The present survey examines the trophodynamics of a suite of 19 perfluoroalkyl substances (PFASs) in a temperate macrotidal estuary (Gironde, SW France). Across the 147 biota samples (18 taxa) collected, perfluorooctane sulfonate (PFOS), perfluorooctane sulfonamide (FOSA), and C-C perfluoroalkyl carboxylates (PFCAs) were the most-recurrent analytes. ΣPFASs ranged between 0.66-45 ng per g of wet weight of the whole body. Benthic organisms had relatively high ΣPFASs compared to demersal organisms and displayed specific composition profiles with higher relative abundances of C and C PFCAs. Trophic magnification factors (TMFs) were determined through the use of linear mixed effect models including censored data, thereby considering data below detection limits as well as the interspecific variability of δN and PFAS levels (random effects). TMFs were almost consistently >1 in the benthic food web as well as when considering all data pooled together, providing evidence for the biomagnification of several PFASs in estuarine environments. In addition, in contrast with previous observations, TMFs determined in the estuarine benthic web were found to significantly decrease with increasing chain length for C-C PFCAs and C-C perfluoroalkyl sulfonates. This suggests that PFAS chemical structure might not be necessarily predictive of TMFs, which are also influenced by the trophic web characteristics.

In order to provide reliable scientific advice and support for fisheries management, it is necessary to evaluate the biological and economic sustainability of complex fisheries, such as multi-species multifleet fisheries. Existing policy-screening modelling tools are not fully suitable in this purpose due to either an oversimplified description of population dynamics, or due to the lack of consideration of economic aspects. In this paper, we present a package that enables quantitative bioeconomic assessment of management scenarios. Population dynamics is described through spatially-and seasonally-explicit models. Exploitation dynamics is characterized by several fishing activities with specific spatial and seasonal features, and practiced by several kinds of vessels with specific technical characteristics. Exploitation costs and revenues are considered at several levels: the fishing trip, the fishing unit (vessel and crew), and the vessel owner. The model is generic and can be used for different types of fisheries. A database is attached to the software for the storage and updating of information for each fishery. This includes the specification of model dimensions and of the parameters describing populations and exploitation. Several model assumptions regarding either population or exploitation may be adapted to suit a specific fishery. Both policies and corresponding fishers' response may be interactively specified through JAVA™ scripts. This version of ISIS-Fish allows for the calculation of biological and economic consequences of a range of policies, including conventional ones like catch and effort controls, and alternative policies such as marine protected areas. To facilitate policyscreening in a high-dimension parameter space, the software includes features, like interfaces for sensitivity analysis and simulation queues.

Rougier, T., Lambert, P., Drouineau, H., Girardin, M., Castelnaud, G., Carry, L., Aprahamian, M., Rivot, E., and Rochard, E. 2012. Collapse of allis shad, Alosa alosa, in the Gironde system (southwest France): environmental change, fishing mortality, or Allee effect? – ICES Journal of Marine Science, 69: 1802–1811. At the end of the 20th century the allis shad population in the Gironde was the largest in Europe. During the first decade of the 21st century, catches declined dramatically by two orders of magnitude, and a fishery moratorium was implemented in 2008. This deterioration in the status of the stock was confirmed by three independent assessments (abundance of juveniles and of potential and effective spawners). Three hypotheses on the cause of the collapse were examined: (i) an environmental change in freshwater and/or in the estuary; (ii) an increase in marine and/or estuarine mortality; and (iii) the presence of an Allee effect. Changes in flow, temperature, and water quality over the period were inconclusive, but remain a possible causative factor. The instantaneous rate of marine (mean: 0.7 year−1, s.e. 0.1 year−1) and estuarine (mean: 2.6 year−1, s.e. 0.1 year−1) mortalities showed no trend between 1991 and 2003. Nevertheless, the past high estuarine (fishing) mortalities combined with a demographic Allee effect in the reproduction dynamics could explain the population collapse and hamper the stock recovery under the moratorium. This conclusion is, however, tentative as it was not possible to prove the presence of the density-dependent mechanism associated with the demographic Allee effect.

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-In this paper, we present an approach to compare the impact of different management options on the dynamics of a mixed fishery. We used ISIS-Fish, a simulation tool aimed at evaluating the impact of spatial and seasonal management measures on the dynamics of mixed fisheries. The French Nephrops norvegicus (Norway lobster) -Merluccius merluccius (hake) mixed fishery of the Bay of Biscay was chosen as a study case. First, we parameterised the population and exploitation models. We then selected several management measures, including marine protected areas (MPAs) and total allowable catches (TAC), and parameterised fishermen's reaction to each measure. Then, a sensitivity analysis was performed according to a fractional factorial experimental design. Management scenarios were assessed and compared using a statistical simulation design. The sensitivity analysis showed the large influence of some parameters, such as natural mortality, N. norvegicus fecundity, and catchability on both abundance and catches. Given model parameters, an improvement of trawl selectivity and several MPA designs (differing in size, seasonality and location) were found to result in a significant increase in abundance over 10 years, especially for N. norvegicus. This study illustrates the need for a pluri-specific approach to fisheries assessment and management. Key words:Fisheries dynamics / Spatial model / Management measures / Sensitivity analysis / Simulation design Résumé -Évaluation de l'effet de différents scénarios de gestion à l'aide du simulateur « ISIS-Fish » : la pêcherie mixte merlu-langoustine française du golfe de Gascogne. Dans cet article, nous présentons des mé-thodes destinées à comparer l'impact de différentes alternatives de gestion sur la dynamique d'une pêcherie mixte. Pour cela, nous avons utilisé un outil de simulation, « ISIS-Fish », conçu pour évaluer les effets de mesures de gestion spatiales et saisonnières. Nous avons choisi la pêcherie mixte de merlu -langoustine (Merluccius merluccius -Nephrops norvegicus) française du golfe de Gascogne comme exemple d'étude. Dans un premier temps, un paramétrage des modèles de population et d'exploitation a été réalisé. La réaction des pêcheurs face aux mesures de gestion sélectionnées, notamment aux aires marines protégées et aux captures totales admissibles (TAC), a ensuite été programmée. Dans un second temps, une analyse de sensibilité a été réalisée à l'aide d'un plan d'expériences factoriel fractionnaire. Enfin, un second plan de simulation a permis d'évaluer l'effet des différents scénarios de gestion. L'analyse de sensibilité a permis de mettre en évidence l'influence importante de certains paramètres, notamment la mortalité naturelle, la fé-condité de la langoustine et la capturabilité sur les captures et les abondances. Une amélioration de la sélectivité des chaluts et certaines aires marines protégées ont permis d'obtenir une augmentation significative des abondances sur une période de 10 ans, en particulier pour la langoustine. Cette étude a aussi mis en ...