Éditeur(s) : HAL CCSD
Résumé : International audience
ISSN: 1937-7835

hal-01391676
https://hal-univ-perp.archives-ouvertes.fr/hal-01391676

Éditeur(s) : HAL CCSD
Résumé : National audience
The Lesser Antilles subduction zone has produced no recent strong thrust earthquakes, making it difficult to quantify the seismic hazard from such events. The Lesser Antilles arc has a low subduction rate and an accretionary wedge that is very wide at its southern end. To investigate the effect of the wedge on seismogenesis, numerical models of forearc thermal structure were constructed along six transects perpendicular to the arc in order to determine the thermally predicted width of the seismogenic zone. The geometry of each section is constrained by published seismic profiles and crustal models derived from gravity and seismic data and by earthquake hypocenters at depth. A major constraint on the deep part of the model is that mantle temperature beneath the volcanic arc should achieve a temperature of 1,100°C to generate partial melts. Predicted surface heat flow is compared to the available heat flow observations. Thermal modeling results indicate a systematic southward increase in the width of the seismogenic zone, more than doubling in width from north to south and corresponding to a dramatic southward increase in forearc width (distance from the arc to the deformation front of the accretionary wedge). The minimum width of the seismogenic zone (distance between the intersections of the subduction interface with the 150°C and 350°C isotherms) increases from about 80 km, north of 16°N, to 230 km, at 13°N. The maximum width (between the 100°C and 450°C isotherms) ranges from about 150 km in the north to up to 320 km in the south. This large variation in the width of the seismogenic zone is a consequence of the increasing width of the accretionary wedge to the south, caused by the increased thickness of sediment on the subducting plate. There is good agreement between the thermally predicted seismogenic limits and the sparse distribution of recorded thrust earthquakes, which are observed only in the northern portion of the arc. Possible scenarios for mega-thrust earthquakes are discussed. Depending on the segment length (along-strike) of the rupture plane, the occurrence of an event of magnitude 8-9 cannot be excluded.
Bulletin Société Géologique de France

insu-00814056
https://hal-insu.archives-ouvertes.fr/insu-00814056
DOI : 10.2113/gssgfbull.184.1-2.47

Éditeur(s) : HAL CCSD
Résumé : International audience
Kisspeptins are well known as mediators of the coordinated communication between the brain-pituitary axis and the gonads in many vertebrates. To test the hypothesis that gonadal steroids regulate kiss1 and kiss2 mRNA expression in European sea bass (a teleost fish), we examined the brains of gonad-intact (control) and castrated animals, as well as castrated males (GDX) and ovariectomized females (OVX) that received testosterone (T) and estradiol (E2) replacement, respectively, during recrudescence. In GDX males, low expression of kiss1 mRNA is observed by in situ hybridization in the caudal hypothalamus (CH) and the mediobasal hypothalamus (MBH), although hypothalamic changes in kiss1 mRNA levels were not statistically different among the groups, as revealed by real-Time PCR. However, T strongly decreased kiss2 expression levels in the hypothalamus, which was documented in the MBH and the nucleus of the lateral recess (NRLd) in GDX T-Treated sea bass males. Conversely, it appears that E2 evokes lowkiss1mRNAin the CH, while there were cells expressing kiss2 in the MBH and NRLd in these OVX females. These results demonstrate that kisspeptin neurons are presumably sensitive to the feedback actions of sex steroids in the sea bass, suggesting that the MBH represents a major site for sex steroid actions on kisspeptins in this species. Also, recent data provide evidence that both positive and negative actions occur in key factors involved in sea bass reproductive function, including changes in the expression of gnrh-1/gonadotropin, cyp19b, er and ar genes and sex steroid and gonadotropin plasma levels in this teleost fish. © 2016. Published by The Company of Biologists Ltd.
Journal of Experimental Biology

hal-01406072
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01406072
DOI : 10.1242/jeb.137364
PUBMED : 27591305

