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Information on ocean scale drivers of methylmercury levels and variability in tuna is scarce, yet crucial in the context of anthropogenic mercury (Hg) inputs and potential threats to human health. Here we assess Hg concentrations in three commercial tuna species (bigeye, yellowfin, and albacore, n = 1000) from the Western and Central Pacific Ocean (WCPO). Models were developed to map regional Hg variance and understand the main drivers. Mercury concentrations are enriched in southern latitudes (10 degrees S-20 degrees S) relative to the equator (0 degrees-10 degrees S) for each species, with bigeye exhibiting the strongest spatial gradients. Fish size is the primary factor explaining Hg variance but physical oceanography also contributes, with higher Hg concentrations in regions exhibiting deeper thermoclines. Tuna trophic position and oceanic primary productivity were of weaker importance. Predictive models perform well in the Central Equatorial Pacific and Hawaii, but underestimate Hg concentrations in the Eastern Pacific. A literature review from the global ocean indicates that size tends to govern tuna Hg concentrations, however regional information on vertical habitats, methylmercury production, and/or Hg inputs are needed to understand Hg distribution at a broader scale. Finally, this study establishes a geographical context of Hg levels to weigh the risks and benefits of tuna consumption in the WCPO.

International audience; This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus uses different habitats throughout its life (mainly juvenile and adult phases). Of the most informative trace elements within otoliths (the twelve isotopes 23Na, 25Mg, 43Ca, 55Mn, 59Co, 60Ni, 63Cu, 66Zn, 86Sr, 111Cd, 138Ba and 208Pb) only three ratios of Ca (Na:Ca, Sr:Ca and Ba:Ca) were informative and therefore used in a multivariate regression-tree analysis. Using a multivariate partitioning, three main phases were described from profiles, including the larval life phase (leptocephali), the intermediate phase (longest section between the larval life phase and the terminal phase) and the terminal phase (final section i.e., the most recent months preceding the death of fish). According to concentrations of the three ratios to Ca, G. chilospilus can be separated into three groups during their larval life stage (very different in Sr and Na), four groups during the intermediate phase (few differences in Sr and Na) and three groups during the terminal phase (differences in Sr), illustrating that G. chilospilus inhabit different habitats during these three phases. Our results showed that the leptocephali encountered different oceanic water masses with fluctuating Sr:Ca ratios during the early larval phase. During the intermediate phase (main part of their life-span), they lived in lagoonal waters such as fringing reefs or reef flats of lagoonal islets, characterized by a lower Sr:Ca ratio. During the latter part of their life, approximately one third of G. chilospilus encountered more oceanic waters close to or at barrier reefs, suggesting possible movements of these fish along a coast-to-ocean gradient.

Deposit-feeding sea cucumbers are efficient nutrient recyclers and have the potential to contribute to the limitation of organic matter load in polyculture or integrated aquaculture systems. Assessing how they assimilate organic matter originating from other farmed species is therefore important for the development of such multi-species farming systems. Here, a coupled stable isotope − fatty acid approach was used to characterize the assimilation of organic matter from shrimp (Penaeus stylirostris) farming by Holothuria scabra in an experimental culture system. H. scabra were reared in mesocosms on shrimp farming-originating sediment with and without additional food sources (maize and fish meals). Although fatty acid results did indicate that shrimp-farming sediment was assimilated by holothurids, we found no evidence of maize waste and fish meal contribution to H. scabra organic carbon (no effect on δ13C, no accumulation of meal-specific fatty acids). However, a strong effect of fish meal on H. scabra δ15N was observed, suggesting that this additional food source could represent an alternative source of nitrogen for holothurids. Finally, this study supports the culture of H. scabra as a perspective to reduce sedimentary organic matter excess associated with shrimp farms, and suggest that the addition of selected food sources might contribute to increasing the content in some nitrogen organic compounds in holothurid tissues.

International audience; Moray eels form a speciose lineage that belongs to Elopomorpha, a super-order with a worldwide distribution.As is the case for many anguilliform fish, moray eels are characterized by distinctive life history traits, notably aprolonged larval dispersal phase that determines settlement to distant reef habitats, thus influencing the spatialstructuring of their populations. They can be very abundant in coral reef ecosystems and represent major mesopredators,playing a crucial role in food webs. Yet, due to their elusive nature (i.e. cryptic behaviour, nocturnalactivity), these organisms are generally difficult to study and collect. To our knowledge, only a few studies performedover large geographical and phylogenetic scales have been conducted. We used a unique and cost-efficientsampling approach, involving forced regurgitation from sea snake predators, to collect large numbers of a widespreadmoray eel species (Gymnothorax chilospilus). When combined with the development of 11 new microsatellitemarkers, this efficient sampling technique allowed us to examine the genetic structure of Gymnothoraxpopulations occurring in the South Lagoon of New Caledonia. Analyses revealed a lack of genetic differentiationamong populations. This result echoes the strong genetic homogeneity of populations of their main predator, thesea snake. This convergence might result from a distinctive trait involved in population functioning of both morayeels and sea snakes, where immature individuals emerge from common breeding grounds and disperse over longdistances before settlement.

The degradation of coral reefs is widely reported, yet there is a poor understanding of the adaptability of reef fishes to cope with benthic change. We tested the effects of coral reef degradation on the feeding plasticity of four reef fish species. We used isotopic niche sizes and mean δ15N and δ13C values of each species in two coral reefs that differed in benthic condition. The species chosen have contrasting feeding strategies; Chaetodon lunulatus (corallivore), Chrysiptera rollandi (zooplanktivore), Halichoeres melanurus (invertivore) and Zebrasoma velifer (herbivore). We predicted that the corallivore would have a lower mean δ15N value and a smaller isotopic niche size in the degraded reef, that the herbivore and the invertivore might have a larger isotopic niche size and/or a different mean δ13C value, whereas the zooplanktivore might be indifferent since the species is not linked to coral degradation. Some results matched our predictions; C. lunulatus had a smaller niche size on the degraded reef, but no difference in mean δ15N and δ13C values, and H. melanurus displayed an increase in niche size and a lower mean δ15N value on the degraded reef. Some other results were contrary to our predictions; whereas Z. velifer and C. rollandi had smaller mean δ13C values but no difference in niche size. Our findings suggest there may be feeding plasticity to maintain a similar diet despite contrasting habitat characteristics, with different amplitude depending on species. Such findings suggest that certain species guilds would probably adapt to changes linked to habitat degradation.

International audience; Estimates of trophic position are used to validate ecosystem models and understand food web structure. A consumer's trophic position can be estimated by the stable nitrogen isotope values (delta N-15) of its tissue, once the baseline isotopic variability has been accounted for. Our study established the first data-driven baseline delta N-15 isoscape for the Western and Central Pacific Ocean using particulate organic matter. Bulk delta N-15 analysis on 1039 muscle tissue of bigeye and yellowfin tuna were conducted together with amino acid compound-specific delta N-15 analysis (AA-CSIA) on a subset of 21 samples. Both particulate organic matter and tuna bulk delta N-15 values varied by more than 10 parts per thousand across the study area. Fine-scaled trophic position maps were constructed and revealed higher tuna trophic position (by similar to 1) in the southern latitudes compared to the equator. AA-CSIA confirmed these spatial patterns for bigeye and, to a lesser extent, yellowfin tuna. Using generalized additive models, spatial variations of tuna trophic positions were mainly related to the depth of the 20 degrees C isotherm, a proxy for the thermocline behavior, with higher tuna trophic position estimates at greater thermocline depths. We hypothesized that a deeper thermocline would increase tuna vertical habitat and access to mesopelagic prey of higher trophic position. Archival tagging data further suggested that the vertical habitat of bigeye tuna was deeper in the southern latitudes than at the equator. These results suggest the importance of thermocline depth in influencing tropical tuna diet, which affects their vulnerability to fisheries, and may be altered by climate change.

