | SFT 2017-Congrès Annu[END_REF] . In Fig. 1(a) and (b), the typical trend obtained in each T λ i, (T) and R λ i, (T) tests were presented respectively. It is seen in Fig. 1(a) that the T λ i, of the 0.75 mm thick sample increases under heating where the increase is more pronounced after 116 o C, that reflects the temperatures close to the melting range of the polymer [START_REF] Boztepe | [END_REF]. It should also be mentioned that no significant change was observed in T λ i, for the wavelengths greater than 1.7 μm, where also a significant noise was detected during the measurements at high temperatures. It was thus assumed that T λ i, remains unchanged under heating considering the spectrum between 1.7 and 2.5 μm. In contrast to the trend in T λ i, (T), there is an inverse relation between the R λ i, of PE and temperature. As shown in Fig. 1(b), the temperature change is less effective on the reflectance properties of PE in comparison to its temperature-dependent transmittance. For the sake of clarity in the trends observed at both the T λ i, (T) and R λ i, (T), certain number of data are presented in Fig. 1 As our previous studies [START_REF] Boztepe | [END_REF][START_REF] Boztepe | 19 th Int. ESAFORM Conf. on Mater. Form[END_REF] showed that the strong coupling between microcrystalline morphology and the transmittance characteristics of PE becomes negligible in MIR range (2-25μm), no temperature dependency was assumed for transmittance characteristics of PE in MIR range. Hence, T λ i, of the identical PE samples measured at room temperature was adopted for this range. Conversely, no temperature-dependent measurements were able to be obtained for the reflectance measurement considering the wavelengths lower than 2 μm, due to the limitations in the testing devices employed and the spectral responses of their detectors. It was therefore assumed that reflectance characteristics of PE are independent of temperature. Although this is not a rigorous assumption, further analyses on the PE samples prepared with different microcrystalline structure were tested at room temperature and a slight effect of the microcrystalline morphology on the reflectance was observed. It may therefore be stated that the reflectance behavior of PE may not change dramatically in case that a change in its microcrystalline structure under varying temperature is seen. Based on the measured T λ i, (T), R λ i, (T) and the adopted assumptions, β λ (T) of PE was calculated considering an optically homogeneous medium. Using the transmittance and the reflectance characteristics of an optically homogeneous medium, it may be possible to define the β λ [START_REF] Howell | Thermal Radiation Heat Transfer[END_REF]. Hence, β λ may be calculated for each adopted temperature step that eventually leads to:

A λ i, (T)+ T λ i, (T)+ R λ i, (T)= 1 with; (1) 2 2 ) ( 1 ) 1 (
) ( i, T T and 2 2 2 2 ) ( 1 ) 1 ( 1 ) ( i, T R (2)
The computation of β λ at each temperature step was carried out in MATLAB, adopting an inverse method based on SQP (Sequential Quadratic Programming) estimation algorithm, so that the equation 2 was solved for computing ρ λ and τ λ values, and eventually β λ . The background of this in-house developed estimation algorithm is explained further in [START_REF] Asséko | [END_REF]. In Fig. 2, the computed β λ (T) values are presented considering the spectrum between 0.6-7μm. Again, for the sake of clarity, some of the computed values are not presented in the figure. Furthermore, the drop in β λ under heating is illustrated further in the figure at right, including the spectrum between 0.6-1.6 μm. This may be plausible, as the change in the T λ i, (T) values is significant in this spectrum. Apart from this, it is clear that the trend in β λ (T) is monotonically decreasing under heating, except the computed β λ at 128 o C. This is due to the fact that a slight drop in T λ i, were observed for all the PE samples after the measurement at 126 o C, which resulted to have slightly higher β λ computed at 128 o C, in comparison to the computed one at 126 o C. This behavior was also observed in our previous study [START_REF] Boz T E Pe | SFT 2017-Congrès Annu[END_REF], which can be attributed to disintegration of polymer at semi-molten state, and therefore potential thickening in the measurement zone of the vertically positioned sample. Because of this limitation in T λ i, (T) tests, the calculated extinction coefficient at 128 o C is ignored in this study. Hence the β λ (T) computed at 13 temperature steps were used as input in the numerical model.

RADIATION HEAT TRANSFER MODELING APPROACH WITH TEMPERATURE-DEPENDENT OPTICAL PROPERTIES AND EXPERIMENTAL COMPARISONS

Background of the numerical model

As aforementioned, the computational study was carried out considering an iterative closed-loop computation, where the absorbed radiation was computed using in-house developed algorithm, RAYHEAT, and transferred into COMSOL. The current version of RAYHEAT is based on optically homogeneous medium assumption, hence, attenuation of radiative energy is computed adopting Beer-Lambert Law, as shown in Equation 3 [START_REF] Howell | Thermal Radiation Heat Transfer[END_REF]. The further details about RAYHEAT, including ray tracing method, and discretization of emitted rays can be found in [13].

) ( )) ( ) ( ( ) ( ) ( z I z D z z I z dz dI ( 3
)
The absorbed energy, namely radiative source term ( q r ), at the depth "z" of a heated medium can be defined in Equation 4, at which β λ is the sum of both absorption (κ λ ) and scattering coefficients (D λ ): In order to take into account β λ (T) as a numerical input in the model, a close-loop iterative approach was developed. The working algorithm of the model is displayed schematically in Fig. 3. As RAYHEAT is a MATLABbased code, the iterative closed-loop between RAYHEAT and COMSOL was established using MATLAB LiveLink feature which allows to transfer the computed q r into COMSOL as a numerical input, solves the transient heat transfer problem to predict the temperature field and calls back RAYHEAT for updating the q r of polymer medium regarding the computed temperature at the end of the corresponding iteration step. By this way, the transient heat transfer equation solved for the IR-heating of PE is formulized as:

p r C k q xyz t (5)
Therefore, the change in the amount of radiative energy absorbed by the PE medium -which is a function of the temperature and the spatial coordinates of the modeled mesh element-, is introduced in the model. The computation time for q r was discussed in [13] in terms of number of rays, mesh element and geometrical calculation of modeled rays. In order to reduce the computation cost, the radiative energy that may be absorbed by each modeled 3D mesh element was computed considering the calculated β λ (T) at 13 different temperature steps and saved before starting the iterative closed-loop temperature field computations. In the model, if a computed temperature in a mesh element is between these 13 steps, the numerical model q r interpolates regarding the q r of the 2 most close temperature steps. Otherwise the model adopts the q r of 126 °C, for the mesh element temperatures higher than 126°C.

Experimental -numerical comparisons for IR-heating of PE plate

The accuracy of the developed model was analyzed performing an IR-heating test using a rectangular PE plate with dimensions of 78x78x2.2 mm. The plate was heated with a single IR-lamp (1kW) at which 100% of its total power input was utilized. The front surface of the PE plate was positioned 8cm away from the IR-lamp. In Fig. 4, the test setup for IR-heating of PE plate is presented at left. As it is seen on that figure, a plate-like barrier is positioned in front the IR-lamp where a small frame (70x70mm) is designed for positioning the PE plate. In addition, the front surface of the barrier is covered with metallic adhesive tape in order to avoid heating on the barrier, otherwise conduction heat transfer between the barrier and the PE plate may cause an erroneous temperature measurement. The reason for using a barrier is to perform an IR-thermographic measurement on the back surface of the PE plate, as some of the emitted radiation from IR-lamp may directly reach to the IR-camera and cause noise. For the surface temperature measurements, two thermocouples (TC) were also positioned on the back surface of the plate for comparing their recordings with the IR-thermography. The TC recordings and the IR-heating of the plate were started simultaneously and, it was observed that the temperature on the back surface became steady-state after 600 seconds where also an IR-thermography was taken. Due to the limitations in the IR-thermography of PE that are stressed in [START_REF] Boztepe | 20 th Int. ESAFORM Conf. on Mater. Form[END_REF], the measurement was obtained when the temperature of the plate was at steady-state.