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The life-history traits and population dynamics of species are increasingly being attributed to the characteristics of their preferred habitats. While coral reef fish are often strongly associated with particular habitats, long-term studies establishing the demographic and life-history consequences of occupying different reef substrata are rare and no studies have monitored individuals in situ over their lifetime and determined the fate of their offspring. Here, we documented a quasi-turnover and local reproductive success for an entire population of orange clownfish (Amphiprion percula) from Kimbe Island, Papua New Guinea, by taking bi-annual samples of DNA over a 10-yr period (2003–2013). We compared demographic and life-history traits of individuals living on two host anemone species, Heteractis magnifica and Stichodactyla gigantea, including female size, adult continued presence (a proxy for relative longevity range), early post-settlement growth, the number of eggs per clutch and ‘local’ reproductive success (defined for each adult as the number of offspring returning to the natal population). Our results indicate that while the relative longevity of adults was similar on both host anemone species, females living in H. magnifica were larger than females in S. gigantea. However, despite females growing larger and producing more eggs on H. magnifica, we found that local reproductive success was significantly higher for clownfish living in S. gigantea. Life-history traits also exhibited local spatial variation, with higher local reproductive success recorded for adults living on S. gigantea on the eastern side of the island. Our findings support a ‘silver-spoon’ hypothesis that predicts individuals that are fortunate enough to recruit into good habitat and location will be rewarded with higher long-term reproductive success and will make a disproportionate contribution to population renewal.
ISSN: 0722-4028

hal-01357939
https://hal-univ-perp.archives-ouvertes.fr/hal-01357939
DOI : 10.1007/s00338-016-1485-1

Éditeur(s) : HAL CCSD CSIRO Publishing
Résumé : International audience
The present study assessed the occurrence of multiple paternity in four litters of bull shark Carcharhinus leucas (n¼5, 8, 9 and 11 embryos) sampled at Reunion Island in the Western Indian Ocean. Using 21 microsatellite loci, we revealed that two litters were generated from two sires each, demonstrating for the first time multiple paternity for this species. We also reported a high paternal skew (10 : 1 in Litter 1 and 7 : 1 in Litter 3), which may be because of postcopulatory or post-zygotic selection processes. These results contribute to a better understanding of the reproductive behaviour of the bull shark, which remains poorly documented. The present study must be expanded to assess the frequency of multiple paternity in this species, and to test for genetic or cryptic benefits (convenience polyandry), which is important for long-term conservation and management plans.
ISSN: 1323-1650

hal-01253775
https://hal.archives-ouvertes.fr/hal-01253775
https://hal.archives-ouvertes.fr/hal-01253775/document
https://hal.archives-ouvertes.fr/hal-01253775/file/Pirog%20et%20al.%20-%202015%20-%20First%20evidence%20of%20multiple%20paternity%20in%20the%20bull%20s_hal.pdf
DOI : 10.1071/mf15255

Éditeur(s) : HAL CCSD Wiley Open Access
Résumé : International audience
Coral disease outbreaks have increased over the last three decades, but their causal agents remain mostly unclear (e.g., bacteria, viruses, fungi, protists). This study details a 14-month-long survey of coral colonies in which observations of the development of disease was observed in nearly half of the sampled colonies. A bimonthly qPCR method was used to quantitatively and qualitatively evaluate Symbiodinium assemblages of tagged colonies, and to detect the presence of Vibrio spp. Firstly, our data showed that predisposition to disease development in general, and, more specifically, infection by Vibrio spp. in Acropora cytherea depended on which clades of Symbiodinium were harbored. In both cases, harboring clade D rather than A was beneficial to the coral host. Secondly, the detection of Vibrio spp. in only colonies that developed disease strongly suggests opportunistic traits of the bacteria. Finally, even if sporadic cases of switching and probably shuffling were observed, this long-term survey does not suggest specific-clade recruitment in response to stressors. Altogether, our results demonstrate that the fitness of the coral holobiont depends on its initial consortium of Symbiodinium, which is distinct among colonies, rather than a temporary adaptation achieved through acquiring different Symbiodinium clades.
ISSN: 2045-7758

hal-01270779
https://hal-univ-perp.archives-ouvertes.fr/hal-01270779
https://hal-univ-perp.archives-ouvertes.fr/hal-01270779/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01270779/file/41080.pdf
DOI : 10.1002/ece3.1895