Carbon and nitrogen stable isotopes were used to describe an estuarine mangrove food web in New Caledonia, SW Pacific. Isotopic values were measured for all components of the ecosystem, from various organic matter (OM) sources to predators. Primary producers showed δ13C values from −32.29‰ (Bruguiera gymnorhiza) to −24.67‰ (mouth particulate organic matter), whereas δ15N values ranged from 1.48‰ (Avicennia marina) to 10.17‰ (Eichomia crassipes). Two potential organic matter sources, i.e. the mangrove species and E. crassipes, appeared not to be directly used by consumers although were indirectly entering the food web through particulate and sedimentary organic matter pools (POM and SOM). Overall, invertebrates showed C-depleted and N-depleted values compared with fish, highlighting their lower trophic level. The highest trophic levels in this estuarine mangrove were represented by carangids (δ15N of 11.24‰ for Caranx sp. and 10.81‰ for Carangoides fulvoguttatus) and gerrids (δ15N of 10.42‰ for Gerres filamentosus). Two main pathways of organic matter were identified from sources of OM to end-members, i.e. from estuarine POM and SOM toward gerrids and from marine POM towards carangids. The food chain comprised three or four trophic levels, depending on the pathway of organic matter. The position of some consumer species within the reconstructed food web might imply that an important source of organic matter was probably missing, i.e. microphytobenthos. Despite an obvious connection, the role of river inputs as potential drivers of mangrove food web dynamics appeared important only during the wet season.

This study was conducted to compare the effects of shrimp and rabbitfish in mono- and polyculture stocked at high biomass on production and environmental conditions in a mesocosm system. Shrimp (14 g) and/or rabbitfish (19 g) were stocked in four treatments with different density but with the same total biomass (236 g m−2), including shrimp monoculture (SM) (17 shrimp m−2), shrimp–fish polyculture (SF) (11 shrimp and 4 rabbitfish m−2), fish–shrimp polyculture (FS) (6 shrimp and 8 rabbitfish m−2) and fish monoculture (FM) (12 rabbitfish m−2). After 10 weeks of experiment, shrimp survival and biomass were low in the treatments where shrimp were dominant (SM, SF), while rabbitfish survival and biomass were high in all the treatments. Shrimp mortality was assumed to be related to an excess of the system carrying capacity (CC). Results suggested that CC is linked to shrimp biomass/density rather than the system eutrophication level. The ecosystem became heterotrophic as daily feed supply was beyond 7 g m−2 per day. This threshold corresponded to the environmental CC of the semi-intensive shrimp culture system. Under these conditions, the combination of high fish biomass and low shrimp biomass appeared as the most valuable in terms of system performances.

International audience; Background: Most of the 29 Siganidae species are widely distributed through the Indo-Pacific area. In New Caledonia, these family was represented by 12 species. The present report is the first record of Siganus randalli in New Caledonian waters and provide information on its diet. Methods: Three specimens of Siganus randalli were caught in shallow mangrove waters of the southern part of New Caledonia. Their stomach contents and isotopic signatures (carbon and nitrogen) were analyzed and compared to others siganids species. Results and conclusion: This note provides the most southerly record of the rabbitfish Siganus randalli, which extends its distribution range by 1200 km southward and 1300 km southwest. The data on its diet, when compared with other co-occurring or more reef-associated siganid species, provide information on feeding processes and ecological functions associated with its mangrove habitat.

International audience; The functional formof spillover,measured as a gradient of abundance of fish,may provide insight about processes that control the spatial distribution of fish inside and outside theMPA. In this study,we aimed to infer on spillover mechanism of Diplodus spp. (family Sparidae) from a Mediterranean MPA (Carry-le-Rouet, France) from visual censuses and artisanal fisheries data. From the existing literature, three potential functional forms of spillover such as a linear gradient, an exponential gradient and a logistic gradient are defined. Each functional form is included in a spatial generalized linear mixed model allowing accounting for spatial autocorrelation of data. We select between the different forms of gradients by using a Bayesian model selection procedure. In a first step, the functional form of the spillover for visual census and artisanal fishing data is assessed separately. For both sets of data, ourmodel selection favoured the negative exponentialmodel, evidencing a decrease of the spatial abundance of fish vanishing around 1000 m from the MPA border. We combined both datasets in a joint model by including an observability parameter. This parameter captures how the different sources of data quantify the underlying spatial distribution of the harvested species. This enabled us to demonstrate that the different sampling methods do not affect the estimation of the underlying spatial distribution of Diplodus spp. inside and outside the MPA. We show that data from different sources can be pooled through spatial generalized linear mixedmodel. Our findings allow to better understand the underlying mechanisms that control spillover of fish from MPA.

International audience; We studied the trophic network architecture of the coral reef ecosystem of the New Caledonian lagoon. To encompass the main tropic levels, we assayed carbon and nitrogen stable isotopes in various organic matter sources, intermediate consumers (invertebrates and fish), and 19 species of predatory fish (total of 1229 samples). At each level, wide range of variations for δ13C and δ15N suggested multiple sources for the OM, and complex trophic relationships among the different organisms. Despite this complexity, four trophic structures were identified. 1) The predominant reef benthic food web (R-BFW) based on the OM produced by algal turf supplies most of intermediate consumers and all anguilliform fish studied. 2) The sedimentary benthic food web (S-BFW), and 3) the lagoon pelagic food web (L-PFW), respectively based on sedimentary OM (SOM) and particulate OM (POM) involve a wide range of organisms and represent complementary food webs for most anguilliform fish. 4) Finally, the detrital benthic food web (D-BFB) where the OM issued from seagrass is indirectly utilised by reef consumers plays a secondary role. Anguilliform fish are widespread sedentary predators that live in various habitats; the species sampled were respectively associated with the three main trophic structures identified, depending on their diet and habitat. This study reveals several major structures that are inter-connected to form an overall complex trophic network in the coral reefs.

International audience

Traditional stock assessment models were used to describe the current status of Lutjanus analis , L. chrysurus , L. jocu , L. synagris , and L. vivanus stocks off the coast of Northeast Brazil. The yield per recruit model, cohort analysis models (length-based cohort analysis (LCA), pseudo-cohort virtual population analysis (VPA), and real cohort VPA), and Thompson and Bell predictive model were used. The results showed LCA accumulates biases from pseudo-cohort VPA along with a high degree of sensitivity of growth parameters, whose determination is problematic and may not be adequate for many other reef species. Although the real cohort VPA based on short time series may also be limited, this method was determined to be the most appropriate within the traditional methods applied for the assessment of reef fish. However, the VPA model heavily depends on the accuracy of landing data and discards estimation and estimated natural mortality ( M ), so caution should be applied when using such models. The conservative fishing mortality index F 0.1 was found to be the most adapted index when the uncertainty of parameter estimation and model limitations were considered. Consequently, a drastic reduction of 80–90% of the current fishing effort is recommended. Despite the VPA and Thompson and Bell model limitations, these models can provide insight into species/fishery dynamics and can also be utilised to analyse the effects of changes in fishing level on catches. In addition, the trends presented in this study are confirmed in a companion paper using more complex models.