The boundary conditions of the numerical model were built adopting the identical conditions as applied in the experimental test setup. In the model, the plate geometry was meshed with 4232 linear hexagonal elements, and the temperature of each mesh element was calculated as the average temperature of its nodes' temperatures. In the current study, the barrier around the PE plate was not modeled. Based on the findings from the experimental study, heating of the plate up to 600 seconds was simulated using 1500000 rays. The computation of the simulation took around 10 and 55 minutes for the computations of geometrical optics, and the q r (T), respectively. In Fig. 5, IRthermography of the plate scaled in radiometric values (UI) (a) and, the comparisons between the temperature profiles obtained from the experimental measurements and the numerical studies (b) are presented. The UI values obtained in the IR-thermography was converted into temperature using the methodology in [START_REF] Boztepe | 20 th Int. ESAFORM Conf. on Mater. Form[END_REF]. As displayed in Fig. 5(b), the predicted surface temperature is close (around 3 °C difference) in the middle zone of the plate regarding the numerically and experimentally defined vertical and horizontal profiles. Conversely, the difference between both the analyses becomes significantly great considering the zones close to the edge of the plate for both the horizontal and vertical profiles. This may be attributed to ignorance of heat losses due to conduction between the barrier and PE plate as the barrier around the plate was not modeled. In addition, the convergence studies for the number of modeled rays were not performed at this step which may change the final temperature field predictions.

CONCLUSIONS

The model presented in this study proposes a numerical approach to consider the optical scattering and the change in its behavior under heating condition indirectly, without modeling how the light scatters inside of polymer medium. In other words, the effect of optical scattering on the optical characteristics of semi-crystalline PE was taken into account without modeling the spatial distribution of the scattered light intensity which offers computationally cost-effective numerical solutions. The change in the directional-hemispherical optical characteristics of PE under heating conditions were experimentally analyzed and, it was demonstrated especially in the temperature ranges close to the melting range of PE and eventually used as numerical input. In this study, the experimental and numerical analyses showed that the model predicts the temperature closely in the middle zone of the PE plate, whereas there is a remarkable difference at regions close to the edge of the plate considering both the computed and measured surface temperature profiles defined on the normal and alongside to the IR-lamp. This may be attributed to ignorance of potential heat losses due to conduction between the barrier and PE plate as the barrier around the plate was not modeled in this study. In addition, the convergence studies for the number of modeled rays were not performed at this step which may cause to change the final temperature field predictions.

FIGURE 1 .

 1 FIGURE 1. Typical trend obtained in T λ i, R λ i, measurements of PE polymer under varying temperature

FIGURE 2 .

 2 FIGURE 2. β λ (T) of PE polymer between room temperature and 128 o C

FIGURE 3 .

 3 FIGURE 3. Working algorithm of the developed numerical model

FIGURE 4 .

 4 FIGURE 4. Test setup for IR-heating of PE plate (left) and the positions of mounted thermocouples on the back surface (right)

FIGURE 5 .

 5 FIGURE 5. IR-thermography taken at steady-state temperature (a) and the back surface temperature of PE plate obtained via numerical and experimental analyses (b)

TABLE 1 .

 1 The PE samples and the testing characteristics of the T λ

i, (T) and R λ i, (T) tests

Type of measurement Sample thickness (mm) Temperature steps for measurements ( o C)

	T λ	i, ( T)	0.25, 0.50 and 0.75	25, 48, 71, 84, 97, 110, 114, 116, 118, 120, 121, 122, 123, 126, 128
	R λ	i, (T)	0.25, 0.50 and 0.75	25, 71, 97, 103, 110, 114, 118, 120, 124, 128


Eric Clua

Benoit Beliaeff

Claude Chauvet

Gilbert David

Jocelyne Ferraris

Mekhi Kronen

Michel Kulbicki

Pierre Labrosse

Yves Letourneur

Dominique Pelletier

Olivier Thébaud

Marc Léopold

Towards multidisciplinary indicator dashboards for coral reef fisheries management

Keywords: Coral Reefs, Fishing, Co-Management, Indicators, Dashboard

The diversity of reef ecosystems, the multiplicity of reef resource uses and the breadth of the range of the island socio-cultural contexts concerned make coral reef fisheries (CRF) management in the South Pacific a complex task. The health and state of the targeted resources depend both on ecosystem characteristics (as determined by ecological and biological factors) and on fishing pressure, whose effects are only partly known. Increasing harvests from commercial and recreational fishing increasingly overlap with traditional subsistence activity, creating an important CRF management challenge. This paper presents a new approach to CRF assessment and monitoring by providing a set of multidisciplinary indicators. The fisheries system is assessed from three different viewpoints: ecology of targeted populations, exploitation and the broader socio-economic fishery context. The use of complementary indicators chosen from each of these fields could balance the chronic lack of human and financial resources for the management of these fisheries. We suggest the use of these indicators through an assessment grid or an indicator dashboard specifically adapted to given situations and management objectives determined through a participatory approach. The operational efficiency of this dashboard depends on i) dialogue between users, ii) the objectivity of the proposed monitoring, iii) the visual transcription of divergent/convergent interests amongst stakeholders, and iv) stakeholder involvement in the decisionmaking process. The use and constraints of such a tool are described with reference to Ouvea atoll (New-Caledonia, South Pacific) for which an analysis of available indicators for assessing fisheries status is presented.

Introduction

The status of coastal marine resources, such as fishes or invertebrates associated with coral reef ecosystems, is determined by a complex set of interactions between biological, ecological, environmental and anthropogenic factors. Fisheries have an impact on the intricate relationships between the thousands of species forming the communities associated with the wide range of coral reef habitats. As with many fisheries around the world, it is difficult to assess the consequences of fishing separately from other variations due to the inherent dynamics of marine ecosystems, climate variation and change and/or other human disturbances [START_REF] Pitcher | New perspectives in biogeography of coral reef fish in the Pacific using phylogeography and population genetics approaches[END_REF].

Multidisciplinary approaches have been proposed, taking into consideration resource and user relationships, in order to more efficiently assist fisheries management [START_REF] Mcmanus | Social and economic aspects of reef fisheries and their management[END_REF][START_REF] Botsford | The management of fisheries and marine ecosystems[END_REF][START_REF] Ridler | Rural development in the context of conflictual resource usage[END_REF]). The "Fishery System" concept of the early 1980s [START_REF] Corlay | La notion d'espace de production halieutique[END_REF][START_REF] Chaboud | L'approche système dans les pêches[END_REF] led to the "Ecosystem Approach to Fisheries", which includes ecosystem health (habitats and species) and societal needs and expectations in management [START_REF] Fao | Indicators for sustainable development of marine capture fisheries[END_REF].

All of these approaches are very data-demanding both for overall understanding of the system and for decision-making. However, the spatial heterogeneity and complexity of coral reef ecosystems, the scattered locations of fishers and the prevalence of informal relationships in trading networks complicate the gathering of information and consequently the management of coral reef fisheries (CRF). In the context of low public financial support for data collection and analysis and increasing population and fishing pressure, many island countries are particularly interested in low-cost and easy-to-use methods for fisheries assessment [START_REF] Green | Coral reefs in the Pacific: status and monitoring resources management[END_REF].

Thus, the arranging of data into indicators that help to better understand the present status and dynamics of fisheries has become a major challenge [START_REF] Fao | Indicators for sustainable development of marine capture fisheries[END_REF], particularly for reef fisheries. Indicators that facilitate fisheries management by reconciling logistical constraints, information quality and accuracy of results are needed. Such indicators have already been proposed for pelagic and temperate coastal fisheries, and reviews of indicators for finfishery management already exist (e.g. [START_REF] Trenkel | Performance of indicators derived from abundance estimates for detecting the impact of fishing on a fish community[END_REF]. However, few indicators have been specifically developed for CRF despite the increasing need for improved management of these tropical coastal fisheries.

In this paper, we focus on the interactions between coral reef resources, their ecology and direct and indirect anthropogenic impacts. We define resources as edible fishes that can be harvested from the reef ecosystem for trade, barter, gift or subsistence purposes. Although invertebrates can be an important resource, this paper covers only finfish as the other reef resources and their uses are not widely known. Our objective is to propose 1) a set of indicators to assess the status and dynamics of CRF and 2) an indicator dashboard to improve the information available for consideration in participatory management.

An understanding of natural and human factors that interact with fisheries and their relationships is necessary for the development and use of specific indicators. Thus the first part of the paper describes the main characteristics of CRF systems by considering three components: ecology, resource/exploitation and socio-economics. Subsequently, we review the variables used to characterize the status and dynamics of CRF and discuss the criteria to select them as possible indicators related to specific objectives. The last section explores the complementarities of these indicators and therefore the relevance of an approach based on several disciplinary points of view. This systemic method is achieved through an indicator dashboard that involves local stakeholders such as fishers in decision-making processes. Research programmes were undertaken on Ouvea Atoll reef fishery (New Caledonia, South Pacific), which is used as a case study for this approach. However, many similarities can be found with CRF in the Caribbean or in other areas in the Indo-Pacific.