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Determining the conditions under which populations may persist requires accurate estimates of demographic parameters, including immigration, local reproductive success, and mortality rates. In marine populations, empirical estimates of these parameters are rare, due at least in part to the pelagic dispersal stage common to most marine organisms. Here, we evaluate population persistence and turnover for a population of orange clownfish, Amphiprion percula, at Kimbe Island in Papua New Guinea. All fish in the population were sampled and genotyped on five occasions at 2-year intervals spanning eight years. The genetic data enabled estimates of reproductive success retained in the same population (reproductive success to self-recruitment), reproductive success exported to other subpopulations (reproductive success to local connectivity), and immigration and mortality rates of sub-adults and adults. Approximately 50% of the recruits were assigned to parents from the Kimbe Island population and this was stable through the sampling period. Stability in the proportion of local and immigrant settlers is likely due to: low annual mortality rates and stable egg production rates, and the short larval stages and sensory capacities of reef fish larvae. Biannual mortality rates ranged from 0.09 to 0.55 and varied significantly spatially. We used these data to parametrize a model that estimated the probability of the Kimbe Island population persisting in the absence of immigration. The Kimbe Island population was found to persist without significant immigration. Model results suggest the island population persists because the largest of the subpopulations are maintained due to having low mortality and high self-recruitment rates. Our results enable managers to appropriately target and scale actions to maximize persistence likelihood as disturbance frequencies increase.
ISSN: 0962-8452

hal-01239322
https://hal-univ-perp.archives-ouvertes.fr/hal-01239322
DOI : 10.1098/rspb.2015.1311

Éditeur(s) : HAL CCSD Consejo Superior de Investigaciones Científicas
Résumé : International audience
The temporal variation in carbon and nitrogen isotopic compositions (noted as δ 13 C and δ 15 N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period of 24 days, juveniles were reared in aquaria and subjected to two different feeding treatments: granules or algae. The dynamics of δ 13 C and δ 15 N in two muscles (the adductor mandibulae complex and the epaxial musculature) having different functions were compared. At the end of experiments, a steady-state isotopic system in each muscle tissue was not reached. Especially for the algal treatment, we found different patterns of variation in isotopic compositions over time between the two muscles. The turnovers of δ 13 C showed opposite trends for each muscle but differences are mitigated by starvation and by the metamorphosis. Our study highlighted that the metabolism of coral reef fish may be subjected to catabolism or anabolism of non-protein precursors at settlement, inducing variation in isotopic compositions that are not linked to diet change. Comparación de la dinámica de variación isotópica en dos músculos de un pez de arrecife de coral durante la fase de asentamiento Resumen: La variación temporal en la composiciones isotópicas del carbono y nitrógeno (δ 13 C y δ 15 N) fue investigada en el pez cirujano Acanthurus triostegus en Moorea (Polinesia Francesa). Durante un período de 24 días, peces juveniles se mantuvieron en acuarios y se sometieron a dos tratamientos de alimentación: gránulos o algas. Se compararon las dinámicas de cambio δ 13 C y δ 15 N en dos músculos con diferentes funciones (complejo aductor mandibular y musculatura epiaxial). Al final de los experimentos, no se alcanzó un sistema isotópico de estado estacionario en ningún tejido. Especialmente para el tratamiento de algas, encontramos distintos patrones de variación en composiciones isotópicas en el tiempo entre los dos músculos. Las variaciones en δ 13 C mostraron tendencias opuestas para cada músculo, pero las diferencias fueron mitigadas por la inanición y la metamorfosis. Nuestro estudio destaca que el metabolismo de los peces de arrecife puede ser sometido a catabolismo o anabolismo por los precursores no proteicos durante el asentamiento, induciendo variación en las composi-ciones isotópicas que no están vinculados al cambio de dieta.
ISSN: 0214-8358

Droits : http://creativecommons.org/licenses/by-nc/
hal-01212253
https://hal-univ-perp.archives-ouvertes.fr/hal-01212253
https://hal-univ-perp.archives-ouvertes.fr/hal-01212253/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01212253/file/1598-3145-1-PB.pdf
DOI : 10.3989/scimar.04225.31A

Éditeur(s) : HAL CCSD
Résumé : International audience
https://hal.archives-ouvertes.fr/hal-01436542

hal-01436542
https://hal.archives-ouvertes.fr/hal-01436542
DOI : 10.1109/IGARSS.2011.6049595

