Search

Marine organisms show population structure at a relatively fine spatial scale, even in open habitats. The tools commonly used to assess subtle patterns of connectivity have diverse levels of resolution and can complement each other to inform on population structure. We assessed and compared the discriminatory power of genetic markers and otolith shape to reveal the population structure on evolutionary and ecological time scales of the common sole (Solea solea), living in the Eastern English Channel (EEC) stock off France and the UK. First, we genotyped fish with Single Nucleotide Polymorphisms to assess population structure at an evolutionary scale. Then, we tested for spatial segregation of the subunits using otolith shape as an integrative tracer of life history. Finally, a supervised machine learning framework was applied to genotypes and otolith phenotypes to probabilistically assign adults to subunits and assess the discriminatory power of each approach. Low but significant genetic differentiation was found among subunits. Moreover, otolith shape appeared to vary spatially, suggesting spatial population structure at fine spatial scale. However, results of the supervised discriminant analyses failed to discriminate among subunits, especially for otolith shape. We suggest that the degree of population segregation may not be strong enough to allow for robust fish assignments. Finally, this study revealed a weak yet existing metapopulation structure of common sole at the fine spatial scale of the EEC based on genotypes and otolith shape, with one subunit being more isolated. Our study argues for the use of complementary tracers to investigate marine population structure. ispartof: PLOS ONE vol:15 issue:11 ispartof: location:United States status: published

We reviewed the use of survey-based pre-recruit abundance indices in short-term recruitment forecasts for fish species relying on coastal habitats at the juvenile stage and that are assessed by ICES. We collated information from stock assessment reports and from a questionnaire filled out by the stock assessors. Among the 78 stocks with juvenile coastal dependence, 49 use short-term forecasts in stock assessment. Survey-based pre-recruit abundance indices were available for 35 of these stocks, but only 14 were used to forecast recruitment. The questionnaire indicated that the limited use of survey-based pre-recruit abundance indices was primarily due to sampling inefficiency, which may preclude reliable recruitment estimates. The sampling is inefficient because the juvenile coastal distribution is outside the geographical area covered by large-scale surveys or targeted coastal surveys are conducted on limited spatial and temporal scales. However, our analysis of the relationship between survey-based pre-recruit indices and assessment-generated recruitment indices revealed that survey-based pre-recruit abundance indices were sufficiently accurate to provide useful information for predicting future recruitment. We recommend expansion of the use of survey-based indices of pre-recruit abundance in stock assessment and recruitment forecasting, and consideration of how to include juveniles in ongoing and future surveys.

Fundacao para a Ciencia e a Tecnologia (FCT) [IF/00058/2013, PTDC/AAG-GLO/5849/2014, UID/MAR/04292/]; European Commission via National Programme for Biological Sampling (PNAB) integrated in the Data Collection Framework; Wageningen Marine Research This work was developed within the context of the ICES Working Group on the Value of Coastal Habitats for Exploited Species (WGVHES). We thank both ICES and all participants of the Working Group during 2014-2017. Contributors to this research were independently funded and supported: EJB was funded by the Danish Recreational Fishers Fund - Marine Fiskepleje and the Otto Monsted Fund; RPV was financed through Fundacao para a Ciencia e a Tecnologia (FCT) via Investigador FCT Programme 2013 (IF/00058/2013), project PTDC/AAG-GLO/5849/2014 and project UID/MAR/04292/, and through European Commission via National Programme for Biological Sampling (PNAB) integrated in the Data Collection Framework, and KvdW was supported by Wageningen Marine Research.; International audience; Coastal ecosystems are ecologically, culturally, and economically important, and hence are under pressure from diverse human activities. We reviewed the literature for existing evidence of effects of human-induced habitat changes on exploited fish utilizing coastal habitats. We focused on fish species of the Northeast Atlantic for which fisheries advice is provided by International Council for the Exploration of the Sea (ICES) and which utilize coastal habitats for at least one life-history stage (LHS). We found that 92% of these species are impacted by human activity in at least one LHS while utilizing coastal habitat and 38% in multiple stages. Anthropogenic pressures most commonly shown to impact these fish species were toxicants and pollutants (75% of species). Eutrophication and anoxia, invasive species, and physical coastal development affected about half of the species (58, 54, and 42% of species, respectively), while indirect fishing impacts affected a minority (17% of species). Moreover, 71% of the ICES advice species that utilize coastal habitats face impacts from more than one pressure, implying cumulative effects. Given that three-fourths of the commercial landings come from fish species utilizing coastal habitats, there is an obvious need for a better understanding of the impacts that human activities cause in these habitats for the development of ecosystem-based fisheries management.

International audience; The delineation of essential fish habitats is necessary to identify, design and prioritize efficient marine protected area (MPA) networks with fishery objectives, capable, in addition to other possible objectives and functions of MPAs, of sustaining the renewal of marine living resources. Generally, the first step to obtain maps of essential fish habitats consists in choosing one of the numerous existing statistical approaches to build robust habitat suitability models linking relevant descriptors of the marine environment to the spatial distribution of fish presence or density. When these descriptors are exhaustively known, i.e. maps are available for each of them, geo-referenced predictions from these models and their related uncertainty may be imported into Geographic Information Systems for the quantitative identification and characterization of key sites for the marine living resources. The usefulness of such quantitative maps for management purposes is endless. These maps allow for the quantitative identification of the different habitats that are required for these marine resources to complete their life cycles and enable to measure their respective importance for population renewal and conservation. The consequences of anthropogenic pressures, not only fishing but also land reclamation, aggregate extractions or degradation of habitat quality (e.g. nutrient excess or xenobiotics loadings, invasive species or global change), on living resources, may also be simulated from such habitat models. These quantitative maps may serve as input in specific spatial planning software or to spatialise population or fishery dynamics, ecosystem or trophic models that may then be used to simulate various scenarios. Fish habitat maps thus may help decision makers to select relevant protection areas and design coherent MPA networks and management levels which objectives are to sustain fishing resources and fisheries.