Useful variables for potential indicators in coral reef fisheries

CRF status is affected by two general constraints: fishing pressure and ecosystem dynamics. A conceptual framework describing the CRF system is proposed, encompassing three main fields: ecology, exploitation and socio-economics (Fig. 1): i) ecology takes into account natural environmental effects and intrinsic fundamental processes (e.g. biology, predator-prey relationships); ii) exploitation is at the interface between the natural and the societal components of the system and focuses on the fishing activities and their impact on resources; and iii) socio-economics includes direct or indirect anthropogenic effects which influence fishing pressure Based on existing literature, useful variables for CRF management are therefore presented with respect to ecology, exploitation and socio-economics (Table 1); the advantages and weaknesses of some of them as potential indicators are then discussed.

Ecology of exploited coral reef fish

Spatial and temporal dynamics of reef fish communities

Coral reefs are characterised by very high fish diversity and species often showing wide geographical distribution, resulting in low endemism [START_REF] Mora | Patterns and processes in reef fish diversity[END_REF] and high similarity in species composition from one region to another [START_REF] Kulbicki | Checklist and biogeography of lagoon and reef fishes from New Caledonia[END_REF]. At a regional scale, the most important factors explaining the geographical variations of species diversity are the distance from the Centre of Biodiversity located in the Philippines-Indonesia-China Sea area (Planes and Galzin 1997), and island size and latitude [START_REF] Bellwood | Regional-scale assembly rules and biodiversity of coral reefs[END_REF]. Fish diversity is also affected by local factors (e.g. [START_REF] Letourneur | Comparaison des peuplements de poissons marins de trois îles de l'Indo-Pacifique (La Réunion[END_REF][START_REF] Gust | Spatial variability in reef fish distribution, abundance, size and biomass: a multi-scale analysis[END_REF]) such as reef type, seascape, biogenic habitat (corals, algae), depth, tide and current, terrigenous flows and human activities. Local environmental and anthropogenic factors influence the very heterogeneous habitats concerned at a small to medium spatial scale, leading to a high level of variation in the composition and structure of fish assemblages at these scales (e.g. [START_REF] Galzin | Structure of fish communities of French Polynesia coral reefs -spatial scales[END_REF][START_REF] Harmelin-Vivien | Reef fish community structure: an Indo-Pacific comparison[END_REF][START_REF] Kulbicki | Bilan de 10 ans de recherche (1985-1995) par l'ORSTOM sur la structure des communautés des poissons lagonaires et récifaux en Nouvelle-Calédonie[END_REF].

Medium-and short-term (less than three years) variability of fish communities is usually much lower than spatial variability (Letourneur 1996a,b); longer-term variations are not well documented [START_REF] Galzin | Objectives and background to the 1994 Franco-Australian expedition to Taiaro Atoll (Tuamotu Archipelago, French Polynesia)[END_REF][START_REF] Chittaro | Structure of patch-reef fish assemblages at St. Croix, US Virgin Islands, and One Tree Reef, Australia[END_REF]. Indeed, the present level of knowledge on the dynamics of harvested fish assemblages is limited, as most studies focus on the biology or ecology of small sedentary species. Biologists generally work at smaller scales than fishery scientists [START_REF] Polunin | Greater biomass and value of target coral-reef fishes in two small Caribbean marine reserves[END_REF] and few ecological studies have considered the abundance of target species (e.g. [START_REF] Jennings | The effects of fishing on the diversity, biomass and trophic structure of Seychelles reef fish communities[END_REF][START_REF] Russ | Natural fishing experiments in marine reserves 1983-1993: community and trophic responses[END_REF][START_REF] Letourneur | Distribution spatiale des stocks de poissons récifaux démersaux d'intérêt commercial et effort de pêche en Province Nord de Nouvelle-Calédonie (Pacifique occidental)[END_REF].

Effects of fishing on reef fish assemblages

There are several reviews on the effects of fishing on reef ecosystems and fish populations: they consider many aspects such as size and life-history traits of target fish, the relative abundance of species or the trophic structure of the reef community [START_REF] Russ | Coral reef fisheries: effects and yields[END_REF][START_REF] Jennings | Population and ecosystem effects of reef fishing[END_REF][START_REF] Jennings | The effects of fishing on marine ecosystems[END_REF]. These impacts are difficult to assess and identify accurately and therefore remain "complex within a complex system" [START_REF] Sale | The science we need to develop for more effective management[END_REF].

The importance of life-history traits has already been proven in explaining fishing impacts on fish stocks. Lifehistory traits include fecundity, gestation period, growth rates, age-at-maturity, body size, longevity, natural mortality, dispersal ability, reproduction patterns and stage-specific habitat preferences [START_REF] Begg | The role of life history parameters as indicators of stock structure[END_REF]). These characteristics logically play a critical role in structuring reef fish populations subjected to fishing pressure: they may be directly related to reef fish vulnerability (Jennings et al. 1999b) and largely determine reef population resilience under exploitation. For example, the populations of large fish species decrease faster than those of smaller species as their life-history traits result in less resistance to fishing [START_REF] Denney | Life-history correlates of maximum population growth rates in marine fishes[END_REF], with the size selectivity of most fishing gears increasing this trend. In addition, while temperate marine fish are mainly gonochoristic, about 50% of tropical fishes are hermaphrodites, either simultaneous or sequential. Intense and size-selective removal may bias sex ratio in hermaphrodite species [START_REF] Sadovy | Reproduction of reef fisheries species[END_REF]. This effect is worsened by fishing on spawning aggregations where vulnerability is potentially increased by concentration or hunger [START_REF] Olsen | A study of a virgin islands grouper fishery based on a breeding aggregation[END_REF]. The knowledge of life-history traits is unfortunately far from sufficient for many reef fish species, although some attempts have been made to identify some generic lifehistory groups [START_REF] Kulbicki | Distribution of the major life-history strategies of coral reef fishes across the Pacific Ocean[END_REF].

Several variables have been proposed to assess changes due to fishing practice (Table 1). They may be grouped into two categories, 1) measurements (e.g. diversity, density, biomass, size spectrum); 2) grouping variables which make it possible to look at supra-species levels by, i) considering higher taxonomic levels (genera or families), ii) using biological or ecological criteria such as diet, size or behaviour, or iii) defining ecological functions (e.g. herbivores may be divided into grazers and browsers). The ability of communitybased indicators to track changes over time due to fishing is arguable. On one hand, their responsiveness allows detection of long-term changes and the effects of high fishing mortality [START_REF] Nicholson | Testing candidate indicators to support ecosystem-based management: the power of monitoring surveys to detect temporal trends in fish community metrics[END_REF]. Furthermore, they give a holistic answer to changes [START_REF] Mueter | Distribution of population-based indicators across multiple taxa to assess the status of Gulf of Alaska and Bering Sea ground fish communities[END_REF]. On the other hand, their interpretation can be controversial [START_REF] Rice | Environmental health indicators[END_REF]: the inaccuracy of the corresponding reference points or trends is high and they often fail to provide a simple and predictable link with fishing, in particular because of environmental fluctuations [START_REF] Rochet | Which community indicators can measure the impact of fishing? A review and proposals[END_REF]. Moreover they require more comprehensive data than population-level indicators on key species. On the contrary, these are sensitive to short-term fluctuations and species-specific impacts (e.g. recruitment) and as such can be unreliable or uninformative [START_REF] Fulton | Which ecological indicators can robustly detect effects of fishing?[END_REF]. They also raise major difficulties in comparing reef ecosystems with regard to species composition. The fact that one should find homogeneity in communitybased parameters across the Indo-Pacific is a strong argument in favour of grouping species for regional applicability, taking into account some local specificity [START_REF] Kulbicki | Basic principles underlying research projects on the links between the ecology and the uses of coral reef fishes en the Pacific[END_REF].

As an example, [START_REF] Graham | Sizespectra as indicators of the effects of fishing on coral reef fish assemblages[END_REF] showed that fishing usually first affects the largest species (which are also most targeted and have lowest recruitment and growth) using size spectra of the whole reef fish population. But size-age relationships do vary amongst coral reef fish species and can affect evidence of the impacts of fishing on the community size structure. Indeed, some species show a fast initial growth phase followed by a very slow size increase with age after first reproduction (e.g. Acanthuridae, Lutjanidae) [START_REF] Choat | Growth and longevity in acanthurid fishes: an analysis of otolith zones[END_REF][START_REF] Cappo | A new approach to validation of periodicity and timing of opaque zone formation in the otoliths of eleven species of Lutjanidae from the Central Great Barrier Reef[END_REF].