Éditeur(s) : HAL CCSD Western Indian Ocean Marine Science Association
Résumé : International audience
Juan de Nova is one of the scattered islands known as Iles Eparses in the Mozambique Channel (Western Indian Ocean). Historically, they have been isolated from many anthropogenic influences which makes them ideal areas to study biodiversity for comparison with areas that are heavily impacted by urbanization and fishing. The programme BioReCie (Biodiversity, Resources and Conservation of Eparses Islands) undertook inventories of several marine groups, including echinoderms, which had hitherto not been assessed in Juan de Nova. A multidisciplinary team surveyed the reef slopes of the island using SCUBA to a depth of 25 m as well as the reef flats at low tide, collecting specimens and taking photos for identification. Sixty echinoderm species were found, with 51 occurring on the reef flats and in the lagoon and 22 on the reef slopes, comprising 21 species of Holothuroidea, 16 Ophiuroidea, 10 Echinoidea, 7 Asteroidea, and 6 Crinoidea. Commercial species of Holothuroidea, some of which are classified as endangered in the IUCN red list, i.e. Thelenota ananas and Holothuria nobilis, were present on the reef flats, reef slopes and in the lagoon of the island, indicating the value that protection has on biodiversity.
ISSN: 0856-860X

hal-01306709
http://hal.univ-reunion.fr/hal-01306709
http://hal.univ-reunion.fr/hal-01306709/document
http://hal.univ-reunion.fr/hal-01306709/file/A%20First%20Inventory%20of%20Echinodermata%20at%20Juan%20de%20Nova_hal.pdf

Éditeur(s) : HAL CCSD The Royal Society
Résumé : International audience
Conservation commonly requires trade-offs between social and ecological goals. For tropical small-scale fisheries, spatial scales of socially appropriate management are generally small— the median no-take locally managed marine area (LMMA) area throughout the Pacific is less than 1 km 2. This is of particular concern for large coral reef fishes, such as many species of grouper, which migrate to aggregations to spawn. Current data suggest that the catchment areas (i.e. total area from which individuals are drawn) of such aggregations are at spatial scales that preclude effective community-based management with no-take LMMAs. We used acoustic telemetry and tag-returns to examine reproductive migrations and catchment areas of the grouper Epinephelus fuscoguttatus at a spawning aggregation in Papua New Guinea. Protection of the resultant catchment area of approximately 16 km 2 using a no-take LMMA is socially untenable here and throughout much of the Pacific region. However, we found that spawning migrations were skewed towards shorter distances. Consequently, expanding the current 0.2 km 2 no-take LMMA to 1–2 km 2 would protect approximately 30–50% of the spawning population throughout the non-spawning season. Contrasting with current knowledge, our results demonstrate that species with moderate reproductive migrations can be managed at scales congruous with spatially restricted management tools.
ISSN: 2054-5703

Droits : http://creativecommons.org/licenses/by/
hal-01297717
https://hal-univ-perp.archives-ouvertes.fr/hal-01297717
https://hal-univ-perp.archives-ouvertes.fr/hal-01297717/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01297717/file/150694.full.pdf
DOI : 10.1098/rsos.150694

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Coral reef resource systems are complex adaptive social-ecological systems providing vital and valuableecosystem services for human societies such as food provision, coastal protection and recreational activities.Their sustainability is questioned in many places around the world as they experience combined effects ofmultiple chronic anthropogenic and natural drivers at local to global scales. From a management perspective,there is a crucial need to understand how the impact of these drivers cascade through the social-ecologicalsystem components. This study develops a transdisciplinary and participatory approach to investigating thesocial-ecological dynamics of a Polynesian coral reef coastal system. A preliminary conceptual model using theDriver-Pressure-State-Impact (DPSI) framework is first being built through participatory modeling workshops.Then, pressure-state relationships are assessed with the help of empirical datasets as a first step towards thevalidation of the DPSI model. Results shows striking social-ecological interactions with different patterns in thelagoon and in the fore reef. Local management should be: (1) less resource-focused to account more specificallyto the existing typology of actors; (2) more spatially-explicit to better distinguish management objectives andactions for the lagoon and the fore reef sub-systems; and (3) more coordinated with terrestrial agencies for acoherent land-sea connection and integration that would both (i) account for existing land-sea interactions and(ii) better reflect the Polynesian cultural heritage that considers nature from ridge to reef as a whole. Suchconceptual models of social-ecological systems are a useful tool to build exploratory scenarios to ultimatelysupport planning decision-making processes.
ISSN: 0308-597X

hal-01491968
https://hal-univ-perp.archives-ouvertes.fr/hal-01491968
DOI : 10.1016/j.marpol.2017.01.014