International audience; Quantifying connectivity within fish metapopulations is an important component in understanding population dynamics and providing an evidence base for assessment and management. We investigate metapopulation connectivity of the common sole (Solea solea) in the Eastern English Channel (EEC). The EEC common sole stock is currently assessed as a single and spatially homogeneous population, but connectivity induced through adult movements within this stock and with nearby stocks remains unknown. To fill this knowledge gap, we developed a state-space mark-recovery model, designed to estimate adult connectivity using mark-recapture data from multiple release experiments from 1970 to 2018 across the EEC and adjacent management areas. The model estimates seasonal fish movements between five predefined areas, Western English Channel, Eastern English Channel (split into three discrete sub-areas), and North Sea. Over 32 000 fish were tagged, 4036 of which were recovered via fisheries. Our results suggest minimal large-scale adult movements between these areas; movements among spatial units within the EEC were very low with even lower levels of immigration from areas adjoining the EEC. Our results support the hypothesis of segregated populations within the EEC. The importance of accommodating population substructure in the fisheries management is considered.; La quantification de la connectivité au sein de métapopulations de poissons est un élément important pour comprendre la dynamique des populations et elle fournit des données probantes sur lesquelles baser l’évaluation et la gestion. Nous examinons la connectivité de métapopulations de sole (Solea solea) dans la Manche Est. Le stock de sole de la Manche Est est actuellement évalué en tant que population unique et homogène dans l’espace, mais une éventuelle connectivité induite par les déplacements d’adultes au sein de ce stock et par rapport à d’autres stocks à proximité demeure non caractérisée. Pour combler cette lacune, nous avons développé un modèle d’espace d’états de marquage-récupération conçu pour estimer la connectivité des adultes en utilisant des données de marquage-recapture de multiples expériences de remises à l’eau menées de 1970 à 2018 à la grandeur de la Manche Est et dans des aires de gestion attenantes. Le modèle estime les déplacements saisonniers de poissons entre cinq régions prédéfinies, soit la Manche Ouest, la Manche Est (subdivisée en trois sous-régions distinctes) et la mer du Nord. Plus de 32 000 poissons ont été marqués, dont 4036 ont été récupérés par la pêche. Nos résultats révèlent très peu de déplacements à grande échelle entre ces régions; les déplacements entre sous-régions de la Manche Est sont très faibles, et l’immigration en provenance de régions attenantes à la Manche Est, encore plus faible. Nos résultats appuient l’hypothèse de populations ségréguées dans la Manche Est. L’importance de la prise en compte de la sous-structure des populations dans la gestion des pêches est abordée.

International audience; An accurate representation of the spatial structure of marine fish populations is a prerequisite for unbiased stock assessment, to build appropriate management measures. The common sole (Solea solea, L.) of the Eastern English Channel (EEC) is a commercial flatfish species, whose stock is currently assessed as a single homogeneous population and has been overexploited over the last decade. Previous studies have highlighted the stock's low connectivity and the lack of understanding in sub-adults and adults mixing between putative subunits, raising the issue of a potential spatial structure of this stock. Here, we examined evidence of spatial structure by analyzing spatiotemporal patterns of length and density-at-age using time series (1989–2015) obtained from a scientific survey (UK-BTS). We tested for various hypotheses of spatial structure, based on both scientific and expert knowledge, including three isolated subunits, their combination, and no spatial structure. We combined two sets of analyses: (1) a selection of the von Bertalanffy growth model with spatial effects capturing the most accurate spatial structure of the stock and the analysis of long-term spatial patterns (gradients, trends, synchrony) in growth parameters; and (2) an analysis of the synchrony among density-at-age time series between spatial subunits. Growth analysis revealed a spatial structure in three subunits (i.e. the southwestern, northeastern and English parts of the EEC) and an overall decline of length-at-age, suggesting Fishery-Induced Evolution. The synchrony analysis revealed high spatiotemporal integrity at the level of the southwestern subunit of the EEC. Our two analyses thus detected a lasting signal of spatial stock structure with a probable isolation of the southwestern subunit from the rest of the EEC. Future research should build on our study by investigating the connectivity of sole throughout its entire life cycle, to improve stock assessment and fishery management.; Une représentation exacte de la structure spatiale des populations de poissons de mer est une condition préalable à une évaluation impartiale des stocks, afin d'élaborer des mesures de gestion appropriées. La sole commune (Solea solea, L.) de la Manche orientale (CEE) est une espèce commerciale de poisson plat, dont le stock est actuellement évalué comme une seule population homogène et a été surexploité au cours de la dernière décennie. Des études antérieures ont mis en évidence la faible connectivité du stock et le manque de compréhension chez les sous-adultes et les adultes se mélangeant entre sous-unités putatives, ce qui soulève la question d'une structure spatiale potentielle de ce stock. Nous avons examiné ici les preuves de la structure spatiale en analysant les tendances spatio-temporelles de la longueur et de la densité selon l'âge à l'aide de séries chronologiques (1989-2015) obtenues à partir d'une enquête scientifique (UK-BTS). Nous avons vérifié diverses hypothèses de structure spatiale, fondées sur des connaissances scientifiques et spécialisées, y compris trois sous-unités isolées, leur combinaison et l'absence de structure spatiale. Nous avons combiné deux ensembles d'analyses : (1) une sélection du modèle de croissance de von Bertalanffy avec des effets spatiaux capturant la structure spatiale la plus précise du stock et l'analyse des modèles spatiaux à long terme (gradients, tendances, synchronie) des paramètres de croissance ; et (2) une analyse de la synchronisation entre les séries temporelles de densité à âge entre sous-unités spatiales. L'analyse de la croissance a révélé une structure spatiale dans trois sous-unités (c'est-à-dire les parties sud-ouest, nord-est et anglaise de la CEE) et un déclin global de la longueur selon l'âge, ce qui suggère une évolution induite par la pêche. L'analyse synchrone a révélé une grande intégrité spatio-temporelle au niveau de la sous-unité sud-ouest de la CEE. Nos deux analyses ont ainsi détecté un signal durable de la structure spatiale du stock avec un isolement probable de la sous-unité sud-ouest du reste de la CEE. Les recherches futures devraient s'appuyer sur notre étude en étudiant la connectivité de la sole tout au long de son cycle de vie, afin d'améliorer l'évaluation des stocks et la gestion des pêches.

International audience; The sustainable exploitation of sea resources is based on the understanding of population distribution, structure and functioning. The mismatch between stock units and fish populations can dramatically bias the assessment and lead to irrelevant or even detrimental management measures. The common sole of the Eastern English Channel (EEC; ICES division VIId) is a flatfish species of high interest that has been overexploited over the last decades. Low connectivity induced by early life stages across the stock was previously known, but gaps remained regarding the role of adults in population connectivity and spatial structure. In this study we have filled these gaps by (1) gathering all the information on stock identity through five population- and individual-based approaches, and (2) combining this information in a semi-quantitative framework, i.e. the Stock Differentiation Index (SDI). Regarding the population-based approaches, growth and abundance-at-age analyses highlighted a lasting signal of population structure, with three population subunits. Regarding the individual-based approaches, genetic analysis highlighted low but significant genetic differentiation between the three subunits over an evolutionary time scale. Besides, a mark-recapture study demonstrated a low level of exchange between these subunits. Finally, an analysis of otolith shape pinpointed spatial variation between the three subunits. Overall, the SDI = 0.93 suggested evidence of spatial structure. The misalignment of the current stock definition with the underlying biological metapopulation now requires the improvement of the assessment-management to ensure its sustainable exploitation.

Cet article se propose d’expliquer, sur l’exemple de l’ichtyofaune des masses d’eau de transition, la demarche adoptee par la France pour repondre aux objectifs de la DCE et les defis qu’elle presentait dans des delais contraints. Nous presentons le vide de connaissances et de donnees qui regnait au debut des annees 2000 et les actions mises en œuvre au pas de charge pour repondre aux objectifs ambitieux de la DCE, disposer d’un reseau de surveillance en 2007, puis d’indicateurs normes decrivant l’etat ecologique afin de presenter un bilan six ans plus tard, en 2013, a l’issue du premier plan de gestion. Il reste desormais a poursuivre la demarche en milieu marin dans le cadre de la DCSMM.