This study investigates the exploitation of Lutjanus analis, Lutjanus chrysurus, Lutjanus jocu and Lutjanus synagris from multiple gear types in Northeast Brazil using models allowing for technological interactions. The spatial distribution of species and fleets have played an important role in the Northeastern Brazilian artisanal fishery. The results of a predictive model by Thompson and Bell, along with a catch-at-age model, clearly showed that different fleets had distinct effects on snapper stocks. The fishery mortality ( F ) from small-scale fleets (‘Jangada’ and ‘Paquete’) was higher for coastal species such as L. synagris that are typically found in these areas . Conversely, L. jocu , that inhabits deeper waters, was most affected by motorised and sailing boats. Snappers were exploited differently at each of their life history stages. ‘Paquetes’ mainly exploited juveniles, whereas boats caught larger individuals farther from the coast. As a consequence, effort control through fleet regulation seems to be much more applicable in a tropical context than traditional catch control. Further modelling studies and management options relevant to the Northeast Brazil fishery are discussed.

Stable-isotope ratios (δ15N and δ13C) and diet of the red mullets Mullus barbatus and Mullus surmuletus were analysed in two zones differently subjected to the Rhone River runoff in the Gulf of Lions (north-west Mediterranean sea) in May and October 2004. δ15N and δ13C increased significantly with fish size in M. barbatus in both zones and seasons, whereas no significant trend was evidenced in M. surmuletus. A clear size-related shift in diet was observed in M. barbatus, with an increase in polychaete and shrimp consumption with size and a decrease in small crustacean consumption. In M. surmuletus, a diet shift was observed only between medium and large individuals. Large M. surmuletus preyed on shrimps, polychaetes, bivalves, ophiurids and amphipods, and ingested prey of lower mean mass than M. barbatus of similar size. Difference in size-related increase in δ15N between the two mullid fish species were related to difference of trophic level of their main prey. Sub-surface deposit-feeding polychaetes, carnivorous polychaetes, shrimps and brachyurans presented higher δ15N values than bivalves, small crustaceans and ophiurids. The lower δ13C values observed in M. barbatus compared to M. surmuletus were related to a higher consumption of sub-surface polychaetes in the former species. Significantly, lower δ13C were recorded in fishes collected off the Rhone River, particularly in spring, suggesting an influence of river inputs as a source of particular organic matter for mullids in this zone after the flooding season. Thus, these closely related sympatric fish species displayed diet divergences that were reflected in their stable isotopic signatures.

Much of the western Indian Ocean suffered widespread loss of live coral in 1998 and interest is now focussed on the indirect effects of this coral loss on other components of the ecosystem, in particular fishes. However, it is just as important to identify changes in fish assemblages at locations that did not suffer coral mortality to understand local versus regional drivers. We surveyed benthic and fish communities on a reef flat in Mauritius five times between 1994 and 2005. The design allowed for comparison through time, along the coast and between inshore and offshore reef locations. The benthic community demonstrates a clear trend along the coast, likely in response to a dredged water ski lane, but little change through time. Branching Acropora colonies dominate much of the live coral and best explain patterns in the fish assemblage (P < 0.01). Few changes in overall fish species richness through time were identified, and observed changes were within fishery target families rather than species reliant on live coral. Departure from expected levels of taxonomic distinctness suggests degradation in the community associated with the dredged ski lane. Non-metric multi-dimensional scaling of the fish assemblage demonstrates a similar pattern to that seen in the benthos; greater differences along the coast (Global R = 0.34) than through time (Global R = 0.17) and no trend between reef positions. SIMPER analysis identified two species of Stegastes as the main drivers of trends in the MDS plot and the most dominant of these, S. lividus, appears to be reducing species richness of the remaining fish community. The study highlights Mauritius as a regional refugia of thermally-sensitive corals and specialised fish, suggesting a need for careful management.

This work was part of a programme to assess the potential living resources within the Exclusive Economic Zone (EEZ) of Brazil that collected information on the catch composition and biology of the main species within the zone (REVIZEE). It aimed to identify and, using statistical tools, to assess the factors that influence the dynamics of the demersal fishery, targeting the rocky, coral reef and associated sandy seabeds of the continental shelf. Within the reef fishery of northeastern Brazil, snappers (family Lutjanidae), in particular Lutjanus chrysurus, L. synagris, L. analis, L. jocu, and, to a lesser extent, L. vivanus, are the main artisanal catch and contribute most to the similarity between groups. Among the factors considered, the spatial effect (geopolitical state as a factor) appeared to be the strongest attribute in isolating groups. Of the technological factors, trip duration better discriminated the catch composition than fleet category. However, given some exceptions mainly linked to favourable strong wind, trip duration categories were usually related to fleet dynamics, because motorized boats generally undertake longer trips. Such characteristics are important for management decisions, because fleets are likely to exploit different stages of the life cycle of a fish as well as different species while operating in different geographical areas. The catch analysis was characterized by a “lutjanid community” typical of rock, coral, and coral-sand habitats, and it is clear that this community is dominant in Brazil as well as in the more usually quoted regions such as the Bahamas, Antilles and along the coast from Yucatan to Panama.

We provide here the first information on the abundance, settlement patterns and microhabitat use of settlers of two Lessepsian siganid species, Siganus rivulatus and S. luridus, in comparison with the two main native herbivores, Sparisoma cretense (Scaridae) and Sarpa salpa (Sparidae). S. rivulatus was the most abundant species (72%), followed by S. cretense (20%) and S. luridus (8%), whereas S. salpa was rare (

The study was conducted to (1) estimate the effects of polyculture of blue shrimp Litopenaeus stylirostris with goldlined rabbitfish Siganus lineatus on production, environmental quality and water and sediment metabolism and (2) to determine if blue shrimp and goldlined rabbitfish polyculture is possible. The experiment was carried out for 12 weeks in a mesocosm system that consisted of 12 circular outdoor mesocosm fiberglass tanks (1.7 m2, 1275 L water volume). Shrimp (2.9 g) were randomly stocked at density of 15 shrimp.m− 2 without rabbitfish (control), with rabbitfish (25.5 g) at low density (1.2 fish.m− 2) (LDRB) and high density (2.4 fish.m− 2) (HDRB). Results indicated that goldlined rabbitfish S. lineatus did not affect shrimp growth performance. At the end of the experiment, the combined shrimp and rabbitfish yields in the LDRB (213 g.m− 2) treatment and the HDRB (295 g.m− 2) treatment were significantly greater (P < 0.05) than the shrimp yield in the control (143 g.m− 2). Most of the water and sediment parameters were similar among treatments. There was no significant difference (P > 0.05) in gross primary productivity and respiration between the HDRB treatment and the control. It was concluded that the polyculture of blue shrimp with goldlined rabbitfish is technically possible without degradation of the environment in the culture system.

International audience; The overexploitation of fishery resources has led to a major fisheries crisis. In this context, artisanal fisheries, and in particular small-scale coastal fisheries, appear as relevant alternatives for a sustainable use of coastal resources. Marine Protected Areas (MPA) are more and more used as management tools for these fisheries, as protection effects and targeted access regulations may benefit to commercial fishers. Managers and scientists need then quantitative information not only to adapt their management to the fishing activity present on their territory, but also to estimate the effects of MPA management on it. This study provides catch and effort estimates that are essential for appraising and managing the artisanal fishery in the Cote Bleue Marine Park (CBMP), a French Mediterranean MPA including two No-Take Zones of different age and size. A field protocol was defined and implemented between July 2009 and June 2010 within the CBMP. Seven m tiers were identified and characterized by target species, gear type, fishing grounds and fishing periods. During the one-year studied period, 3512 fishing trips and 4645 fishing operations were performed by 30 active boats in the Cote Bleue fishing territory, amounting to 9500 km of immersed nets. In total, approximately 130 tons of catch were landed in the six CBMP harbors, out of which 58% depend on the three main species caught on the Cote Bleue: hake (Merluccius merluccius), gilthead seabream (Sparus aurata) and common sole (Solea solea). The presented methodology could be part of a long term monitoring requiring close collaboration with local fishers. It enables adaptive management with respect to changes in fishing pressure (from inside and outside the MPA) that may impact the environment and its resources. (C) 2014 Elsevier B.V. All rights reserved.