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Despite the unique nature of endemic species, their origin and population history remain poorly studied. We investigated the population history of 28 coral reef fish species, close related, from the Gambier and Marquesas Islands, from five families, with range size varying from widespread to small-range endemic. We analyzed both mitochondrial and nuclear sequence data using neutrality test and Bayesian analysis (EBSP and ABC). We found evidence for demographic expansions for most species (24 of 28), irrespective of range size, reproduction strategy or archipelago. The timing of the expansions varied greatly among species, from 8,000 to 2,000,000 years ago. The typical hypothesis for reef fish that links population expansions to the Last Glacial Maximum fit for 14 of the 24 demographic expansions. We propose two evolutionary processes that could lead to expansions older than the LGM: (a) we are retrieving the signature of an old colonization process for widespread, large-range endemic and paleoendemic species or (b) speciation; the expansion reflects the birth of the species for neoendemic species. We show for the first time that the demographic histories of endemic and widespread reef fish are not distinctly different and suggest that a number of processes drive endemism.
ISSN: 2045-2322

hal-01469339
https://hal-univ-perp.archives-ouvertes.fr/hal-01469339
https://hal-univ-perp.archives-ouvertes.fr/hal-01469339/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01469339/file/population%20expansions.pdf
DOI : 10.1038/srep40519

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Large organic falls to the benthic environment, such as dead wood or whale bones, harbour organisms relying on sulfide-oxidizing symbionts. Nothing is known however, concerning sulfide enrichment at the wood surface and its relation to wood colonization by sulfide-oxidizing symbiotic organisms. In this study we combined in situ hydrogen sulfide and pH measurements on sunken wood, with associated fauna microscopy analyses in a tropical mangrove swamp. This shallow environment is known to harbour thiotrophic symbioses and is also abundantly supplied with sunken wood. A significant sulfide enrichment at the wood surface was revealed. A 72 h sequence of measurements emphasized the wide fluctuation of sulfide levels (0.1->100 lM) over time with both a tidal influence and rapid fluctuations. Protozoans observed on the wood surface were similar to Zoothamnium niveum and to vorticellids. Our SEM observations revealed their association with ectosymbiotic bacteria, which are likely to be sulfide- oxidizers. These results support the idea that sunken wood surfaces constitute an environment suitable for sulfide-oxidizing symbioses.
ISSN: 0141-1136

hal-00751649
https://hal.univ-antilles.fr/hal-00751649

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Infectious marine diseases can decimate populations and are increasing among some taxa due to global change and our increasing reliance on marine environments. Marine diseases become emergencies when significant ecological, economic or social impacts occur. We can prepare for and manage these emergencies through improved surveillance, and the development and iterative refinement of approaches to mitigate disease and its impacts. Improving surveillance requires fast, accurate diagnoses, forecasting disease risk and real-time monitoring of disease-promoting environmental conditions. Diversifying impact mitigation involves increasing host resilience to disease, reducing pathogen abundance and managing environmental factors that facilitate disease. Disease surveillance and mitigation can be adaptive if informed by research advances and catalysed by communication among observers, researchers and decision-makers using information-sharing platforms. Recent increases in the awareness of the threats posed by marine diseases may lead to policy frameworks that facilitate the responses and management that marine disease emergencies require.
ISSN: 0962-8436

hal-01282464
https://hal-univ-perp.archives-ouvertes.fr/hal-01282464
DOI : 10.1098/rstb.2015.0364

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Aim : To assess gaps in the representation of taxonomic, phylogenetic and functional diversity among coastal fishes in Mediterranean marine-protected areas (MPAs).
ISSN: 1366-9516

hal-01135644
https://hal.archives-ouvertes.fr/hal-01135644
DOI : 10.1111/ddi.12280