Some of the research leading to these results has received funding from the European Union through the European Community's Seventh Framework Program (FP7/2007-2013) under Grant Agreement No. 266445 for the project "Vectors of Change in Oceans and Seas Marine Life, Impact on Economic Sectors (VECTORS)." Additional work resulted from the BONUS BALTSPACE project (Towards Sustainable Governance of Baltic Marine Space), supported by BONUS (Art 185), funded jointly by the EU and by national research funding agencies in the eight EU member states around the Baltic Sea.; International audience; The relationship between fisheries and marine spatial planning (MSP) is still widely unsettled. While several scientific studies highlight the strong relation between fisheries and MSP, as well as ways in which fisheries could be included in MSP, the actual integration of fisheries into MSP often fails. In this article, we review the state of the art and latest progress in research on various challenges in the integration of fisheries into MSP. The reviewed studies address a wide range of integration challenges, starting with techniques to analyse where fishermen actually fish, assessing the drivers for fishermen's behaviour, seasonal dynamics and long-term spatial changes of commercial fish species under various anthropogenic pressures along their successive life stages, the effects of spatial competition on fisheries and projections on those spaces that might become important fishing areas in the future, and finally, examining how fisheries could benefit from MSP. This paper gives an overview of the latest developments on concepts, tools, and methods. It becomes apparent that the spatial and temporal dynamics of fish and fisheries, as well as the definition of spatial preferences, remain major challenges, but that an integration of fisheries is already possible today. (C) 2017 The Authors. Published by Elsevier Ltd.

Burgess et al.’s report in PNAS, “Range contraction enables harvesting to extinction” (1), provides a highly valuable perspective on the consequences of species range contractions that maintain local densities of declining populations. The authors suggest that this density-dependent contraction maintains local harvesting yields and economic incentives that enable depleted natural populations of both marine and terrestrial species to be harvested until collapse and extinction. Burgess et al.’s approach, combining modeling and empirical review, covers a large spectrum of species with convincing … [↵][1]1To whom correspondence should be addressed. Email: olivier.le.pape{at}agrocampus-ouest.fr. [1]: #xref-corresp-1-1

[Departement_IRSTEA]Eaux [Departement_IRSTEA]Ecotechnologies [Departement_IRSTEA]Territoires [TR1_IRSTEA]BELCA [TR2_IRSTEA]TED [TR2_IRSTEA]DTAM [TR2_IRSTEA]QUASARE [Type_IRSTEA]Rapport d'expertise; Synthèse du rapport d'une expertise scientifique collective. Elle établit un état des lieux critique sur les connaissances scientifiques disponibles au plan international sur les causes, les mécanismes, les conséquences et la prédictibilité des phénomènes d'eutrophisation.

This paper examines the effect of climate warming on the bio-economic performance of Bay of Biscay mixed fisheries and provides insights into the best management strategy for coping with global warming. To achieve this, a dynamic multi-species, multi-class, multi-fleets model is developed and calibrated using biological and environmental ICES and IPCC data. Fishing and economic data have been collected within the European DCF. The climate represented by the Sea Surface temperature is assumed to affect species recruitment. Three management strategies are then compared in terms of bio-economic outcomes: Status-Quo (SQ), Multi-species Maximum Sustainable Yield (MMSY), Multispecies Maximum Economic Yield (MMEY). Strategies are ranked with respect to two climate scenarios. Results exhibit that the SQ strategy is not sustainable and is characterized by a major decline of Sole. By contrast, the MMSY and the MMEY strategies improve the ecological state and economic performance of fisheries. Furthermore, the MMEY strategy provides higher bio-economic performances than MMSY. These bio-economic benefits are however altered by climate change effects. Under the MMEY, fleets with more diversified catches perform better facing climate change., Cet article étudie l'effet du réchauffement climatique sur les performances bio-économiques des pêcheries mixtes du golfe de Gascogne et fournit un aperçu de la meilleure stratégie de gestion pour faire face au réchauffement climatique. Pour ce faire, un modèle dynamique multi-espèces, multi-classes, multi-flottilles est développé et calibré à l'aide de données biologiques et environnementales du CIEM et du GIEC. Des données économiques et de pêche ont été collectées au sein du DCF européen. Le climat, représenté par la température de la surface de la mer, est supposé affecter le recrutement des espèces. Trois stratégies de gestion sont ensuite comparées en termes de résultats bio-économiques : Statu-Quo (SQ), Multi-species Maximum Sustainable Yield (MMSY), Multi-species Maximum Economic Yield (MMEY), Les stratégies sont classées en fonction de deux scénarios climatiques. Les résultats démontrent que la stratégie SQ n'est pas durable et qu'elle se caractérise par un déclin majeur de la sole. En revanche, les stratégies MMSY et MMEY améliorent l'état écologique et les performances économiques des pêcheries. De plus, la stratégie MMEY produit des performances bio-économiques supérieures à la stratégie MMSY. Ces bénéfices bio-économiques sont cependant altérés par les effets du changement climatique. Dans le cadre du MMEY, les flottilles dotées de captures plus diversifiées sont plus performantes face aux changements climatiques.

Trophic levels are critical for synthesizing species' diets, depicting energy pathways, understanding food web dynamics and ecosystem functioning, and monitoring ecosystem health. Specifically, trophic levels describe the position of species in a food web, from primary producers to apex predators (range, 1-5). Small differences in trophic level can reflect large differences in diet. Although trophic levels are among the most basic information collected for animals in ecosystems, a human trophic level (HTL) has never been defined. Here, we find a global HTL of 2.21, i.e., the trophic level of anchoveta. This value has increased with time, consistent with the global trend toward diets higher in meat. National HTLs ranging between 2.04 and 2.57 reflect a broad diversity of diet, although cluster analysis of countries with similar dietary trends reveals only five major groups. We find significant links between socio-economic and environmental indicators and global dietary trends. We demonstrate that the HTL is a synthetic index to monitor human diets and provides a baseline to compare diets between countries.

Juveniles of numerous commercial marine flatfish species use coastal and estuarine habitats as nurseries. Hence, they are likely to be exposed to a number of anthropogenic stressors such as accidental and chronic exposure to chemical contaminants. Little is known about their response to such pollutants at the individual level and about the consequences on their population dynamics. Mesocosm experiments were conducted to determine whether short (24 h) but high exposure to petroleum hydrocarbons (1/1000 v: v water: fuel), similar to what happened after an oil spill on coastal areas, affects survival and biological (growth, body condition and lipid reserve) performances of juvenile common sole, which live on near shore and estuarine nursery grounds. Results demonstrated that this type of exposure significantly reduce survival, growth (size, recent otolith increment and body condition), and especially energy storage (triacylglycerol to free sterol ratio) of the juvenile fish on the medium-term (three months after the exposure). These medium-term consequences affect future recruitment of this long- lived species.