Competition and predator-prey interactions within the reef ecosystem have been investigated through selective fishing. The patterns of direct competition between grazing fish and urchins have been extensively studied in East Africa [START_REF] Mcclanahan | Kenyan coral reef lagoon fish: Effects of fishing, substrate complexity, and sea urchins[END_REF]). Pauly et al. (1998, 2002) and [START_REF] Christensen | Fishery-induced changes in a marine ecosystem: insight from models of the Gulf of Thailand[END_REF] have described long-term decreases in the average trophic level of the exploited communities that they ascribed to overfishing. [START_REF] Gascuel | The trophic spectrum: theory and application as an ecosystem indicator[END_REF] also proved that the trophiclevel-based approaches could be useful in analysing the impacts of fishing on the reef community. Despite this, in most CRF studies, prey abundance was not clearly related to the decline of piscivorous species [START_REF] Jennings | The effects of fishing on the diversity, biomass and trophic structure of Seychelles reef fish communities[END_REF][START_REF] Polunin | Differential effects of small scale fishing on predatory and prey fishes on Fijian reefs[END_REF][START_REF] Russ | Natural fishing experiments in marine reserves 1983-1993: community and trophic responses[END_REF] as has been observed in other ecosystems like freshwater lakes. [START_REF] Hixon | Predation as a process structuring coral reef fish communities[END_REF] hypothesised that this might come from the low specificity of the prey-predator linkage and "diffuse predation": this relation has to be very exclusive to detect any change in the prey populations [START_REF] Watson | Effect of an artisanal fishery on the fish and urchin populations of a Kenyan coral reef[END_REF]. However, predation seems to play a much stronger role at a small scale [START_REF] Jennings | The effects of fishing on marine ecosystems[END_REF] while fishing effects seem to be more constant at the level of the whole community.

Exploitation of reef resources

Coral reef fisheries are characterised as targeting multiple species with many gear types. These features are due to the range of targeted habitats and species, as well as being a response of the traditional skills and techniques developed, adopted and disseminated amongst fishers from Pacific island countries [START_REF] Dalzell | Coastal fisheries in the Pacific Islands. Ocean[END_REF]. About 200 species are currently targeted by Pacific coastal fisheries, but few dominate the catch. While the dominant species may change from one place to another, families are usually the same between countries and show similar characteristics in terms of response to fishing. Functional groups based on the diet of fishes can change their species composition from one place to the next, but maintain the same general ecological characteristics, allowing regional comparison of fishing impact.

CRF involve mainly artisanal fishing methods, which have been described in various studies (e.g. [START_REF] Munro | Assessment and management of coral reef fisheries: biological, environmental and economic impacts[END_REF][START_REF] Dalzell | Catch rates, selectivity and yields of reef fishing[END_REF][START_REF] Ruddle | Traditional management of reef fisheries[END_REF]. They comprise selective methods, such as hook and line, harpoon and spear, as well as non-selective ones such as fish fences, seines or gill-nets, sometimes including destructive ones, such as the use of explosives, poison or drive nets (e.g. McClanahan and Mangi 2004). Combinations of techniques vary according to target species and countries, but also within the same country according to area, time of year or type of fishery (commercial or subsistence). However, reef fishing generally involves relatively limited capital investment (small boats, some without motors, low-cost fishing gear) but large numbers of fishermen [START_REF] David | La petite pêche villageoise au Vanuatu, bilan d'un recensement[END_REF]. Previous surveys have proved that the more species a fishery targets, the less aggressive and thus the more sustainable it is [START_REF] Russ | Coral reef fisheries: effects and yields[END_REF].

There is little data on the dynamics of fishing communities and the behaviour of reef fishers. Pacific island reef resources have been continuously exploited for many centuries and, in parts of Melanesia, for millennia [START_REF] Dalzell | The role of archaeological and cultural-historical records in long-range coastal fisheries resources management strategies and policies in the Pacific Islands[END_REF]. Records suggest long-term stability of subsistence exploitation of finfish resources, stressing that recent changes may be more due to human behaviour, i.e. shifts in fishing strategies and availability of new technologies. Such changes include introduction of motorised boats combined with coastal population growth and new options for income generation. For instance, the live reef fish trade and the development of recreational fisheries have accelerated this trend.

Most of the exploitation-related characteristics of CRF must be estimated from landings and catch composition and from fishing effort information, i.e. fishing grounds, fishing time, fishing periods, gear and boat characteristics (Table 1). Evaluation and standardization of fishing effort data in such fisheries is a crucial but difficult and poorly investigated topic. It involves accurate assessment of the multiplicity of fishing with increasing fishing effort in the fence reef fishery in Rangiroa (French Polynesia). Data from EVAAM ranging form 1972 to 1986 (adapted from [START_REF] Chauvet | The coastal fisheries in French Polynesia[END_REF].

techniques, e.g. through spatial and seasonal patterns, fishing gears and target species [START_REF] Pelletier | Defining fishermen exploitation tactics from the analysis of logbooks and commercial sampling data[END_REF]. Qualitative changes such as the introduction of motorized boats are important to take into account as they enable access to better fishing grounds in terms of quantity and quality, and a wider choice of gears, timing and duration of fishing trips. The collection of such information is expensive compared to the value of the catch and, especially in the case of CRF, obtaining a representative sample is difficult and time consuming. Examples of regular creel surveys are available from Guam, American Samoa and Hawaii but the efficiency of these surveys need to be assessed [START_REF] Ault | Coral reef fish stock assessment workshop[END_REF]). The use of fish fences in the Tuamotu Archipelago may be an exception, as the fences are easily surveyed, with fish being removed only when traders visit the islands.

Stock assessment models such as virtual population analysis (see e.g. Hilborn and Walters 1992) have been recognised as insufficient in the face of ecosystem-based management [START_REF] Hilborn | Ecosystem-based fisheries management: the carrot or the stick?[END_REF]) and are also unsuitable for assessing mixed fisheries, such as CRF. Single-species stock assessment models have been tried for adapting traditional approaches such as dynamic pool models [START_REF] Schaeffer | Some considerations of population dynamics and economics in relation to the management of the commercial marine fisheries[END_REF] or surplus production models [START_REF] Fox | An exponential yield model for optimizing exploited fish populations[END_REF] to multispecific fisheries [START_REF] Kirkwood | Simple models for multispecies fisheries[END_REF][START_REF] Beddington | The limits to exploitation on land and sea[END_REF]. But these models are unfortunately not robust when subject to uncertainties in input data (e.g. [START_REF] Pelletier | Assessing the impact of sampling error on model-based management advice: comparison of equilibrium yield per recruit variance estimators[END_REF] and data scarcity in CRF is a shortcoming in this respect.

Furthermore, we agree with [START_REF] Hilborn | The dark side of reference points[END_REF] that data-based approaches are preferable than model-based ones to provide incentive information for fishers, scientist and managers. Particularly, estimations based on the average size or catch per unit of effort may prove useful in the CRF context. In Rangiroa Island for example (Fig. 2), fishing data analysis showed that an increase in fishing effort brought a decrease in catch per fence. Focusing on a few target species would allow reducing data collection thus making sampling more accurate on a representative and sensitive group of species.

Social and economic aspects of reef fisheries

Societies that have developed in association with coral reefs are often highly dependent on coastal resources for subsistence purposes, maintenance and reinforcement of social networking, and for informal insurance (Bataille-Benguigui 1981; [START_REF] Ruddle | The traditional knowledge and management of coastal systems in Asia and the Pacific[END_REF][START_REF] Bender | Fisher in the net: Strategies of resource use and conflict management in Ha'apai, Tonga[END_REF][START_REF] Bender | Informal insurance and sustainable management of common-pool marine resources in Ha'apai, Tonga[END_REF]. Small-scale fisheries may comprise commercial, subsistence and recreational fishing. These activities may overlap as their objectives are non-exclusive, but they may be separated according to their strategies, methods and catch use (Table 2). Assessment of their respective importance requires different approaches and a typology of fishers based on their fishing strategy [START_REF] Ferraris | Fishing fleet profiling methodology[END_REF]. In a great number of South Pacific societies, fishing as a source of protein remains a priority; many authors have stressed the linkage between human population size and pressure on the fish stocks [START_REF] Roberts | Rapid buildup of fish biomass in a Caribbean marine reserve[END_REF]Jennings and Polunin 1996a;[START_REF] Labrosse | Fish stock assessment of the Northern New Caledonian lagoons: 3-Fishing pressure, potential yields and impact on management options[END_REF]. The influence of population pressure on fish stock depletion has played a critical role in some islands with high demographic growth rates [START_REF] Mcmanus | Coral reef fishing and coral-algal phase shifts: implications for global reef status[END_REF]. However, recent studies have reduced the importance of this factor, which acts concurrently with dependency on marine resources, cultural importance of fishing, involvement in market economy and effectiveness of resource management (World Bank 2000).