The relationship between length of individual Stegastes nigricans and size of the territory that they defend, and both the spatial and temporal variation in territoriality were investigated monthly on a fringing coral reef of Reunion Island over the course of one year. Length of individual S. nigricans was correlated positively with size of the territory. Most small individuals were found separate from adults, in areas with low algal turf cover. This is probably due to strong intra-specific competition for access to algal food resources and shelter availability, and/or differences in habitat preference. Both abundance of individuals and surface defended showed seasonal fluctuations. Densities were slightly higher in austral summer than in winter, and the surface defended by individuals larger than 8 cm increased in winter. A permanent redistribution of territories also occured between individuals over time.

An unusual mass settlement event of the grouper Epinephelus merra occurred on the fringing coral reefs of Reunion Island (south-western Indian Ocean) in April 1994. This major event coincided with stormy conditions associated with the new moon period. The abundance of new settlers was surveyed for 45 days following settlement on both the reef flat and the back reef area of the coral reefs of St Gilles, La Saline and St Leu. Mean densities of settlers were higher on reef flats (maximum 474 ind/20 m2 at La Saline) than on back reef areas (maximum 156 ind/20 m2 at La Saline). Seven weeks later, densities of settled E. merra had drastically decreased, and did not differ with site and zone (18.5 ind/20 m2). Percentages of post-settlement mortality at that period ranged from 85 to 88% in back reef areas and from 93 to 95% on reef flats. A strong correlation between density of recruits and per capita mortality suggests density-dependent early post-settlement mortality for E. merra. The limitation of food resources and shelters, perhaps combined with an increase of diseases due to high population densities of settlers, was probably the main cause of mortality just after the mass settlement. Predation by reef fish, including cannibalism between settlers, is probably responsible for most subsequent mortality.

Copyright (c) 1997 Elsevier Science B.V. All rights reserved. The diet of the territorial damselfish Stegastes nigricans (Pomacentridae) was studied on a shallow coral reef flat of Reunion Island, S.W. Indian Ocean. Fishes were collected monthly from November 1989 to August 1990 in order to examine their stomach and gut contents. The temporal variability of the diet of S. nigricans was investigated on (1) a seasonal scale for the various size-classes and (2) a daily scale within two seasons. On average, algae accounted for 69.4% of the total weight of the stomach contents, all sizes combined. The total weight of all prey, and both the weight and the percentage of algae in stomach contents decreased in winter. This pattern was more pronounced for large (>8 cm total length) and medium (4-8 cm) than for small individuals (

International audience; Stable isotope ratios (d15N and d13C) and diet of three fish species, Stegastes nigricans, Chaetodon citrinellus and Epinephelus merra, were analyzed on the fringing coral reefs of two bays that are differentially exposed to river runoff on Moorea Island, French Polynesia. S. nigricans and C. citrinellus relied mostly on turf algae and presented similar trophic levels and d15N values, whereas E. merra fed on large invertebrates (crabs and shrimps) and had higher trophic levels and d15N values. Discrepancies existed between stomach content and stable isotope analyses for the relative importance of food items. Bayesian mixing models indicated that sedimented organic matter was also an important additional food for S. nigricans and C. citrinellus, and fishes for E. merra. The main sources of organic matter involved in the food webs ending with these species were algal turfs and surface sediments, while water particulate organic matter was barely used. Significant spatial differences in C and N isotopic ratios for sources and fishes were found within and between bays. Lower 13C and higher 15N values were observed for various compartments of the studied trophic network at the end of each bay than at the entrance. Differences were observed between bays, with organic sources and consumers being, on average, slightly more 13C-depleted and 15N-enriched in Cook's Bay than in Opunohu Bay, linked with a higher mean annual flow of the river at Cook's Bay. Our results suggest that rivers bring continental material into these two bays, which is partly incorporated into the food webs of fringing coral reefs at least close to river mouths. Thus, continental inputs can influence the transfer of organic matter within coral reef food webs depending on the diet of organisms.

This study investigates the effects of establishment of a marine reserve on the coral reef fish communities at Mayotte Island, Western Indian Ocean, after three years of protection. Both total species richness and global abundance did not differ significantly between protected and non-protected areas. Nevertheless, there were significant differences for numerous families and species. Most of the big carnivorous fishes (Serranidae, Lutjanidae, Lethrinidae) were more diverse and more abundant in the marine reserve. Conversely, other fishes, mainly in the families Pomacentridae, Scaridae and Acanthuridae, presented the opposite pattern. The mean biomass of commercial fish species was significantly higher in the reserve (202 g.m-2) than in non-protected areas (79 g.m-2). This pattern was also evident for carnivorous fishes, such as Epinephelus microdon, and semi-pelagic fishes, such as Caesionidae. In contrast, other commercial species, such as Scarus caudovittatus and Acanthurus nigricauda had highe...

Knowledge of fish life cycles is important for exploited species. In the Mediterranean Sea, catches of common sole (Solea solea) have fluctuated widely since the 1970s. Solea solea displays an ontogenetic shift in habitat: sole larvae are marine, juveniles inhabit shallow marine waters and coastal lagoons and adults inhabit deeper marine waters. Although the results of this study were obtained using only a small set of individuals, the otolith elemental composition and isotopic ratios were investigated for the three life stages (post-larval, juvenile and adult) in order to acquire a better knowledge of the variability in environmental conditions experienced by the common sole at each life stage in the NW Mediterranean. Moreover, this study provides the first evaluation of the potential of whole otolith microchemistry for investigating habitat connectivity in sole populations from the Gulf of Lions. The elemental and isotopic signatures of otoliths of post-larvae captured in various environments appear to show variations related to the River Rhône inputs (high Ba/Ca and low Sr/Ca ratios). Juveniles appear to show significant variations in otolith elemental and isotopic compositions depending not only on the physico-chemical properties of water in the nurseries they inhabit (Rhône River, Thau or Mauguio lagoons), but also as a result of variations in the chemical composition of their surrounding sediments and in their benthic prey. Adults exhibit otolith differences for isotopic ratios only, which is probably linked to the River Rhône inputs. Finally, several significant relationships were observed between otolith elemental composition and fish size in specimens captured at the River Rhône mouth. However, these variations seem to be an indication of the composition acquired in each environment rather than a sign of ontogeny. El conocimiento del ciclo de vida es importante para las especies comerciales de peces. En el mar Mediterráneo, las capturas de lenguado común (Solea solea) han fluctuado ampliamente desde la década de los 70. Solea solea presenta un cambio de hábitat ontogenético, las larvas son marinas, los juveniles viven en aguas marinas y en lagunas costeras, y los adultos viven en aguas marinas más profundas. Aunque los resultados de este estudio fueron obtenidos usando sólo un número pequeño de individuos, la composición de elemental los otolitos y las relaciones isotópicas fueron investigados en las tres etapas de vida (post-larval, juveniles y adultos) con el fin de adquirir un mejor conocimiento de la variabilidad en las condiciones ambientales que experimenta el lenguado común en cada etapa de la vida en el mediterráneo noroccidental. Por otra parte, este trabajo permite una primera evaluación del potencial de toda la microquímica de otolitos para la investigación de la conectividad del hábitat en las poblaciones de lenguado en el Golfo de León. Las señales elementales e isotópicos de los otolitos de las post-larvas capturadas en diferentes entornos muestran variaciones en relación a los materiales aportados por del río Ródano (alta relación Ba/Ca y baja relación Sr/Ca). Los juveniles parecen mostrar variaciones significativas en la composición elemental e isotópica de los otolitos dependiendo no sólo de las propiedades físico-químicas del agua en los viveros que habitan (Thau, Mauguio o el río Ródano), sino también como resultado de las variaciones en la composición química de los sedimentos circundantes y de su presa béntica. Los adultos presentan únicamente diferencias en las relaciones isotópicas de los otolitos, que está probablemente vinculado a por materiales aportados por el río Ródano. Por último, se observaron varias relaciones significativas entre la composición elemental de los otolitos y el tamaño de los peces en las muestras capturadas en la desembocadura del río Ródano. Sin embargo, estas variaciones parecen ser una indicación de la composición adquirida en cada entorno, más que ser debidas a la ontogenia.