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The correlation between the flow turbulence and the performances of a ma- rine current turbine is studied. First, the incoming flow encountered in the flume tank is characterized in the framework of fully developed turbulent cascades in the inertial range. The Reynolds number, the Kolmogorov dissipation scale and the integral scale, are estimated from flow measurements. The intermittency of the turbulence is characterized in the lognormal multifractal framework, and the influence of the turbulent flow on the turbine power is assessed. The rotor speed control unit characteristics used for the turbine regulation induces non-negligible effects on the turbine behavior under fluctuations loads. Even if the power spectrum does not reveal any scale invariance, a multiscale analysis allows us to show the correlations between the turbulence time se- ries and the power produced. The classical Mean Square Coherency function shows that for scales larger than 10 seconds, the upstream velocity and power have large correlations. In the framework of the Empirical Mode Decomposition method, such correlations are studied using the time-dependence intrinsic corre- lation analysis method. This method allows to zoom into time-frequency scales where the flow perturbations induced some modifications in power production
ISSN: 0960-1481

hal-01528296
https://hal.archives-ouvertes.fr/hal-01528296
DOI : 10.1016/j.renene.2017.05.024

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Losses of corals worldwide emphasize the need to understand what drives reef decline. Stressors such as overfishing and nutrient pollution may reduce resilience of coral reefs by increasing coral–algal competition and reducing coral recruitment, growth and survivorship. Such effects may themselves develop via several mechanisms, including disruption of coral microbiomes. Here we report the results of a 3-year field experiment simulating overfishing and nutrient pollution. These stressors increase turf and macroalgal cover, destabilizing microbiomes, elevating putative pathogen loads, increasing disease more than twofold and increasing mortality up to eightfold. Above-average temperatures exacerbate these effects, further disrupting microbiomes of unhealthy corals and concentrating 80% of mortality in the warmest seasons. Surprisingly, nutrients also increase bacterial opportunism and mortality in corals bitten by parrotfish, turning normal trophic interactions deadly for corals. Thus, overfishing and nutrient pollution impact reefs down to microbial scales, killing corals by sensitizing them to predation, above-average temperatures and bacterial opportunism.
ISSN: 2041-1723

Droits : http://creativecommons.org/licenses/by/
hal-01340547
https://hal-univ-perp.archives-ouvertes.fr/hal-01340547
https://hal-univ-perp.archives-ouvertes.fr/hal-01340547/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01340547/file/ncomms11833.pdf
DOI : 10.1038/ncomms11833

Éditeur(s) : HAL CCSD Springer
Résumé : International audience
Microsatellite markers were developed for the coral reef fish Chaetodon vagabundus using shotgun pyrosequencing. As threats to coral reefs intensify, information on larval connectivity is of increasing value for efficient conservation planning. Here, 11 novel microsatellites were characterized for 192 individuals from Papua New Guinea. The number of alleles per locus ranged from 7 to 32, while observed and expected heterozygosity values varied from 0.214 to 0.903. These markers will be used to study population structure and larval connectivity of this iconic coral reef fish in coral reefs across the Indo-Pacific.
ISSN: 1877-7252

hal-01136139
https://hal.archives-ouvertes.fr/hal-01136139
DOI : 10.1007/s12686-015-0440-8

Éditeur(s) : HAL CCSD Station Biologique
Résumé : International audience
This study deals with temporal variations in eel diet Anguilla anguilla sampled at each of the four seasons in the Languedocian Prévost lagoon (Gulf of Lion) from Autumn 1998 to Summer 1999. The following feeding indices were calculated based on observations of 12 categories of prey found in the contents of full stomachs: coefficient of vacuity CV, degree of fullness DR, occurrence frequency PP, relative abundance N (in %) and relative weight P (in %). The interpretation of results is also based on the Costello's method (1990) which combines PP and N. Anguilla anguilla mainly feeds on benthic organisms, primarily Gammarus gr. locusta, Polychaeta, insect larvae, small fish. Based on variations in eel diet, seasonal influence is illustrated by a decrease in feeding activity in summer which gradually increases during the following seasons. The good trophic quality available to eels in the Prévost lagoon depends on its hydrodynamics which is directly related to the movement of water entering and leaving lagoon by a short communication with the sea. This water movement accelerates the enrichment and production processes of this ecosystem. Changes observed during the four seasons illustrate an opportunistic type of feeding behaviour. Eels consume the most available benthic prey. They favour the importance of the prey at a given moment without using a particular feeding strategy like specialisation or generalisation. Thus, eel adapts its diet in adjusting available energy resources in the ecosystem. Because of this, the lagoon-resident species Anguilla anguilla is an obvious indirect bioindicator of the trophic capacity and present level of confinement in the brackish water lagoon ecosystem of Prévost.
ISSN: 0007-9723

hal-00753021
https://hal.univ-antilles.fr/hal-00753021