The role of CRF in generating income has increased with the adoption of a cash-based economic system in Pacific island countries through the development of local, regional, national and international markets [START_REF] Iwariki | An introductory study of the socioeconomic aspects of household fisheries in the small islands economies of the South Pacific[END_REF][START_REF] Zann | The status and management of subsistence fisheries in the South Pacific[END_REF]. Higher incomes allow more and more people to buy fish instead of catching it themselves or bartering it. In contrast, international markets have mainly developed through specific demands for high value products, e.g. the live reef fish or the aquarium fish trades (e.g. [START_REF] Sadovy | The humphead wrasse, Cheilinus undulates: synopsis of a threatened and poorly known giant coral reef fish[END_REF]. As a result, the gradual increase in cash transactions has led to higher complexity in the CRF system: outside fishers (both national and foreign) have become involved in fishing grounds traditionally used by local fishermen; middlemen have emerged; at the same time, different factors, such as availability, prices of substitute products or the opportunistic cost of labour, have affected individual fisher behaviour. Three main factors slow down this shift to market-based systems: i) the poor quality of the distribution network; ii) the low cash capacity of potential consumers; and iii) socio-cultural constraints. Distribution of marine products is usually problematic due to geographical isolation, patchy density of population and lack of inexpensive land and sea connections. Sources of income often remain limited, particularly in small islands with restricted areas for agricultural production (which is often the main alternative source of cash in the Pacific).

Attempts have been made to link fishing pressure to variables such as demand for fish (ratio of consumed food from subsistence and from purchases, trade exchanges, market prices) or availability of alternative source of income (see Table 1). Fishing strategies practised in the context of subsistence and small-scale fisheries in the Pacific island countries do not necessarily follow profit maximising principles [START_REF] Kronen | Fishing for fortunes? A socio-economic assessment of Tonga's artisanal fisheries[END_REF]. In these cases, indicators that would be based on or linked to Western economic strategies are not appropriate. For Pacific islands, fish consumption most often depends on subsistence fishing since fish trading within and amongst islands is usually negligible. It also gives qualitative and quantitative information on target species, food habits and fishing practices as it has been illustrated in New Caledonia [START_REF] Labrosse | Fish stock assessment of the Northern New Caledonian lagoons: 3-Fishing pressure, potential yields and impact on management options[END_REF]Léopold et al. 2004). The factors controlling fish consumption were different in the two studies: ethnic group, age and geographical distribution prevailed in the Northern Province, whereas fishing practice, household income and size were the dominant drivers in Ouvea Atoll.

Under certain circumstances, population density (e.g. number of households or of people with fishing rights) has also been used as a proxy measurement of fishing pressure (e.g. [START_REF] Dulvy | Size structural change in lightly exploited coral reef fish communities: evidence for weak indirect effects[END_REF]). The involvement of women and children in these fisheries should be closely investigated as their contribution to finfish catch has often been underestimated [START_REF] Kronen | Women's fishing in Tonga: case studies from Ha'apai and Vava'u islands[END_REF]. Careful observation of fishers, including cultural and anthropological aspects, is necessary to obtain reliable information.

Assessment of coral reef fisheries through a multidisciplinary indicator dashboard

Assessment of coral reef health status has become an important issue in South Pacific islands where population growth, economic activities and the breakdown of marine tenure systems have increased risks of ecosystem degradation and fish over-exploitation. In particular, data-based fishery management faces major difficulty in taking into account biological, social and economic factors. A way to implement combined and multidisciplinary indicators in a participatory decisionmaking process is discussed.

The need for an ecosystem indicators framework

In most tropical coastal societies, a mixture of traditional and modern systems is interwoven, resulting in the co-existence of a variety of different fisheries systems [START_REF] Hunt | Cooperative approaches to marine resource management in the South Pacific[END_REF][START_REF] Hunt | Fiji's fisheries: their contribution to development and their future[END_REF]. While traditional or community-based management on the one hand, and centrally or government-managed systems on the other, are the possible extremes, recent efforts aim at co-management of marine resources [START_REF] Pomeroy | Conditions affecting the success of fisheries co-management: lessons from Asia[END_REF]. It is now generally recognised that success requires the involvement of fishery stakeholders as well as other users of the coastal zone [START_REF] Smith | Implementing effective fisheries-management systems. Management strategy evaluation and the Australian partnership approach[END_REF][START_REF] Walker | Resilience management in social-ecological systems: a working hypothesis for a participatory approach[END_REF][START_REF] Olsen | Frameworks and indicators for assessing progress in integrated coastal management initiatives[END_REF][START_REF] Mace | In defence of fisheries scientists, single-species models and other scapegoats: confronting the real problems[END_REF][START_REF] Zeller | The future of fisheries: from "exclusive" resource policy to "intrusive" public policy[END_REF]. Society participation and governance are fundamental principles of the ecosystem approach to fisheries [START_REF] Garcia | The ecosystem approach to fisheries. Issues, terminology, principles, institutional foundations, implementation and outlook[END_REF]. In fact, fisheries departments manage resources in ecological and economic contexts, while for local communities, moral and ethical dimensions can be more important and give an intrinsic value to the natural environment [START_REF]Pacific island peoples' science and marine management[END_REF]. This point is crucial and socio-cultural, institutional and political aspects are as relevant as ecological, economic or technical aspects for CRF management.

Useful indicators for environmental management have already been developed in a Driving force/Pressure/State/ Impact/Response framework (OECD 1993), which was then proposed as a possible organisation of the fisheries management system [START_REF] Caddy | Current usage of fisheries indicators and reference points, and their potential application to management of fisheries for marine invertebrates[END_REF]). This framework relies on a clear identification of causes and effects and aims at testing operational actions with respect to identified fisheries impacts and management guidelines. In the case of CRF, delayed response of indicators and their interactions preclude a good representation in this type of framework.

In this context, we propose a simple indicator framework that emphasises the capacity to assess the status and evolution of CRF using information derived from the three CRF system components. It should have the capacity to represent the junctions between the resources, the ecology of the exploited communities and their uses [START_REF] López-Ridaura | Evaluating the sustainability of complex socio-environmental systems, The MESMIS framework[END_REF]. Indeed, we agree with Berkes and Folke (1998) that monitoring ecosystem dynamics (including humans) is necessary to shape (adapted from FAO 1999;[START_REF] Kurtz | Strategies for evaluating indicators based on guidelines from the Environmental Protection Agency's Office of Research and Development[END_REF][START_REF] López-Ridaura | Evaluating the sustainability of complex socio-environmental systems, The MESMIS framework[END_REF]Belfiore 2003;[START_REF] Rice | Environmental health indicators[END_REF][START_REF] Rice | A framework for selecting a suite of indicators for fisheries management[END_REF]. management practices in response to changes. The goal is to present complex phenomena in a simple and accessible manner [START_REF] Bowen | Socio-economic indicators and integrated coastal management[END_REF].

Selecting a set of indicators

Indicators have to be selected with regard to specific management objectives like fisheries sustainability, habitat and wildlife conservation, and human acceptability. There are no standardised methods for assessing indicator quality. However, relevance and effectiveness criteria are generally mentioned [START_REF] Nicholson | Developing effective environmental indicators -does a new dog need old tricks?[END_REF][START_REF] Hauge | A framework for making qualities of indicators transparent[END_REF][START_REF] Rochet | Do explicit criteria help in selecting indicators for ecosystem-based fisheries management?[END_REF]. Relevance concerns the indicator meaning, scientific basis and sensitiveness to the questions of managers, while effectiveness encompasses precision and feasibility (technical ability, data availability, costs). In a management perspective, CRF indicators should be sensitive to fishing impacts in the short to medium term [START_REF] Nicholson | Testing candidate indicators to support ecosystem-based management: the power of monitoring surveys to detect temporal trends in fish community metrics[END_REF]) and helpful to quantify these impacts. Issues such as data requirements, uncertainty estimation and robustness under various changes are also recognised as important [START_REF] Kurtz | Strategies for evaluating indicators based on guidelines from the Environmental Protection Agency's Office of Research and Development[END_REF][START_REF] Walker | Resilience management in social-ecological systems: a working hypothesis for a participatory approach[END_REF][START_REF] Trenkel | Performance of indicators derived from abundance estimates for detecting the impact of fishing on a fish community[END_REF].