International audience; Lionfish (Pterois volitans and P. miles) have become a major concern in the western Atlantic and Caribbean since their introduction in the 1980s. Invasive lionfish can reach very high population densities on coral reefs in their invaded range, yet there are few data from their native range in the Indo-Pacific for comparison. We compiled data on the geographical distribution and density of Indo-Pacific lionfishes in their native ranges from published and unpublished under - water visual censuses and field collections. We found that lionfish in their native Indo-Pacific range are unevenly distributed, with higher densities in the Indian Ocean than in the Pacific. Lionfish densities increase significantly with increasing latitude, and are significantly higher in continental areas than around islands. In the Indo-Pacific, lionfishes are found not only on reefs but also on soft bottoms and in nearshore habitats such as seagrass beds and mangroves, and near estuaries. Native lionfish can be found at depths greater than 75 m. Because lionfish can be cryptic and secretive, we estimate that only ~1/8 of Indo-Pacific lionfishes are detected during general underwater visual censuses. In the Pacific Ocean, the relative abundance of lionfish in the catch of reef-fish larvae is of the same order of magnitude as the relative abundance of adult lionfish within reef fish assemblages. Overall the observed densities of lionfishes in the Indo-Pacific are much lower (max. 26.3 fish ha-1) than the densities reported in their invaded Atlantic range (max. 400 fish ha-1). We found no effects of fishing or pollution on the densities of lionfishes.

International audience; The commercially important marine flatfish common sole (Solea solea) facultatively uses NW Mediterranean lagoons as nurseries. To assess the imprint left by the lagoonal passage, muscle carbon (C) and nitrogen (N) isotope values of S. solea juveniles caught in Mauguio lagoon in spring (shortly after arrival from the sea) and in autumn (before the return to the sea) were compared with values of juveniles from adjacent coastal marine nurseries. In addition, in the lagoon, sole otolith stable isotope (C and oxygen (0)) and elemental (11 elements) composition in spring and autumn, and the stable isotope composition (C and N) of organic matter sources in autumn, were determined. Overall, our data indicate that a distinct lagoonal signature existed. Specifically, lagoon soles showed a strong enrichment in muscle tissue N-15 (>6 parts per thousand) compared to their coastal relatives, likely linked to sewage inputs (see below), and a depletion in C-13 (1-2 parts per thousand), indicative of higher importance of C-13 depleted terrestrial POM in the lagoon compared to coastal nurseries. In addition, over the time spent in the lagoon, sole otolith delta C-13 and delta O-18 values and otolith elemental composition changed significantly. Analysis of the lagoon sole foodweb based on C and N isotopes placed sediment particulate organic matter (POM) at the base. Seagrasses, formerly common but in decline in Mauguio lagoon, played a minor role in the detritus cycle. The very strong N-15 enrichment of the entire foodweb (+7 to +11 parts per thousand) compared to little impacted lagoons and coastal areas testified of important human sewage inputs. Regarding the S. solea migration, the analysis of higher turnover and fast growth muscle tissue and metabolically inert and slower growth otoliths indicated that soles arrived at least several weeks prior to capture in spring, and that no migrations took place in summer. In the autumn, the high muscle delta N-15 value acquired in Mauguio lagoon would be a good marker of recent return to the sea, whereas altered otolith delta O-18 values and elemental ratios hold promise as long-term markers. The combination of several complementary tracers from muscle and otoliths may present the chance to distinguish between fish from specific lagoons and coastal nurseries in the future. (C) 2011 Elsevier Ltd. All rights reserved.

International audience; Splendid alfonsino Beryx splendens is a commercial species in several countries, but is not currently exploited in New Caledonia. Information on species biology and genetics can influence the development of fisheries and assist in their management, but the genetic structuring and diversity of B. splendens populations remain largely unknown. To improve knowledge of genetic parameters, we used mitochondrial DNA sequences to conduct a comparative study of populations from throughout the world. Fragments of 815 bp of cytochrome b gene were sequenced and used to interpret the species history. We analyzed 204 individuals representing 14 geographical populations worldwide. A special focus was put on populations from New Caledonia. Analysis of variation between sequences, based on pairwise F statistics and AMOVA, demonstrated a population subdivision between the Atlantic and Indo-Pacific Oceans (Fst = 0.11-0.32; P < 0.05). Minimum-spanning network analysis revealed a mainly star-shaped pattern, with two lineages that may represent population expansion following a bottleneck/founder event and/or suggest colonization by migratory events over large distances. Our observations demonstrated that the species seems to follow the oceanic currents. Analysis of the nucleotide sequences revealed 122 variable sites, which defined numerous haplotypes, some associated with particular geographical regions. These data suggest an extremely high intra-specific genetic diversity, even at small scales. Focusing on the New Caledonia area, statistical analysis did not reveal sub-structuring among samples, suggesting again that at least a fraction of individuals migrate. No significant isolation by distance pattern was observed in this species (R = -0.22; P = 0.79) among seamount populations in the EEZ.

We assessed spatial patterns in 37 PCB congeners, eight pesticides, and the heavy metals mercury and cadmium in the flatfish Solea solea at four sites in the Gulf of Lions (NW Mediterranean). Overall contaminant concentrations generally exceeded those reported for S. solea elsewhere, but fell into the range of other Gulf fishes, testifying of a relatively high contaminant load of this area. Spatial patterns in all three contaminant classes were highly significant, but differed among classes. PCB congener and chlorination class profiles also differed among sites. The observed patterns would be consistent with (1) PCB point-sources in the Eastern Gulf (Marseille, Rhone River) versus dominance of atmospheric input in the West, (2) pesticide input by the Rhone and from agricultural fields in the West, and (3) mercury point-sources near Marseille. The unique, site-specific contaminant profiles prove to be a powerful tool to differentiate between S. solea populations from different sites.

International audience; The relationships between total mercury (Hg) concentration and stable nitrogen isotope ratio (delta N-15) were evaluated in Mullus barbatus barbatus and M. surmuletus from the Mediterranean Sea and M. barbatus ponticus from the Black Sea. Mercury concentration in fish muscle was six times higher in the two Mediterranean species than in the Black Sea one for similar sized animals. A positive correlation between Hg concentration and delta N-15 occurred in all species. Increase in Hg concentration with delta N-15 was high and similar in the two Mediterranean fishes and much lower in the Black Sea species. Since this was neither related to trophic level difference between species nor to methylmercury (MeHg) concentration differences between the north-western Mediterranean and the Black Sea waters, we suggested that the higher primary production of the Black Sea induced a dilution of MeHg concentration at the base of the food webs. (c) 2009 Elsevier Ltd. All rights reserved.