International audience; We explore how alternative hypotheses on the degree of mixing among local subpopulations affect statistical inferences on the dynamics and stock assessment of a harvested flatfish population, namely, the common sole population in the Eastern Channel (ICES area VIId). The current paradigm considers a single, well-mixed, spatially homogeneous population with juveniles from all coastal nursery grounds along the French and UK coasts that contribute to a single adult population and one pool of eggs. Based on the available data and ecological knowledge, we developed a spatial Bayesian integrated life-cycle model that consists of three subpopulations (one near the UK coast and two near the French coast, denoted UK, West FR and East FR, respectively) supported by their respective local nurseries, with the connectivity among the three components limited to low exchanges during larval drift. Considering the population dynamics among three subpopulations (instead of a single homogeneous one) drastically changes our inferences on the productivity of nursery sectors and their relative contribution to total recruitment. Estimates of the East FR subpopulation’s contribution to total recruitment increase (29% in the single population model; 48% in the three subpopulation model), balanced by a decrease in the UK subpopulation’s contribution (53%; 34%). Whereas an assessment based on the hypothesis of a single spatially homogeneous population in the EC indicates exploitation far above MSY (current F/FMSY = 1.8), an assessment that considers a metapopulation with three loosely connected subpopulations revealed a different status, with the UK and East FR subpopulations being exploited above MSY (current F/FMSY = 1.9 and 2, respectively) and the West FR subpopulation approaching full exploitation (current F/FMSY = 1.05). This approach contributes to the quantitative assessment of spatial fishery and coastal habitat management plans.

For many marine fish species, recruitment is strongly related to larval survival and dispersal to nursery areas. Simulating larval drift should help assessing the sensitivity of recruitment variability to early life history. An individual-based model (IBM) coupled to a hydrodynamic model was used to simulate common sole larval supply from spawning areas to coastal and estuarine nursery grounds at the population scale in the eastern Channel on a 14-yr time series, from 1991 to 2004. The IBM allowed each particle released to be transported by currents from the hydrodynamic model, to grow with temperature, to migrate vertically giving stage development, and possibly to die according to drift duration, representing the life history from spawning to metamorphosis. Despite sensitivity to the larval mortality rate, the model provided realistic simulations of cohort decline and spatio-temporal variability of larval supply. The model outputs were analysed to explore the effects of hydrodynamics and life history on the interannual variability of settled sole larvae in coastal nurseries. Different hypotheses of the spawning spatial distribution were also tested, comparing homogeneous egg distribution to observation and potential larval survival (PLS) maps. The sensitivity analyses demonstrated that larval supply is more sensitive to the life history along larval drift than to the phenology and volume of spawning, providing explanations for the lack of significant stock–recruitment relationship. Nevertheless, larval supply is sensitive to spawning distribution. Results also suggested a very low connectivity between supposed different sub-populations in the eastern Channel.

Oceanic larvae of the European (Anguilla anguilla) and American (A. rostrata) eels have to cross the Atlantic Ocean from the Sargasso Sea to European or North American coasts before entering continental habitats. In some European rivers, eel recruitment is now

Estuarine fish assemblages are subject to a great environmental variability that largely depends on both upstream fluvial and downstream marine influences. From this ecohydrological view, our study introduces a macroecological approach aiming to identify the main environmental factors that structure fish assemblages among European tidal estuaries. The present paper focuses on the influence of large scale environmental gradients on estuarine fish species richness. The environment of 135 North-eastern Atlantic estuaries from Portugal to Scotland was characterized by various descriptors especially related to hydromorphology. Major environmental trends among estuaries were underlined using multivariate techniques and cluster analyses applied to abiotic data. In particular, an integrative system size covariate was derived from a principal component analysis. Factors explaining patterns of species richness at different scales from local habitat to regional features were highlighted. Based on generalised linear models, the estuarine system size, and more particularly the entrance width, and also the continental shelf width were identified as the best explanatory variables of estuarine fish species richness at a large scale. Our approach provides a standardized method to estimate the relationship between fish assemblages and environmental factors. This constitutes a first step in assessing estuarine ecological status and studying the effects of additional factors such as anthropogenic disturbances.

International audience; The migration duration of European eel (Anguilla anguilla) larvae (leptocephali) from the spawning areas in the Sargasso Sea to the European continental shelf remains highly controversial, with estimates varying from 6 months to more than 2 yr. We estimated the fastest migration period and the shortest distance travelled by eel larvae by simulating Lagrangian particles released in the Sargasso Sea and by simulating a range of larval behaviours (fixed-depth drift, vertical diurnal migration and active-depth selection to maximize current velocity). This enabled us to compute (i) a passive drift speed, and (ii) a hypothetic swimming speed needed for European eel larvae to cross the Atlantic in 6 months (i.e., the migration duration estimated from otolith daily growth increments). Our results show that the minimum travel time for an eel larva that is passively drifting was 10 months and 3 days. Active behaviours (vertical diurnal migration and rheotaxis) paradoxically increased the migration period. We found that for leptocephali to cross the Atlantic Ocean in 6 months, they would need to swim a minimum of 3.4 body lengths per second for 8200 km. No larvae have been observed with such swimming capabilities. These results provide evidence that leptocephali cannot cross the Atlantic in 6 months.

This study describes the spatial distribution of young-of-the-year common sole based on beam trawl surveys conducted in late summer in the coastal and estuarine parts of the Bay of Biscay (France). Previous studies showed that habitat suitability for juvenile common sole varies according to physical factors and notably bathymetry and sediment structure. Nevertheless, the use of these descriptors alone to model habitat suitability led to considerable unexplained variability in juvenile common sole distribution. Hence, the epibenthic macro- and megafauna collected during beam trawl surveys was taken into account to improve models of habitat suitability for these juvenile flatfish. Ecotrophic guilds based on life traits (behaviour, mobility and feeding) were used to develop generic indicators of trawled benthic fauna. These synthetic descriptors were used in generalized linear models of habitat suitability in order to characterize the distribution of juvenile common sole. This approach significantly improved the description based on physical descriptors and allowed demonstrating that young common sole distribution is related to the density of trawled deposit and suspension feeders and also of carnivorous organisms. These models provide a reliable method to develop indicators of nursery habitat suitability from trawl survey data with the aim of assessing and surveying their quality. (c) 2006 Elsevier B.V. All rights reserved.

Coastal zones are productive areas that serve as nursery grounds for a large number of marine species. However, the processes involved in survival success during the juvenile phase are not well-known. Some authors suggest that the availability of prey is important to support the production of pre-recruit fish whose fitness is enhanced through optimal feeding conditions. Accordingly, recruitment is limited by the carrying capacity of the nursery habitat. In contrast, other authors state that the carrying capacity of the nursery grounds is not fully exploited, suggesting that there is no effect of food limitation. This study combines an overview of the literature, focused on flatfish that are especially dependent on coastal and estuarine nursery grounds, an extension to other marine fishes and a modelling approach on growth and survival of juvenile fish to explore the controversy of food limitation in their nursery grounds. We demonstrate that the relative lack of growth limitation observed for young marine fishes at the individual scale is related to an observational bias: fish have been affected by size-selective mortality linked to food limitation, but only surviving individuals are observed. As the population is skewed towards the faster-growing juveniles, the growth of survivors remains close to optimal, even when food resources are limited. Food limitation is of major influence in determining the carrying capacity of the nursery habitat. To sustain marine fish populations and related fisheries, management action is needed to protect coastal and estuarine areas and maintain or restore nursery productivity.