To detect trends and assist decision-making, indicator values should be periodically reported. The monitoring programme design depends on a number of factors such as the speed of change of the ecosystem in response to human impacts, the local management objectives (e.g. statistical power to detect a 10% decrease in abundance, cost of false alarms, etc.), and funding (sampling costs, time scale, etc.). Closer attention is needed in case of rapid change to the CRF system to allow for early warnings.

In this respect, involving local resource users in monitoring is challenging. It is seen as a promising way to avoid expensive field surveys, to help in early change detection, to build incentives to learn about environment processes and finally to improve management success [START_REF] Tawake | Harvesting clams and data[END_REF][START_REF] Olsson | Adaptative comanagement for building resilience in social-ecological systems[END_REF]. But because traditional monitoring (e.g. fishers measure their own catch and yields) focuses on sites and/or periods of high catchability, it should be carefully calibrated against spatially and temporally unbiased scientific methods before its implementation [START_REF] Moller | Combining science and traditional ecological knowledge: monitoring populations for co-management[END_REF]). Changes in abundance that are linked to the dynamics and the spatial variability of resources control their availability for fishers and need to be more effectively taken into account in assessing fishing impacts.

Several authors have already proposed formal operational frameworks for stakeholders to facilitate indicator selection among candidate variables (Table 3). A single indicator cannot account for fisheries and ecosystem complexity, but the number of potential indicators is reduced in data-limited management situations [START_REF] Johannes | The case for data-less marine resource management: examples from tropical nearshore finfisheries[END_REF], such as in the South Pacific. Identifying the major issues for the target users groups is the first step as their participation is required long before the implementation phase. Indeed, the correspondence between indicator values and management actions to be undertaken should be clearly specified. Dialogue has to be encouraged during indicator selection in order to reach consensus and explicit agreement on data supply and common standards [START_REF] Bonzon | Development of economic and social indicators for the management of Mediterranean fisheries[END_REF].

The chronic scarcity of data on resources and fishing activities with high intrinsic variability and the need for a participative monitoring of the CRF system can lead to inaccurate indicator values and inadequate surveys. Following [START_REF] Seijo | Uncertainty in bio-economic reference points and indicators of marine fisheries[END_REF], our concern relates to complementary or partially redundant indicators based on independent data sets Table 4. An example of an indicator dashboard of the Coral Reef Fisheries system of Ouvea Island, South Pacific. Ecological data are synthesised in [START_REF] Kulbicki | Evaluation des resources en poisons du lagon d'Ouvéa. 3 e partie : les poissons[END_REF]. All fish > 5 cm length were counted along 164 transects of 50 m by two experimented divers. Fishing, consumption and economical data are adapted from Léopold et al. 2004. The field surveys, which were conducted during this study also, allow us to give qualitative user scores to indicator values though specific questions on these indicators have not been asked during interviews. All values are satisfactory (indicated by ) concerning subsistence and recreational fishers. Low scores for commercial fishers are indicated by △ ! .

( * ) Lagoon and reef communities are distinguished by species composition, size and biomass which are all different between the two biotopes. ( * * ) Subsistence, commercial and recreational target species are almost similar in Ouvea Island as handline fishing is widely practiced by the three fisher categories. Data includes all species of families Acanthuridae, Carangidae, Labridae, Lethrinidae, Lutjanidae, Priacanthidae, Scaridae, Scombridae, Serranidae, Siganidae, and Sphyraenidae. ( * * * )Fish< 20 cm are usually not targeted. Density of recruited fish is much less sensitive to variations of annual recruitment than density of fish of all sizes. The ratio is linked to the abundance of large fish in the population of fish > 20 cm.

(see below) to counterbalance sampling error and improve decision-making.

The assessment process through an indicator

dashboard -A case study

The added-value of a fisheries assessment dashboard

A formal assessment dashboard of Ouvea Atoll fishery in New Caledonia has been built from the information obtained from an underwater visual census [START_REF] Kulbicki | Evaluation des resources en poisons du lagon d'Ouvéa. 3 e partie : les poissons[END_REF]) and field surveys (Léopold et al. 2004). No management plan has been implemented in this unspoilt atoll where human pressure is still low. Over the 20 villages of the island, Melanesian people representing over 97% of the total population, still pursue a traditional lifestyle.

The proposed dashboard is composed of three types of data (Table 4):

• An indicator set of complementary variables that could describe the situation of this South Pacific coral-reef fishery; • The indicators' estimated values;

• The user scores which express the fishers' perception of each indicator according to their own interests.

Indicator values have to be interpreted in comparison to preset reference points, which can be temporal means, first assessment values, target values or thresholds [START_REF] Rice | Environmental health indicators[END_REF]. They should refer to agreed objectives among users even if they neither attach equal importance to the selected indicators nor share the same interests (Table 2). For example, a biodiversity indicator will not be judged in the same way by commercial and subsistence fishers, because the former focus on higher value species while the latter are usually interested in a larger pool of fish and invertebrates (Jennings and Polunin 1996b;[START_REF] Jennings | Population and ecosystem effects of reef fishing[END_REF]. The user scores can be defined in relation to the "traffic light" method, where indicators are green (safe status), orange (status needing improvement), or red (dangerous status): trends in colours depend on the system evolution and are easily understood [START_REF] Caddy | A short review of precautionary reference points and some proposals for their use in data-poor situations[END_REF]. Such a dashboard gives a synoptic assessment of CRF status and should be completed at regular intervals, e.g. on an annual or a seasonal basis. It adds value to the indicator monitoring part (values and references) thanks to its operational and decision-making characteristics. It helps coordination between different user types explicitly presenting their areas of interest and concessions according to management objectives. This kind of assessment table has already been proposed for coastal water quality management, which concerns another common and highly coveted resource [START_REF] Beliaeff | Système d'évaluation de la qualité des eaux littorales : grille d'aptitude aux usages et à la biologie[END_REF].

Description of the selected indicator set

In our practical example of the Ouvea reef fishery, the dashboard includes eleven indicators (Table 4) on commercial fisher activity (3 parameters), household fish consumption (3), fish trade (3) and target species populations [START_REF] Ferraris | Fishing fleet profiling methodology[END_REF]. This selection was based on empirical knowledge and references from literature, but indicator quality criteria (particularly responsiveness and robustness (Table 3) should be tested on these variables for statistical validation.

The ecology component is based on total counts of fish populations and requires specialists in underwater visual census. We propose to combine data on size and abundance of recruited fish:

• density of fish greater than 20 cm (which is about the recruited size for most target species), and • proportion of large individuals (greater than 40 cm) in the community of recruited fish.

Changes and trends in these measurements can accurately reflect effects of fishing on the community [START_REF] Nicholson | Testing candidate indicators to support ecosystem-based management: the power of monitoring surveys to detect temporal trends in fish community metrics[END_REF][START_REF] Jennings | Reference points and reference directions for sizebased indicators of community structure[END_REF][START_REF] Shin | Using size-based indicators to evaluate the ecosystem effects of fishing[END_REF]. More particularly, data on the Emperor Lethrinus nebulosus and the Blue Maori Epinephelus cyanopodus, which are two iconic species of the fishery and are included in the two composite indicators, are of great value in making people aware of marine resource status. The exploitation component does not refer to all fishing activities as global catch and effort data are difficult to gather. For efficiency reasons, we focus on data from 23 reliable and active key-fishermen producing for sale, who try to maximise the catch and time spent at sea ratio: 1) species composition of catch (to detect switch in target species), 2) catch level, and 3) effort level per fishing gear. Their fishing yields can immediately be deduced from these data and add a complementary index of fish abundance in Ouvea lagoon.

Lastly, the social and economic component is based on household and market surveys to estimate fish trading on and off Ouvea Island and to describe the structure of fish consumption quantitatively and qualitatively. The reliability of this consumption-based approach depends on the accuracy of estimates of fish imports and exports. Thus, five indicators have been kept in Table 4: 1) composition of fish consumption (to detect changes in available resources on the shoreline where most people fish for their own needs), 2) level of fish consumption (to assess food dependency on marine ecosystems), 3) origin of consumed fish (to assess the development of the cash market), 4) fish exports (in-kind gifts sent overseas and sales off-island) and 5) fish imports.