Shape analyses were carried out on otoliths of the common sole, Solea solea (Linnaeus, 1758), in order to discriminate local populations in the North-Western Mediterranean Sea. Samples were collected in various environments like coastal lagoons, the outlet of the Rhone River as well as other marine sites. Morphological analyses highlighted a significant asymmetry between the left and right otoliths. This character could be acquired during or shortly after settlement on soft-bottoms when the individuals really become flatfishes. The otolith shape was described by seven harmonics from elliptic Fourier descriptors and by five indices of shape (coefficient of form, roundness, circularity, rectangularity, and ellipticity). The existence of several local populations of common sole in the NW Mediterranean was demonstrated. In particular, discriminant analyses highlighted significant differences in otolith shape according both to fish size and to the types of environment in which the fish live, i.e. coastal lagoons vs. marine sites, but also between sites belonging to the same type (lagoons, and marine sites). The differences in shape could be linked (1) to the particular environmental conditions of each site, and (2) to changes in metabolic and/or physiological conditions according to the stage of development of the fish which most likely influences the otolith growth.

A total of 212 carnivorous coastal fish species from New Caledonia, represented by 7335 individuals, were analysed for their diet. Fifty two prey items were identified and later grouped into broader taxonomic categories refered as “prey types”. For each fish species 6 biological traits were defined: maximum adult size, major biotope, schooling behaviour, home range, nycthemeral behaviour, degree of crypticity. A general linear model was fit to the diet data taking into account these traits, and depth of capture and fish family. This model was applied to the average number of prey types/stomach and to the volume of 5 prey types: nekton, crustaceans, molluscs, echinoderms, worms. A second analysis was performed on the effect of observed size on diet composition, taking into account these traits and taxonomy. This analysis was restricted to species with at least five individuals, representing 113 species from 33 families. More detailed information is given for the three major families, Serranidae, Lutjanidae and Lethrinidae and intra-family variations are illustrated for Lethrinidae. All the factors tested had significant effects on diet, fish size and taxonomy being the two major factors. The five prey types analysed in detail displayed marked differences according to the factors studied. In particular nekton increased in importance with fish size, whereas crustaceans decreased and molluscs presented a dome shaped relationship. Nekton and crustaceans made the bulk of the diet of most species, with molluscs being at times important. Echinoderms and worms were never a major food item and were eaten only by a restricted range of species.

The humphead wrasse, Cheilinus undulatus, is the largest living member of the family Labridae, with a maximum size exceeding 2 m and 190 kg. Its geographic range covers much of the Indo-Pacific. The species is not common, recorded maximum adult densities rarely exceeding 20 fish/10,000 m2. Small individuals are typically associated with high coral cover; larger fish are found mainly on outer or deep reefs, steep slopes and passes, singly or in small groups and seagrasses. However, for reproduction the species forms small spawning aggregations of tens to more than one hundred fish. The diet of the humphead wrasse includes large invertebrates and small fishes. The species attains at least 30 years and reaches sexual maturation at about 35–50 cm total length and

International audience; Quantifying the scale and importance of individual dispersion between populations and life stages is a key challenge in marine ecology. The common sole (Solea solea), an important commercial flatfish in the North Sea, Atlantic Ocean and the Mediterranean Sea, has a marine pelagic larval stage, a benthic juvenile stage in coastal nurseries (lagoons, estuaries or shallow marine areas) and a benthic adult stage in deeper marine waters on the continental shelf. To date, the ecological connectivity among these life stages has been little assessed in the Mediterranean. Here, such an assessment is provided for the first time for the Gulf of Lions, NW Mediterranean, based on a dataset on otolith microchemistry and stable isotopic composition as indicators of the water masses inhabited by individual fish. Specifically, otolith Ba/Ca and Sr/Ca profiles, and d13C and d18O values of adults collected in four areas of the Gulf of Lions were compared with those of young-of-the-year collected in different coastal nurseries. Results showed that a high proportion of adults (.46%) were influenced by river inputs during their larval stage. Furthermore Sr/Ca ratios and the otolith length at one year of age revealed that most adults (,70%) spent their juvenile stage in nurseries with high salinity, whereas the remainder used brackish environments. In total, data were consistent with the use of six nursery types, three with high salinity (marine areas and two types of highly saline lagoons) and three brackish (coastal areas near river mouths, and two types of brackish environments), all of which contributed to the replenishment of adult populations. These finding implicated panmixia in sole population in the Gulf of Lions and claimed for a habitat integrated management of fisheries.

The fish assemblages of two shallow soft-bottom areas located in the Gulf of Fos (NW Mediterranean) were studied by means of 57 trawl surveys carried out on both seasonal and diel scales between 1983 and 1985. A total of 47 fish species was recorded, with a mean density and biomass of 650 individuals ha(-1) and 2.67 kg ha(-1), respectively. Most of the fluctuations observed were on the spatial scale. Strong differences in fish assemblages were observed between the two areas, with both higher species richness and biomass in the outer part of the gulf (La Gracieuse), while a higher density of individuals characterised its inner part (Bay of Carteau). This spatial pattern was due to a small number of species, such as the gobiids Gobius niger and Pomatoschitus minutus in Carteau, and the flatfish Arnoglossus laterna, Buglossidium luteum and Salen solea in La Gracieuse. These differences were probably induced by differences in the hydrological and benthic characteristics of the two study areas. Decreases in species richness, density and/or biomass were observed in both areas over the study period, although this trend was not significant in all cases. These decreases may have been linked to interannual variations in the mean flow rate of the Rhone River (-28.1% between 1983 and 1985), which might have induced a decrease in the density of benthic invertebrate populations. We suggest that a similar reaction occurred in fish populations, as most of them are known to feed on these invertebrates. Diel patterns did not reveal any significant trends. However, an increase in density and biomass at sunset, and a decrease before sunrise were observed in summer in both areas, and the presence of certain specific species was recorded in catches at determined hours of the diel cycle. These observations were likely due to the activity cycles (diurnal vs. nocturnal) of the fish species. (, Les communautés de poissons des fonds meubles de deux secteurs du golfe de Fos ont été étudiées par 57 chalutages, réalisés en différentes saisons et à différentes heures du nycthémère, entre 1983 et 1985. Un total de 47 espèces de poissons a été recensé, avec une densité et une biomasse moyennes de 650 individus ha–1 et 2,67 kg ha–1, respectivement. L’essentiel des différences observées est lié à la distribution spatiale des espèces, avec une forte distinction entre les deux secteurs: la richesse spécifique et la biomasse ont été plus fortes à l’extérieur du golfe (La Gracieuse), alors que la densité a été plus forte à l’intérieur (baie de Carteau). Cette ségrégation est surtout due à un petit nombre d’espèces, comme les Gobiidae Gobius niger et Pomatoschitus minutus, surtout capturés à Carteau, et les poissons plats Arnoglossus laterna, Buglossidium luteum et Solea solea à La Gracieuse. Ces différences sont probablement liées aux caractéristiques hydrologiques et benthiques de ces secteurs. Au cours de la période d’étude, la richesse spécifique, la densité et/ou la biomasse ont diminué sur les deux secteurs. Les variations interannuelles du débit du Rhône (–28,1% entre 1983 et 1985) peuvent avoir induit une diminution de la densité des populations d’invertébrés benthiques. Cela aurait eu des conséquences semblables sur les poissons car la plupart d’entre eux se nourrissent de ces invertébrés. Aucune tendance particulière n’est clairement apparue au cours du nycthémère. Cependant, la densité et la biomasse ont augmenté durant la saison estivale et sur les deux secteurs, au moment du crépuscule, et ont diminué à l’aube. De plus, certaines espèces ont été capturées préférentiellement à des heures bien déterminées du nycthémère. Ces observations sont à relier aux rythmes d’activités (diurnes vs. nocturnes) des poissons qui habitent ces petits fonds sableux.