International audience; In this paper, we propose to study fish in transitional waters to illustrate the challenge of meeting the goals of the European Water Framework Directive in France in restricted delays. We present the lack of knowledge and data in early 2000s and the actions led then to achieve the ambitious objectives of the WFD: the creation of a standardized monitoring network in 2007 and the definition of ecological indicators based on the fish community. In 2013, at the end of the first management plan, an assessment of the ecological status was presented.; Cet article se propose d'expliquer, sur l'exemple de l'ichtyosaure des masses d'eau de transition, la démarche adoptée par la France pour répondre aux objectifs de la DCE et les défis qu'elle présentait dans les délais contraints. Nous présentons le vide de connaissances et de données qui régnait au début des années 2000 et les actions mises en oeuvre au pas de charge pour répondre aux objectifs ambitieux de la DCE, disposer d'un réseau de surveillance en 2007, puis d'indicateurs normés décrivant l'état écologique afin de présenter un bilan six ans plus tard, en 2013, à l'issue du premier plan de gestion.

Proceedings of the 15th French-Japanese Oceanography Symposium; International audience; Considerable research has been conducted in the past 15 years around the Eastern English Channel ecosystem. Data collected since the 1970s on the biotic and abiotic compartments have been collated and mapped out in the mid-2000. This spatially explicit information formed a sound basis to improve knowledge on, and model, the functioning and dynamics of key ecosystem compartments, with a focus on flatfish species and fisheries and their interactions with other sectors of activity (aggregate extractions, maritime traffic). The more recent ongoing works are dedicated to the integration of those processes into several complementary end-to-end ecosystem models.

This study describes the spatial distribution of young-of-the-year sole based on autumnal beam trawl surveys conducted in the Bay of Biscay (France) during a 15-y period. Previous studies showed that habitat suitability for juvenile sole varies according to physical factors such as bathymetry, sediment structure and river plume influence. These factors, which are known exhaustively for the entire Bay of Biscay from static maps (bathymetry and granulometry) or temporal maps based on a hydrodynamic model (the river plume), were used as descriptors in a generalised linear model of habitat suitability in order to characterise the distribution of juvenile 0-group sole according to delta distribution. This model was used to identify the habitats in which juvenile 0-group sole are concentrated. The respective areas of these habitats were determined from a Geographic Information System (GIS), and their respective contribution to the sole population in the Bay of Biscay was calculated in terms of the estimated number of young fish (GIS area×density derived from the model). Despite the great variability of survey data, this quantitative approach emphasises the highly important role of restricted shallow, muddy estuarine areas as nursery grounds of sole in the Bay of Biscay and demonstrates the relation between interannual variations of nursery habitat capacity (with respect to estuarine extent) and sole recruitment.

Roopnarine (1) suggests that the significance of the human trophic level (HTL) (2) is reduced because it defines the position of humans in the food web by diet and is not representative of our functional role in the ecosystem. He is concerned that humans are compared with low trophic level omnivores and asserts that we are apex predators because in marine systems, our extraction of wild fish is linked to high trophic level species. Our report demonstrates that humans are low trophic level omnivores because globally we eat more plant than meat. This fact remains, regardless of the functional role of humans in the ecosystem. … [↵][1]1To whom correspondence should be addressed. E-mail: anne.elise.nieblas{at}gmail.com. [1]: #xref-corresp-1-1

Feeley and Machovina assert that even though humans occupy a low trophic level, we have larger ecosystem impacts than any other species because of the sheer volume of food consumed (linked to population size) and the inefficiency of its production (1). The authors argue that large differences in the impact on resource use exist between dietary preferences (e.g., differing proportions of beef, pork, or poultry in a diet), even if human diets are represented by the same trophic level. We are in complete agreement that humans have among the largest ecological impact of any species and that the human trophic level (HTL) (2) does not capture … [↵][1]1To whom correspondence should be addressed. E-mail: sylvain.bonhommeau{at}ifremer.fr. [1]: #xref-corresp-1-1

Population dynamics are governed by four demographic rates: births, deaths, immigration, and emigration. Variation in these rates and processes underlying such variation can be used to prioritize habitat conservation and restoration as well as to parameterize models that predict habitat-specific effects on population dynamics. The current understanding of patterns of habitat-specific demographic variability in exploited marine species, as well as processes underlying these patterns, was reviewed. We describe patterns of (i) habitat-specific density, followed by ontogenetic changes in habitat use, such as (ii) immigration (i.e. use as a settlement habitat) and (iii) emigration (i.e. use as a habitat for secondary dispersal to and from), and demographic rates such as (iv) growth, and (v) mortality. Despite the importance of coastal habitats for fish and invertebrate species and the vulnerability of these habitats to human impacts, there was ambiguous evidence on their role in driving of population dynamics. Roughly 63% of the studies were descriptive, 21% experimental, and 11% used a combination of descriptive and experimental approaches, whereas 5% used meta-analyses. Habitat-specific density was the most common pattern quantified, followed by growth and mortality, with relatively few examples of studies of habitat-specific larval settlement. There were many examples of the influence of coastal habitats on survival, growth, and movement, especially at young stages, and there was an emerging focus on the effects of habitat degradation on demographic rates. There needs to be an increased effort on quantifying habitat-specific demographic rates and integrating these to better predict the effects of coastal habitats on the dynamics of exploited marine populations.

Many Pacific countries face socio-economic changes, resulting in an increase in fishing pressure on reef fish resources. In coral reef environments, examining the ecological effects of fishing on fish assemblages is generally hampered by the lack of data for both in situ assemblages and fishing activities, and by the difficulty to account for natural variations in assemblages. The responses of fish assemblages to moderate fishing pressure were investigated in two sites of New Caledonia (South Pacific). Habitat structures and fish assemblages were described through in situ multiyear underwater visual surveys to account for spatial and temporal variability. A recent quantification of fishing catches and efforts allowed defining spatial gradients of fishing pressure. Linear models were used to test fishing effects on species richness, density, biomass, length and trophic structure of the whole assemblage, large species, target species, and different ecotrophic guilds. A significant decrease in most metrics was detected when fishing pressure increased. The results obtained for all-species fish metrics were confirmed for target species, large species, carnivores and corallivores trophic guilds and large individuals. This functional modelling approach accounted for the natural variability of local coral reef systems and allowed detecting effects of fishing, although fishing pressure was low to moderate in the surveyed sites. Our results suggest that further modelling development, including control sites, would allow precautionary indicators and strategies to be defined for the monitoring and management of reef fish resources. (C) 2014 Elsevier Ltd. All rights reserved.