The fishing-sensitive indicator set combines information of different kinds and should achieve a balance between a CRF system description and early change detection. The fish resource is tracked from its natural environment to its use by islanders.

Decision-making process and management options

In the case of Ouvea fishery, where no management plan is yet in place, it was difficult to scale or score the selected indicators as no reference point is presently available for any of them. The present values are the first available estimations of indicators and can thus be baseline values from which changes and trends will be assessed.

The last section of the dashboard deals with the user scores and aims at translating indicator values into decision-making criteria [START_REF] Link | Translating ecosystem indicators into decision criteria[END_REF]. Three kinds of resource users have been distinguished on Ouvea atoll, but a fisher typology would be required to precisely identify interest groups:

• Subsistence fishermen target any edible species usually close to the sea-shore, mainly Lethrinidae, Serranidae and Gerreidae, using any kind of gear. Nine out of ten households are concerned. • A minority of commercial fishermen land less than 10% of total catch, mainly Lethrinidae, Serranidae and schooling fish (Mugilidae, Scombridae). • A few recreational fishermen are also present on the island.

For academic purposes, the user scores were derived from individual interviews; a real management process should involve all members and leaders of the fisher communities in a participatory way. All indicator values are judged satisfactory by the surveyed subsistence and recreational fishers whereas commercial fishers clamed that they would rather appreciate financial support to increase their fleet capacity to target deeper or pelagic species, and to improve the distribution network to export fish to urban areas (Table 4).

These responses can be interpreted as the following management objectives:

• keep reef biodiversity and shoreline resources to their present status to ensure food security, ecosystem health and recreational business, and

• slightly develop professional fishing to better exploit the island's economic potential.

Therefore, the completed dashboard works as a picture of Ouvea coral-reef fishery from different kinds of users: it is a visual transcription that jointly indicates which stakeholders complain about the situation and which issues should be addressed. This process stresses which discussions and negotiations should focus on making decisions transparent and being a hindrance to lobbies.

In the above example, the dashboard construction and analysis were limited to fish resource users because of data limitations. A full ecosystem approach to CRF requires involving other stakeholders such as other user groups, managers, politicians, scientists, and the public. Hence, the indicators of environment and fisheries status should be considered in the context of a broad governance system, including political and institutional partners. In particular, information on the organisations or institutions regulating access to fisheries is crucial (level of involvement of stakeholders, decision process, etc.), as well as an indication of the degree to which existing regulations are effectively applied.

Conclusion

Coral reef fisheries are obviously highly diverse systems, mainly due to the biodiversity of marine species and habitats, social and economic traits and island geographical settings. They play a critical role for protein supply particularly in small-island developing nations, but often enjoy only limited support for research and assessment. In this context of limited financial and human resources, their future sustainability depends on improved management capability. The devising of efficient and easy-to-use management tools should be bas a multidisciplinary approach and ii) the selection of relevant and complementary indicators.

Some research has been carried out in a limited number of South Pacific islands since 2001 to understand key relationships between resource characteristics, fisher activities and socio-economic features in CRF systems [START_REF] Ferraris | Les pêcheries récifales dans le Pacifique sud : d'une gestion intuitive vers une gestion écosystémique raisonnée[END_REF]. In this paper, we have proposed to gather independent and complementary indicators in a synoptic dashboard. The indicator set would provide reliability to the diagnoses on the overall system by local groups despite a possible lack of accuracy of individual variables. The functioning and implications of the dashboard approach have been described through an academic fishery assessment by fisher groups using a case study.

This step may be a way to achieve participatory monitoring and management of CRF given that both data updating and indicator scoring rely on stakeholder involvement. We think that the co-management challenge depends on key information being provided to decision-makers. Further development is still required to find indicators that achieve research-based validity and match local stakeholder knowledge and skills [START_REF] Degnbol | Indicators as a means of communicating knowledge[END_REF]. Scientific studies are needed 1) to assess the performance of the dashboard indicators in terms of sensitivity, accuracy, temporal and spatial representativeness and specificity, and 2) to provide local populations with workable and robust monitoring methods. These commonly-gathered data would help conventional managers make decisions not entirely based on their own perception of the resources and fishing activities.

Fig. 1 .

 1 Fig. 1. Multidisciplinary framework for assessing resource status and level of exploitation in a CRF system. Resource status depends on both ecosystem factors and human factors. For each system component, examples of usual variables for assessing the status and dynamics of the fishery linked to these factors are listed.

Fig. 2 .

 2 Fig.2. Evolution of catch per unit effort (in kg fence -1 , all species) with increasing fishing effort in the fence reef fishery in Rangiroa (French Polynesia). Data from EVAAM ranging form 1972 to 1986 (adapted from[START_REF] Chauvet | The coastal fisheries in French Polynesia[END_REF].

Table 1 .

 1 Variables commonly used to assess disciplinary aspects of fishery systems and applicable to Coral Reef Fisheries. Listed variables are considered as potential indicators. Ecological variables are measured at the level of the population or community.

Table 2 .

 2 Basic typology of fishermen in South Pacific CRF.

Table 3 .

 3 Framework for selecting and scoring indicators

Acknowledgements. This work is a contribution to the Nouméa indicator workshop held in July 2002 with a grant from the French National Coastal Environment Program (PNEC). We would like to thank the translators and referees for their constructive comments.


D Bellan-Santini

European species of Haustorius (Crustacea: Amphipoda: Haustoriidae), with description of a new Mediterranean species

Keywords: Amphipoda, Haustoriidae, Haustorius orientalis, Mediterranean, new species

The genus Haustorius is represented by six species in the world; three are described as American species, three European including a new species described from the Mediterranean. This new species, H. orientalis, is similar to H. algeriensis Mulot, 1967 from the Algerian coast but differs in rostrum slightly exceeding in length the antennal lobes, merus of pereiopod 7 with posterior margin lacking spines, and uropod 1 with two separate rows of spines.

Introduction

The genus Haustorius Mu ¨ller, 1775 is now represented by five valid described species: Haustorius arenarius (Slabber, 1769), H. canadensis Bousfield, 1962, H. algeriensis Mulot, 1967, H. jayneae Foster and Lecroy, 1991, and H. mexicanus Ortiz, Chazaro-Olvera and Winfield, 2001. When in 1967, Mulot described H. algeriensis from the Algerian coast, he indicated that this species was the first Haustorius found in the Mediterranean sea and it remains unique [START_REF] Bellan-Santini | The Amphipoda of the Mediterranean, Part 2[END_REF]) and has never been sampled beyond its type locality of Sidi Fredj region: Bou Ismail Bay, Djinet Cape [START_REF] Bakalem | Inventaire des Crustace ´s Amphipodes (Gammaridea, Caprellidea, Hyperiidea) des co ˆtes d'Alge ´rie. Essai de synthe `se[END_REF]. A new species collected on a beach at Michmoret (Israel coast) presents significant differences with the other species, and in particular with H. algeriensis. It brings the number of Haustorius to six species with three of them European.

Taxonomy

Haustorius orientalis n. sp.

(Figures 12345)

Material examined

Holotype: one female of 6 mm; paratypes: 24 specimens (seven of them are females with oostegites), Museo Civico di Storia naturale Verona (MVRCr 429).

Type locality

Michmoret beach (Israel coast), in the sand in the upper part of infralittoral zone.

Diagnosis

Body broad. Head with rostrum exceeding slightly the antennal lobes. Pereiopod 5 with rounded basis, fringed with long setae, ischium short, merus enlarged, spinose on the surface, fringed with spines and plumose setae, carpus less enlarged than merus, very spinose, propodus very spinose on the anterior margin and with five distal spines. Pereiopod 6, basis rounded, fringed with long setae, ischium short, merus expanded with numerous spines on the surface and on the margins, long plumose setae on the anterior and distal margins, carpus subquadrate covered and fringed with spines, propodus fringed at the posterior margin with spines, seven distal spines. Pereiopod 7, basis large, anteriorly fringed with plumose setae, ischium short, merus produced posteroventrally, anterior margin spinose on the distal half, distal margin spinose, posterior margin without spines, fringed with long plumose setae, carpus and propodus fringed with many spines, short setae on the surface of the carpus. Epimeron 2 with the distal posterior corner quadrate. Epimeron 3 rounded posteriorly, without process, with long plumose setae on the surface. Uropod 1 rami unequal, peduncle and rami armed with strong spines, peduncle with two rows of four spines. Uropod 2, rami unequal, outer ramus longer than inner, peduncle and rami fringed with long setae. Uropd 3, peduncle shorter than rami, outer ramus longer than inner biarticulate, long setae on the distal margin. Telson cleft to the base, consisting of two widely separated lobes with two lateral and 12 distal long setae, two plumose setae on each lobe.