Fish from lagoon and reef in New Caledonia are mainly caught by artisanal fisheries and subsistence fishing. The present study aimed at estimating these fish standing stocks, at finding the main factors influencing the spatial distribution of these fish, and at estimating the maximum sustainable yield with considerations for socio-economic aspects sensu late. A total of 1406 stations was surveyed in the Northern Province of New Caledonia. Sampling was stratified according to three zones (north, east and west) and three biotopes (coral reefs, near-reef areas and lagoon bottoms). This work demonstrates the existence of important fish stocks of commercial interest in reefal and lagoonal waters of the Northern Province, estimated at about 138 300 t. The standing stocks, which may be considered as non-exploited in the north zone, were mainly composed by large individuals belonging to slow-growing species ('K' strategy). The current catches of fish are globally very low, approximatively 10-times less than the pressure which would achieve a maximum sustainable yield. The characteristics of the local market for fish in New Caledonia, mainly in the Northern Province,:indicate that fish consumption directly reflects fishing pressure. Indeed, subsistence fishing (25.7 kg of fish per inhabitant and per year) represents 92 % of the total fishing pressure, thus the commercial fishing activities may be considered as a minor component. So, it seems that the demography and local feeding habits will probably be the most important factors which will determine the future variations of artisanal fishing activities and status of standing stocks in the northern Province of New Caledonia. (, Les poissons lagonaires et récifaux de Nouvelle-Calédonie sont capturés principalement par les pêcheries artisanales et par la pêche de subsistance. Cet article vise à estimer les stocks de ces poissons, à déterminer les facteurs qui influencent leur distribution dans l'espace, et à évaluer le stock exploitable sans danger pour la ressource, en fonction de critères socio-économiques sensu lato. Un total de 1 406 stations a été étudié en Province Nord de la Nouvelle-Calédonie. L’échantillonnage a été stratifié en fonction de trois zones (nord, est et ouest) et de trois biotopes (récifs coralliens, abords récifaux et fonds de lagon). Nous avons mis en évidence l'existence d'importants stocks de poissons d'intérêt commercial dans les zones récifo-lagonaires de la Province Nord, estimés à 138 300 t. Les stocks, quasiment inexploités dans la zone nord, sont majoritairement composés par des individus de tailles élevées, appartenant à des espèces à croissance lente (stratégie « K »). Les captures actuelles de poissons sont faibles et demeurent dix fois inférieures à celles qui permettraient d'exploiter le stock sans danger pour la ressource. Les caractéristiques locales en Province Nord montrent que la consommation de poisson par les populations côtières reflète assez précisément la pression de pêche. Celle-ci est, en effet, largement liée à la pêche d'autoconsommation (25,7 kg de poisson par habitant et par an, soit 92 % de la pêche totale), alors que la pêche commerciale reste mineure. Il semble donc que se soient la démographie et les habitudes alimentaires qui seront, dans l'avenir, les facteurs déterminants des variations des activités des pêcheries artisanales et de l’état des stocks en Province Nord de la Nouvelle-Calédonie.

The potential yields of demersal reefal and lagoonal finfish, which are valuable for trade or consumption in the Northern Province of New Caledonia, are unknown. Fishing pressure was estimated from tally-sheets of professional fishermen to assess trade fishing and a household consumption survey to assess subsistence fishing. Total yield was estimated to be 1 326 tonnes in 1995, 94 % of which correspond to subsistence fishing. Most of the catches were taken from the east and west coasts; in the north zone (Belep Archipelago) catches were very low. From this fishing pressure and the total stock values, the maximum sustainable yield (MSY) was estimated to be 12 600 t, which was about 10 % of the total stocks assessed in the Northern Province (138 300 t). This MSY was dominated by five families, namely Lethrinidae, Acanthuridae, Scaridae, Serranidae and Lutjanidae. The results suggest that fishing effort in the Northern Province of New Caledonia could increase without endangering the stock. However, on a smaller geographical scale, some locations (Kone and Nepoui on the west coast), reef habitats (near-reef areas) or species groups (fish caught by line) were already being intensively fished. Fishing techniques should be diversified so that part of the fishing effort be redirected toward the least heavily exploited groups of species and biotopes. (C) 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS., Cette étude évalue le potentiel d’exploitation des poissons démersaux récifo-lagonaires d’intérêt commercial dans les lagons de la Province Nord de la Nouvelle-Calédonie. La pression de pêche est estimée d’après les relevés des pêcheurs professionnels et le budget de consommation des ménages. Les captures totales ont été estimées à 1 326 tonnes en 1995, dont 94 % sont représentés par la pêche de poissons consommés sur place. Les captures sont effectuées sur les côtes ouest et est, et sont très faibles dans le lagon nord (Bélep). Compte tenu de cette pression de pêche d’une part, et des stocks d’autre part, la prise maximale soutenue annuelle a été estimée à 12 600 t, soit environ 10 % du stock total (138 300 t). Elle est principalement constituée par des espèces de cinq familles : les Lethrinidés, Acanthuridés, Scaridés, Serranidés et Lutjanidés. Comparés à la pression de pêche sur l’ensemble des lagons, les stocks semblent loin d’être menacés dans leur ensemble. Il serait donc possible d’augmenter sensiblement l’effort de pêche. Cependant, à une échelle géographique plus fine, certains secteurs communaux (Koné et Népoui sur la côte ouest), certains biotopes récifaux (les abords récifaux), ou certains groupes d’espèces (poissons de ligne) semblent supporter déjà une activité conséquente. Des recommandations sont formulées, notamment la mise en place d’un suivi de la ressource des espèces cibles et la réorientation de l’effort de pêche en direction d’autres groupes d’espèces et d’autres biotopes grâce à une diversification des techniques de captures.