The Eastern Channel (ICES division 7d) is considered a unit for stock management of the common sole Solea solea and the plaice Pleuronectes platessa. At this scale, the aim of this work is to model the juvenile distribution of these flatfish. The database used, based on different surveys undertaken during the two last decades, includes 4500 coastal beam trawl hauls throughout the Eastern Channel coasts. Multivariate analyses are used to study the interannual fluctuations in flatfish recruitment of the region. This approach allows us to separate the Eastern Channel into homogeneous sectors with regard to these fluctuations. The physical parameters that contribute to the observed juvenile sole and plaice distributions are identified and their distributions are modelled using generalized linear models. The results of these models, and the areas of the different populations derived from a geographic information system, are used to identify the main nursery grounds and to compare their respective importance. This quantitative approach identifies the lack of estuarine dependence of the nursery grounds, and highlights those areas where anthropogenic disturbance could influence these populations. © 2001 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS statistical models / geographical information system / nursery grounds / Pleuronectes platessa / Solea solea / Eastern Channel

The Bay of Brest is a semi-enclosed coastal ecosystem where primary production is nutrient-limited, even if huge nutrients loading from tributaries are present. The most striking feature of the bay is the semi-diurnal tidal influence, resulting in large water exchange with the continental shelf. A historical study of the available data has shown the steadiness of this ecosystem during the two last decades in spite of increasing eutrophic conditions. This study has focused on hydrodynamic exchange which is one of the factors supposed to explain the resistance of this ecosystem to eutrophication: this stirring hinders the formation of a persistent upper mixed layer where phytoplankton would be in contact with nutrient-rich brackish waters and available light. Moreover, horizontal tidal currents lead to huge exchanges with the Iroise Sea and, then, to big losses of nutrients and living matter. To study this hydrodynamic influence thoroughly, a physical/biological model of this bay has been developed. This box model, based on the horizontal tidal circulation, has been developed thanks to “ELISE”, an ecological modelling software and, then, tuned and validated on two data sets corresponding with the years 1977 and 1993. The model has allowed us to quantify the influence of hydrodynamics, climatic conditions and biological factors on biogeochemical processes in this ecosystem. It contributes to explain the good resistance of the Bay of Brest ecosystem to eutrophic conditions; both the hydrodynamic properties of this bay and the grazing pressure have prevented it from disturbances caused by high nitrogen loading from the watersheds and explain the steadiness of phytoplankton stocks in spite of increased loading. So, these results allow us to say that, even if nitrogen inputs increase continues, phytoplankton stocks will not increase in significant proportions. Nevertheless, changes in the phytoplanktonic populations may occur if such an enrichment continues.

Through a review of the scientific literature and a more in-depth qualitative meta-analysis of 16 case studies distributed worldwide, this article aims to study impacts of MPAs on marine living resources, ecosystems and related fisheries and to highlight their criteria of efficiency as management tools for a sustainable exploitation. MPAs are efficient for conservation purposes and resource restoration, especially inside their borders. MPAs can also be part of fisheries management systems, but there is a lack of knowledge about their wider scale impacts on fish stocks, ecosystem and fisheries. Adjacent fisheries can increase their catches near closed areas, but such effects are delayed until after MPA establishment and are often limited over distance. Even though local specificities in ecosystems and fishing resources lead to high variability in MPA effects, four major criteria modulate the efficiency of MPAs for fisheries management: (1) the size of the closed area; (2) the level of protection of essential habitats for exploited resources; (3) MPA integration as part of wider integrated fisheries management plans; and (4) efficient monitoring and regulation systems, including participative decision making, to ensure that restrictive measures are respected.

absent

The Bay of Brest is a semi-enclosed coastal ecosystem receiving high nutrients loading from freshwater inputs. In order to analyse the response of phytoplankton stocks to increasing eutrophic conditions, a survey of the annual cycle of hydrographic properties, nutrients and chlorophyll a concentrations, and carbon uptake rates was performed at four stations in 1993. This database has been compared to earlier measurements performed during several comparable surveys within the last 20 years. As compared to the seventies, a doubled nitrate loading is now entering this ecosystem, which is related to increased agricultural activities on the drainage basins, while the geographical origin of the nitrate input has been modified. As a result of these anthropogenic modifications, summer averaged Si/N stoichiometric balance has decreased during the two last decades but, contrary to what has been observed in other coastal ecosystems, phytoplankton stocks have not increased. Several ecological factors have hindered eutrophication: the high hydrodynamic mixing with adjacent marine waters, caused by the macrotidal regime, induces important nutrients losses, temperature and mostly light limit primary production while Si and P high recycling maintain nitrogen limitation in this ecosystem. Conjunction of these non-anthropogenic factors explains the global stability of phytoplankton stocks.

International audience; Primary production must constrain the amount of fish and invertebrates available to expanding fisheries; however the degree of limitation has only been demonstrated at regional scales to date. Here we show that phytoplanktonic primary production, estimated from an ocean-colour satellite (SeaWiFS), is related to global fisheries catches at the scale of Large Marine Ecosystems, while accounting for temperature and ecological factors such as ecosystem size and type, species richness, animal body size, and the degree and nature of fisheries exploitation. Indeed we show that global fisheries catches since 1950 have been increasingly constrained by the amount of primary production. The primary production appropriated by current global fisheries is 17-112% higher than that appropriated by sustainable fisheries. Global primary production appears to be declining, in some part due to climate variability and change, with consequences for the near future fisheries catches.

The aim of the present study was to analyse the influence of warming on flatfish populations in the Bay of Biscay. 17 autumn cruises conducted from 1987 to 2006 over the whole shelf of the Bay of Biscay provided data for the abundance and occurrence of adults for twenty flatfish species. Trends in flatfish abundance were analysed with regard to geographic range of populations and interannual fluctuations in abundance were related to seawater temperature. Results showed significant trends in abundance and occurrence for 55% of the flatfish species in the Bay of Biscay. The response to warming of seawater was correlated to geographic ranges of species. While the abundance of the northern temperate species decreased, that of southern ones increased. Moreover, for 40% of the species which densities have significantly changed, abundances were correlated to temperatures in their year of birth, positively for southern species and negatively for northern ones. List, the abundance of flatfish adults over the Bay of Biscay was compared to previous data on juveniles in the Bay of Vilaine, one of the estuarine nursery ground in this area. For the northern species which have disappeared, the decline in juvenile abundances preceded that of adults by several years, indicating that the recruitment is the process affected. We concluded on a major impact of warming to explain changes in flatfish species abundances. Nevertheless, the impact of fishing interacts with that of climate change because the exploited species appeared to be the most negatively affected. (C) 2009 Elsevier B.V. All rights reserved.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE; National audience; Présentation des principaux résultats et préconisations pour l'action publique. Mise en application de l'indicateur et évolution de cet indicateur poisson depuis l'achèvement du projet Liteau II.

Glass eel abundances are declining worldwide. This has mostly been attributed to direct impacts of human activities such as overfishing or habitat loss and degradation, whilst the potential influence of changes in oceanic conditions has received less attention. Eel are characterized by a complex and still enigmatic life cycle that includes a trans-oceanic spawning and larval migration. The apparent synchrony in the decline of eel populations worldwide suggests that the oceanic mechanisms involved are similar for all populations. We analyse the relationships between oceanic conditions in eel spawning areas and glass eel recruitment success of the 3 most commercially important species of the genus Anguilla: A. anguilla, A. rostrata, and A. japonica. We provide evidence that the survival of eel larvae is strongly correlated with food availability during their early life stages. Over the last 4 decades, changes in the marine production related to global warming may have led to the decline of European, American and Japanese eel populations. In the Pacific and Atlantic Oceans, the shifts in the temperature regime detected in the late 1970s were followed by shifts in the recruitment regime of glass eel for the 3 species. The decrease in primary production through climate-driven processes has therefore affected the recruitment of eel populations.