Etymology

The specific name refers to the region of the type locality, in the oriental basin of the Mediterranean.

Relationship

The different species of Haustorius differ from each other in the shape of the rostrum, uropod 1 and pereiopod 7 (denoted 5 by [START_REF] Bousfield | Haustoriidae of new England (Crustacea: Amphipoda)[END_REF][START_REF] Mulot | Description d'Haustorius algeriensis n. sp. (Amphipoda, Haustoriidae)[END_REF]. The three European species differ from the American ones essentially in the merus of P7, which has the proximal margin continuous with the posterior margin. It is sharply set off from posterior margin in American species (Barnard and Karaman 1991; Foster and Lecroy 1991) (Figure 5). Among the three European species, the Atlantic H. arenarius has a five-articulate accessory flagellum and the merus of P7 with three to four stiff spines groups at the posterior margin. The two other European species are Mediterranean. Haustorius orientalis differs from H. algeriensis in the rostrum exceeding slightly the antennal lobes (equal in length in H. algeriensis), the flagellum of A2 eight-articulate (nine-articulate in H. algeriensis), the third article of the mandibular palp with a comb of 17 small setae (14 in H. algeriensis), the merus posterior margin of P7 not spinose (three spines in H. algeriensis), and the peduncle of U1 with two clusters of four spines on the ventral margin (a row of spines in H. algeriensis). -P7, merus, posterior margin lined continuously straight without spines at the distal part. U1 peduncle with two clusters of four spines on the ventral margin . . . .....................

Key to the European

.H. orientalis

Comments

There are two groups of described Haustorius: the American and the European groups. The American has three species H. canadensis, H. jayneae and H. mexicanus. They have in common a strong character concerning the merus of pereiopod 7 with the proximal margin sharply set off from posterior margin (Figure 6: 3,4,5). [START_REF] Foster | Haustorius jayneae, a new species of Haustoriid Amphipod from the Northern gulf of Mexico, with notes on its ecology at Panama city Beach, Florida U.S.A[END_REF] report also a great number of undescribed haustoriid species as pointed out by [START_REF] Bousfield | Adaptative radiation in sand-burrowing amphipod crustaceans[END_REF], [START_REF] Fox | The amphipod crustaceans of North Carolina estuarine[END_REF] and [START_REF] Thomas | A survey of gammarid amphipoda of the Barataria Bay, Louisiana region[END_REF].

For the European coast, three species of Haustorius have been described: Hautorius arenarius distributed from the Norwegian coast to Morocco [START_REF] Moore | The fauna of the Clyde sea area Crustacea: Amphipoda. Millport, Isle of Cumbrae: University Marine Biological Station[END_REF][START_REF] Menioui | Contribution a `la connaissance des Amphipodes gammariens de la co ˆte atlantique du Maroc[END_REF][START_REF] Palerud | Marine Amphipoda Gammaridea in North-East Atlantic and Norwegian Arctic[END_REF][START_REF] Dauvin | Mise a `jour de la liste des espe `ces d'Amphipodes (Crustacea: Peracarida) pre ´sents en Manche[END_REF][START_REF] Bellan-Santini | European Register of Marine Species: a checklist of the marine species in Europe and a bibliography of guides to their identification[END_REF][START_REF] Cherkaoui | Organisation spatiale des peuplements macrozoobenthiques subtidaux d'un estuaire de la co ˆte atlantique marocaine: l'estuaire du Bou Regreg[END_REF][START_REF] Dauvin | Biodiversity and the biogeographic relationships of the Amphipoda Gammaridea along the French coastline[END_REF]; Haustorius algeriensis, distributed on the Algerian coast from Bou Ismail Bay to Cap Djinet [START_REF] Mulot | Description d'Haustorius algeriensis n. sp. (Amphipoda, Haustoriidae)[END_REF][START_REF] Bakalem | Inventaire des Crustace ´s Amphipodes (Gammaridea, Caprellidea, Hyperiidea) des co ˆtes d'Alge ´rie. Essai de synthe `se[END_REF]; and Haustorius orientalis n. sp. described from the Israeli coast, Michmoret beach (near Netanya).

The three European species are close with a merus of the pereiopod 7 with proximal margin rounded, continuous with posterior margin (Figure 6: 1, 2, 6).

On the ecology of these species little is known for H. algeriensis and H. orientalis. The two species live in sandy beaches as other Haustorius, at the upper infralittoral level, between 0 and 25 m for H. algeriensis [START_REF] Bakalem | Inventaire des Crustace ´s Amphipodes (Gammaridea, Caprellidea, Hyperiidea) des co ˆtes d'Alge ´rie. Essai de synthe `se[END_REF] and with another peracarid species, a Mysidea, probably Gastrosaccus for H. orientalis (P. Chevaldonne ´, personal communication). For H. arenarius interesting data are believed by different authors. [START_REF] Vader | Intertidal distribution of Haustoriid Amphipods in the Netherlands[END_REF], on the Elbe estuary populations, considers that this species is euryhaline, it lives on exposed shores at the intermediate zone and shows a preference for coarse sand with 50% or less of sediment finer than 210 mm. For [START_REF] Moore | The fauna of the Clyde sea area Crustacea: Amphipoda. Millport, Isle of Cumbrae: University Marine Biological Station[END_REF], in the Clyde sea area, it ''is confined to upper half of intertidal area and prefers rather loose sand' '. Dennell (1933) considers this species to be a burrowing and filter feeder. [START_REF] Cherkaoui | Organisation spatiale des peuplements macrozoobenthiques subtidaux d'un estuaire de la co ˆte atlantique marocaine: l'estuaire du Bou Regreg[END_REF] give more complete information on the population of the Bou Regreg estuary (Morocco). H. arenarius was sampled in stations between 0.5 and 6 m; with fine sand with 0.2-10.2% of silt ,63 mmand 2.58-2.68% of organic matter, the salinity is normal at 34.7 PSU. The H. arenarius community is composed of two assemblages dominated, respectively, by Gastrosaccus spinifer and Solen marginatus.

Figure 1 .

 1 Figure 1. Haustorius orientalis, habitus. Scale bar: 1 mm.

Figure 2 .

 2 Figure 2. Haustorius orientalis: antenna 1 (1); antenna 2 (2); maxilla 2 (3); mandible (4); rostrum (5). Scale bar: 100 mm.

Figure 3 .

 3 Figure 3. Haustorius orientalis: lower lip (1); upper lip (2); maxilliped (3); gnathopod 1 (4); gnathopod 2 (5); maxilla 1 (6). Scale bar: 100 mm.

Figure 4 .

 4 Figure 4. Haustorius orientalis: pereiopod 3 (1); pereiopod 4 (2); pereiopod 5 (3); uropod 1 (4); uropod 2 (5); uropod 3 (6). Scale bar: 100 mm.

Figure 5 .

 5 Figure 5. Haustorius orientalis: pereiopod 6 (1); pereiopod 7 (2); coxa 2 (3); coxa 3 (4); telson (5). Scale bar: 100 mm.

  Haustorius species[START_REF] Foster | Haustorius jayneae, a new species of Haustoriid Amphipod from the Northern gulf of Mexico, with notes on its ecology at Panama city Beach, Florida U.S.A[END_REF] modified) 1. P7 merus, proximal margin sharply set off from posterior margin American species -P7 merus, proximal margin rounded continuous with posterior margin (European species) ......................2 2. Accessory flagellum with four segments; P7 merus, posterior margin with three to four stiff spines . . ...............H. arenarius -Accessory flagellum three-segmented..............3 3. P7, merus, posterior margin lined continuously but rounded with three spines at the distal part. U1 peduncle with a row of spines on the ventral margin . . . ..................... H. algeriensis

Figure 6 .

 6 Figure 6. Pereiopod 7: Haustorius orientalis n. sp. (1); H. algeriensis from Bellan-Santini et al. (1989) (2); H. jayneae from Foster and LeCroy (1991) (3); H. canadensis from Bousfield (1960-61) (4); H. mexicanus from Ortiz et al. (2002) (5); H. arenarius from Sars (1895) (6).

Acknowledgements

I thank Maoz Fine who has collected this material and Pierre Chevaldonne ´who gave it to me.