Lagoon fish in New Caledonia are mainly caught by artisanal fisheries and subsistence fishing. Reef fish are the major component of this catch. The present study aimed at estimating these reef fish standing stocks and at finding the main factors influencing the distribution of these fish. Sampling of 904 stations was stratified according to three zones (north, east and west) and three reef types (barrier, intermediate and fringing). Fish communities exhibited strong heterogeneity in their distribution, showing higher biomass (maximum of 447 g.m(-2)) and total standing stock (43 000 tonnes) in the north zone than in the east and west zones. Similarly, observed patterns were dependent on reef types: higher biomass and total standing stock being observed on barrier reefs than on intermediate or fringing reefs. The total standing stocks, which were about 65 000 t, were mainly composed of herbivorous fish families such as the Acanthuridae and Scaridae. The differences in the patterns of distribution of species, individuals and standing stocks between reef types may be explained by variations in terrestrial influences and reef morphology, whereas differences among zones were most likely due to accessibility of fishing areas and fishing pressure. The latter is almost non-existent in the north zone, which can thus be considered to be almost unexploited commercially. This most likely explains the high proportion, 77 %, of long-lived species in the biomass of this zone. The results might have implications in management of reefs elsewhere in the South Pacific, for which similar data are only scarcely available. (C) 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS., Les poissons de lagon de Nouvelle-Calédonie sont exploités par les pêcheries artisanales, dont les poissons de récifs constituent la majeure partie de ces captures. Ce travail vise à estimer les stocks de ces poissons récifaux et à déterminer les principaux facteurs qui influencent leur distribution. L’échantillonnage de 904 stations a été stratifié en fonction de trois zones (nord, est et ouest) et de trois types de récif (barrière, intermédiaire et frangeant). Les peuplements de poissons ont montré une très forte hétérogénéité dans leur répartition de la biomasse et des stocks. Dans la zone nord, ces valeurs ont été bien supérieures (jusqu’à 447 g·m–2, et stocks de 43 000 tonnes) à celles des zones est et ouest. La distribution de ces peuplements est également fonction du biotope considéré, de plus fortes densités et biomasses étant relevées sur les récifs barrières, par contraste avec les récifs intermédiaires et frangeants. La majeure partie du stock total, qui est de l’ordre de 65 000 t, est constituée d’espèces herbivores d’Acanthuridés et de Scaridés. Les principales causes des différences observés dans la répartition des espèces et des individus, ainsi que des stocks entre types récifaux seraient liées à des différences d’apports terrigènes et de morphologie récifale, tandis que les différences relevées entre les trois zones sont davantage liées à l’accessibilité des ressources et à la pression de pêche. Cette dernière est très faible dans la zone nord, qui peut être considérée comme inexploitée. Cela expliquerait la forte proportion, 77 %, des espèces à longue espérance de vie de la biomasse totale de cette zone. La gestion des pêcheries artisanales dans l’ensemble du Pacifique Sud, où les données sont rarement disponibles, implique la prise en compte de ces observations

A comparative study was conducted in two zones of the Northern Province of New Caledonia, one located windward (east coast) and the other located leeward (west coast). In each zone, three major sectors were investigated: fringing reefs close to areas of important mining activities, fringing reefs close to areas of moderate mining activities, and fringing reefs close to areas free of mining activities. In addition, on the west coast, fringing reefs close to areas of high natural ground erosion were also studied. Only commercial fish species sensus late were censused on a total of 163 stations, concerning 165 fish species. Substrate characteristics were not different between zones and sectors. However, significant differences were observed for living organisms: live coral cover was higher in non-mining sectors than in mining ones, and algal cover increased with increasing mining activities. The three main descriptors of the commercial fish communities (e.g. mean species richness, density and biomass) have all shown lower values in sectors submitted to the lowest ground erosion levels, although these trends were not all statistically significant. Similar results were found for some of the major fish families, such as the Acanthuridae and Siganidae, whereas other families had no specific pattern, such as the Lut-janidae, or a 'partial' pattern (i.e. on only one coast), such as the Serranidae, Lethrinidae, Mullidae, Labridae and Scaridae., Une étude comparative a été réalisée pour évaluer les effets des apports terrigènes sur les peuplements de poissons d'intérêt commercial de la province Nord de la Nouvelle-Calédonie. Deux zones sont étudiées, l'une localisée au vent (côte est) et l'autre sous le vent (côte ouest). Dans chaque zone, trois régions principales sont distinguées : récifs frangeants proches de secteurs soumis à d'importantes activités minières, récifs frangeants proches de secteurs soumis à des activités minières modérées, et récifs frangeants proches de secteurs non miniers. De plus, sur la côte ouest, des récifs frangeants proches de secteurs soumis à une forte érosion terrigène naturelle sont également étudiés. Seules les espèces de poissons d'intérêt commercial au sens large ont été recensées (165 espèces) sur un total de 163 stations. Les caractéristiques du substrat ne différent pas d'une zone à l'autre, ni d'une région à l'autre. En revanche, des différences significatives sont observées pour les organismes recouvrants : la couverture en corail vivant est plus forte sur les récifs proches de secteurs non miniers, alors que la tendance est inverse pour le recouvrement algal. Les trois descripteurs principaux des communautés de poissons commerciaux (richesse spécifique, densité et biomasse) sont plus faibles dans les secteurs non miniers, bien que cette tendance ne soit pas toujours statistiquement significative. Des résultats similaires sont obtenus pour certaines des principales familles de poissons, comme les Acanthuridae et les Siganidae, tandis que d'autres familles ne montrent aucune tendance particulière, comme les Lutjanidae, ou une tendance « partielle å (c'est-à-dire sur une seule des deux côtes), comme les Serranidae, les Lethrinidae, les Mullidae, les Labridae et les Scaridae

The spatial distribution of commercial reef fishes from four areas of the northern lagoon of New Caledonia was studied following a terrestrial runoff gradient ranging from very low on the western barrier reef to high on the northern fringing reefs. Species richness decreased from eastern reefs (30.4 species transect-1) to northern fringing reefs (21.4), suggesting a link between terrestrial influence and species richness. Density ranged from 0.49 fish m-2 (western reefs) to 0.69 fish m-2 (eastern reefs), but did not show any particular trend. Biomasses increased from 148 g m-2 on the northern fringing reefs to 447 g m-2 on the western reefs. Such high values are likely due to the very low fishing pressure in the whole area. Numerous significant relationships were found between fish descriptors (i.e. diversity, density, biomass and mean weight) and terrestrial influences (i.e. distance to coast, visibility, % of carbonates in the sediment, % of mud, granulometry and color of sediments). Descriptors of total ichthyofauna were all positively correlated with decreasing terrestrial influence. The 6 dominant fish families displayed similar trends and were positively correlated with decreasing terrestrial influence, except for Siganidae which showed the opposite trend. Some of the most common species, such as Scarus sordidus and Siganus doliatus, had no particular distribution pattern. Size, density and biomass of other species, such as Lethrinus atkinsoni, Cheilinus undulatus, Hipposcarus longiceps, Scarus microrhinos and Acanthurus xanthopterus, were significantly correlated to parameters characteristic of offshore reefs. Conversely, Plectropomus leopardus, Scarus ghobban and Siganus lineatus were closely related to coastal reefs. Some species had significant correlations with parameters characteristic of intermediate reefs, such as Scarus schlegeli and Acanthurus nigricauda. Data for Plectropomus leopardus and Scarus ghobban suggested a possible ontogenic migration of these two species from the northern fringing reefs, where numerous small individuals were observed, to offshore barrier reefs, where only large individuals were recorded.

A comparative study of the size distribution of four fish species was performed on three geomorphological zones (back reef, inner reef flat and outer reef flat) on two comparable fringing reef areas (disturbed and non-disturbed) of Reunion Island, S.W. Indian Ocean. The species chosen Chaetodon trifasciatus, Dascyllus aruanus, Stethojulis albovittata and Ctenochaetus striatus were selected both for their abundance and their diverse diets. The method used is based on the estimation of fish size directly underwater by comparison to a graduated table, i.e. photographs of the species for which different size-classes were previously determined. For the two areas, the size of fishes increases from the back reef zone to the outer reef flat, except for D. aruanus which is not present in sufficient numbers on the outer reef flat to allow a statistical analysis. This suggests the existence of a nursery zone in the back reef from which these species might colonize the reef flat. On the back reef zone and the inner reef flat, there is a significant difference in the size distribution of fishes between the disturbed and non-disturbed areas, except for S. albovittata. The number of juveniles is significantly lower in the disturbed area, probably due to environmental perturbations.