National audience; L'indicateur poisson pour les eaux de transition a été développé en recherchant les réponses des peuplements de poissons aux différents types de pression qui s'exercent sur ces masses d'eau. Un groupe d'expert a établie les réponses attendues pour une sélection de métriques candidates face à une augmentation des pressions. A partir de cette liste de 32 métriques candidates, des tests de corrélation ont été réalisé pour éliminer les redondances. Nous avons ensuite testé à l'aide de modèles linéaires généralisés les réponses de chaque métrique restante en fonction des niveaux de pression pour retenir à la fin 4 métriques de densité pour les estuaires qui répondent à des pressions de pollution et 3 métriques pour les lagunes qui répondent à des pressions d'occupation des sols rivulaires. Les métriques actuellement retenues sont robustes et des seuils de classe peuvent être calculés. Cependant, la référence de très bon état reste toujours à modéliser. Le faible nombre de métriques nous semble apporter un risque supplémentaire de mauvais diagnostic et des métrique complémentaires sont actuellement recherchées pour réduire les risques de classement erroné.

National audience; Les masses d'eau de transition (MET estuaires et lagunes), telles que définies par la Directive Cadre sur l'Eau (DCE directive 2000/60/CE), assurent une fonction de nourricerie pour de nombreuses espèces de poissons marins. Elles sont néanmoins soumises à de fortes pressions anthropiques qui conduisent à la destruction de l'habitat et à la dégradation de sa qualité, et mettent en danger le renouvellement des espèces concernées. Pour le suivi de l'état des MET, la DCE institutionnalise, entre autres, l'utilisation d'indicateurs ichtyologiques. Un projet du programme national Liteau 2 du Ministère en charge de l'Environnement vise notamment à développer des indicateurs « poissons » pour ce suivi. Dans ce cadre un inventaire ichtyologique standardisé est en cours de réalisation sur une large gamme de MET en France. A partir des données ichtyologiques issues de cet inventaire, plusieurs métriques représentatives de la fonction de nourricerie des MET ont été définies ; elles sont basées sur une approche multispécifique via l'utilisation de guildes écologiques. Ensuite, la sensibilité de ces métriques au protocole de récolte des données ainsi qu'à des facteurs environnementaux a été évaluée. D'autre part, des indicateurs de contamination chimique des MET ont été développés. Enfin, des modèles pressions / impacts ont été réalisés pour déterminer l'effet des pressions anthropiques sur la fonction de nourricerie des MET. Ce travail montre qu'avec un protocole standardisé d'inventaires ichtyologiques, une bonne couverture spatiale et la prise en compte de facteurs environnementaux, il est possible de mettre en évidence les effets négatifs conséquents de certains contaminants sur la fonction de nourricerie des estuaires. Ces contaminants provoquent la diminution de l'abondance et du nombre d'espèces de juvéniles qui utilisent les estuaires comme nourricerie. Finalement, une méthodologie pour définir des normes et des points de référence a été développée afin de créer des indicateurs ichtyologiques liés à la fonction de nourricerie des MET qui soient opérationnels dans le cadre de la DCE.

International audience; We used primary productivity data derived from remote sensing images and catch data for the period 1998 to 2004 to characterize the productivity of eco-regions in the northeast Atlantic, Mediterranean, Black and Baltic Seas, and then analyzed the strength of the trophic linkage between primary productivity and marine fisheries production in European seas. Mean annual primary production (PP) derived from an ocean-color based model was highly contrasted among eco-regions, exceeding 500 g C m(-2) yr(-1) in the Marmara and North Seas but being less than 150 g C m(-2) yr(-1) in the Faroes, Adriatic-Ionian and Aegean-Levantine Seas. Fisheries production expressed in mean annual yield and primary production required to support catches (PPR) varied greatly among eco-regions, from 0.02 t km(-2) and 0.7 g C m(-2) yr(-1) for the oceanic northeast Atlantic eco-region to 6 t km(-2) and 130 g C m(-2) yr(-1) in the Marmara Sea respectively. Linear regression models showed significant positive relationships between PP and yield as well as between PP and PPR, suggesting a strong linkage between marine productivity and fisheries production in European seas. Moreover, this bottom-up control appeared consistent over time: recent mean annual yield for the period 1998 to 2004 reflected the long-term yield averaged over the last 3 decades. We argue that such large-scale coupling is due to energy transfer along the food web (from phytoplankton to predators) through predation processes, primary productivity driving the production of living marine resources and their exploitation at the scale of eco-regions. Our findings have an important bearing for ecosystem approaches to fisheries, particularly for the estimation of the capacity of eco-regions with regard to sustainable exploitation. This is further relevant in a context of climate change, because variations in PP linked to global warming could strongly modify fisheries production in the future.

Several works have demonstrated trends in the distribution of fish species relative to global warming. This study investigated whether similar trends have occurred for selected flatfish species on the continental shelf of the Bay of Biscay. These species were used as indicators and changes in their populations were studied in a coastal nursery ground where flatfish juveniles are concentrated as well as on the entire shelf. Previous studies analysing changes in sea surface temperature for the continental shelf indicate that winter warming occurred in the 1980s and 1990s. Sixteen autumn cruises conducted since 1981 in the Bay of Vilaine nursery area and 11 autumn cruises since 1987 over the entire shelf provided data on a nearly annual basis for the abundance of benthic fish. The four most common flatfish species were selected and their occurrence and yearly abundance were analysed with regard to specific biogeographic ranges and climate change. Similar results were obtained for juveniles on a nursery scale and for all age groups on the entire shelf. Although sole (Solea solea) showed irregular yearly variations, northern winter spawners such as plaice (Pleuronectes platessa) and dab (Limanda limanda) exhibited significantly high abundance during the 1980s, followed by a continuing low level and ultimately zero catches. On the other hand, the wedge sole (Dicologoglossa cuneata), a southern summer spawner, showed an increasing trend in the late 1990s. Diversos trabajos han demostrado tendencias en la distribución de especies de peces relacionadas con el calentamiento global. Este estudio se investigó si han ocurrido tendencias similares en especies seleccionadas de peces planos en la plataforma continental del Golfo de Vizcaya. Esas especies fueron usadas como indicadores y los cambios en sus poblaciones fueron analizados tanto en un área costera de concentración de juveniles como en toda la plataforma. Estudios previos de los cambios en la temperatura superficial del mar en la plataforma continental, indican la ocurrencia de periodos de calentamiento de invierno en los años 1980s y 1990s. 16 campañas de otoño realizadas desde 1981 en el área de crecimiento de la Bahía de Vilaine y 11 campañas de otoño efectuadas desde 1987 en toda la plataforma continental proporcionaron datos en una base casi anual de la abundancia de peces bentónicos. Se seleccionaron las cuatro especies de peces planos más comunes y su presencia y abundancia anual fueron analizadas con respecto a sus rangos biogeográficos específicos y al cambio climático. Se obtuvieron resultados similares para los juveniles en su área de crecimiento y para todos los grupos de edad a escala de toda la plataforma continental. Aunque el lenguado (Solea solea) mostró variaciones anuales irregulares, la solla (Pleuronectes platessa) y la limanda (Limanda limanda) que se reproducen en invierno mostraron una abundancia significativamente más alta durante los 1980s, seguida de una disminución continua y por último capturas nulas. Por el contrario, el lenguadillo (Dicologoglossa cuneata), que se reproduce en el sur durante el verano, mostró una tendencia al incremento a finales de los 1990s.

International audience; Indicators of growth and condition were used to compare the habitat quality of nurseries of juvenile sole (Solea solea L.) in the Bay of Biscay, based on one survey in 2000. The four biological indicators are poorly correlated with each other, suggesting that no single measure may give an adequate description of fish health and of its habitat's quality. Growth indicators showed significant differences between northern and southern areas. Juveniles from the two southernmost nurseries, the Gironde estuary and the Pertuis Antioche, displayed significant lower otolith increment widths and mean sizes. These differences were inversely related to water temperature and unrelated to genetic or age differences, and are unlikely to be due to limiting trophic conditions in the nurseries. Hence, they may be considered in terms of differences in habitat quality and potential anthropogenic impacts. Condition indices do not show this north-south pattern but highlight low condition values in the Pertuis Antioche. Shortterm and fluctuating biochemical indicators such as RNA/DNA ratios appeared to be unreliable over a long-term study, while morphometric indices seemed to be relevant, complementary indicators as they integrate the whole juvenile life-history of sole in the nurseries. The growth and condition indices of juveniles in September 2000 from nursery grounds exposed to the Erika oil spill in December 1999 were relatively high. These results lead us to suggest that there was no obvious impact of this event on the health of juvenile sole and on the quality of the exposed nursery grounds a few months after the event.

Indicators of growth and condition were used to compare the habitat quality of nurseries of juvenile sole (Solea solea L.) in the Bay of Biscay, based on one survey in 2000. The four biological indicators are poorly correlated with each other, suggesting that no single measure may give an adequate description of fish health and of its habitat’s quality. Growth indicators showed significant differences between northern and southern areas. Juveniles from the two southernmost nurseries, the Gironde estuary and the Pertuis Antioche, displayed significant lower otolith increment widths and mean sizes. These differences were inversely related to water temperature and unrelated to genetic or age differences, and are unlikely to be due to limiting trophic conditions in the nurseries. Hence, they may be considered in terms of differences in habitat quality and potential anthropogenic impacts. Condition indices do not show this north-south pattern but highlight low condition values in the Pertuis Antioche. Short-term and fluctuating biochemical indicators such as RNA/DNA ratios appeared to be unreliable over a long-term study, while morphometric indices seemed to be relevant, complementary indicators as they integrate the whole juvenile life-history of sole in the nurseries. The growth and condition indices of juveniles in September 2000 from nursery grounds exposed to the Erika oil spill in December 1999 were relatively high. These results lead us to suggest that there was no obvious impact of this event on the health of juvenile sole and on the quality of the exposed nursery grounds a few months after the event. Se usaron indicadores de crecimiento y condición de lenguados juveniles (Solea solea L.) para comparar la calidad del hábitat de áreas de cría en el Golfo de Vizcaya basados en un muestreo de 2000. Los cuatro indicadores biológicos mostraron bajas correlaciones entre sí, lo que sugiere que no existe una medida única para describir adecuadamente el estado de los peces y la calidad de su hábitat. Los indicadores de crecimiento mostraron diferencias significativas entre las áreas septentrionales y meridionales. Los juveniles de las áreas situadas más al sur: el estuario del Garona y Pertuis Antioche mostraron incrementos de otolitos y tamaños medios significativamente inferiores. Estas diferencias están inversamente relacionadas con la temperatura del agua, pero no con diferencias genéticas o de edad, y no es probable que se deba a una condición trófica limitante en las áreas de cría. Por tanto, pueden considerarse en términos de calidad del hábitat y el potencial impacto antropogénico. Los índices de condición no muestras este patrón norte-sur sino que destacan los bajos valores de condición en Pertuis Antioche. Los indicadores bioquímicos variables de corto término como las relaciones RNA/DNA no parecieron fiables para estudios de mayor escala, mientras que los índices morfométricos parecen ser relevantes y complementarios ya que integran toda el período juvenil de la vida de los lenguados en sus áreas de cría. Los valores de crecimiento y condición de juveniles en septiembre de 2000 en áreas de cría expuestas al vertido de crudo del Erika en diciembre de 1999 fueron relativamente elevadas. Estos resultados sugieren que no hubo un impacto obvio de este evento sobre la salud de los juveniles de lenguado ni en la calidad de las áreas de cría expuestas transcurridos unos pocos meses después del vertido.

We present a method for combining individual indicator results into a comprehensive diagnostic of fishing impacts on fish populations and communities. A conceptual framework for interpreting combined trends in a set of simple indicators is proposed, relying beforehand on qualitative expectations anchored in ecological theory. The initial state of the community is first assessed using published information. Which combinations of trends are acceptable or undesirable is decided, depending on the initial status. The indicators are then calculated from a time-series and their time trends are estimated as the slopes of linear models. Finally, the test results are combined within the predefined framework, providing a diagnostic on the dynamics of fishing impacts on populations and communities. The method is demonstrated for nine coastal and shelf-sea fish communities monitored by French surveys. Most communities were persistently or increasingly impacted by fishing. In addition, climate change seems to have contributed to changes in East Atlantic communities., Cet article propose une méthode utilisant des indicateurs pour élaborer un diagnostic sur les effets de la pêche sur les populations et les peuplements de poissons. Un cadre conceptuel permet d'interpréter les tendances conjointes d'indicateurs à partir de la théorie écologique. L'état initial du peuplement est d'abord évalué sur la base d'informations publiées. En fonction de l'état initial et des objectifs de gestion, les combinaisons des tendances sont qualifiées d'indésirables ou satisfaisantes. Les indicateurs sont ensuite estimés à partir de données de campagnes de pêches scientifiques: abondance et longueur moyenne d'une sélection de populations, nombre, biomasse totale, poids moyen et longueur moyenne dans le peuplement, et la pente du spectre de taille multispécifique. Les tendances temporelles de ces indicateurs sont testées au moyen d'un modèle linéaire, et les résultats des tests sont combinés en un diagnostic final. La méthode est mise en oeuvre pour neuf peuplements de poissons côtiers et du plateau continental, suivis par des campagnes françaises. Il en résulte que la plupart de ces peuplements sont affectés par la pêche de manière stationnaire ou croissante. Par ailleurs, les changements climatiques dans l'Atlantique Nord-Est contribuent aussi à des modifications dans les peuplements de poissons de cette région.

International audience; Outlines: description of estuary environment - standardisation of fish species richness - identification of main abiotic trends - effects of abiotic factors on fish species richness.