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Auteur (up) Gasche, L.; Gascuel, D.; Shannon, L.; Shin, Y.-J.
Titre Global assessment of the fishing impacts on the Southern Benguela ecosystem using an EcoTroph modelling approach Type Article scientifique
Année 2012 Publication Revue Abrégée Journal of Marine Systems
Volume 90 Numéro 1 Pages 1-12
Mots-Clés Ecosystem indicators; EcoTroph; Fishing impact; Overfishing; southern Benguela; Trophic modelling
Résumé We show that the EcoTroph model based on trophic spectra is an efficient tool to build ecosystem diagnoses of the impact of fishing. Using the Southern Benguela case study as a pretext, we present the first thorough application of the model to a real ecosystem. We thus review the structure and functioning of EcoTroph and we introduce the user to the steps that should be followed, showing the various possibilities of the model while underlining the most critical points of the modelling process. We show that EcoTroph provides an overview of the current exploitation level and target factors at the ecosystem scale, using two distinct trophic spectra to quantify the fishing targets and the fishing impact per trophic level. Then, we simulate changes in the fishing mortality, facilitating differential responses of two groups of species within the Southern Benguela ecosystem to be distinguished. More generally, we highlight various trends in a number of indicators of the ecosystem's state when increasing fishing mortality and we show that this ecosystem is moderately exploited, although predatory species are at their MSY. Finally, trophic spectra of the fishing effort multipliers EMSY and E(0.1) are proposed as tools for monitoring the ecosystem effects of fishing.
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ISSN 0924-7963 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 190
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Auteur (up) Grüss, A.; Harford, W.J.; Schirripa, M.J.; Velez, L.; Sagarese, S.R.; Shin, Y.-J.; Verley, P.
Titre Management strategy evaluation using the individual-based, multispecies modeling approach OSMOSE Type Article scientifique
Année 2016 Publication Revue Abrégée Ecological Modelling
Volume 340 Numéro Pages 86-105
Mots-Clés Ecosystem modeling; end-to-end model; Gulf of Mexico; Management strategy evaluation; Risk of overfishing; Total acceptable catch
Résumé End-to-end ecosystem modeling platforms, including OSMOSE, are key tools for informing ecosystem-based fisheries management (EBFM). End-to-end models ideally implement two-way interactions between model components, yet two-way interactions between high trophic level (HTL) functional groups and humans (fisheries managers and fishers) are currently missing in OSMOSE. We developed a management strategy evaluation (MSE) framework for OSMOSE, which allows for feedback between HTL functional groups and fisheries managers. This framework couples OSMOSE to a management procedure integrating decision rules and accounting for scientific uncertainty and the acceptable risk of overfishing. We applied the MSE framework to the OSMOSE model of the West Florida Shelf, so as to conduct an evaluation of total allowable catch (TAC) strategies for red grouper (Epinephelus morio) in a context of episodic events of natural mortality. Our simulations indicate that TAC strategies that assume higher scientific uncertainty and/or lower acceptable risk of overfishing result in higher biomass-related metrics for red grouper. However, the levels of scientific uncertainty and acceptable risk of overfishing impose a trade-off between biomass-related and catch-related metrics for red grouper. Our simulations also indicate that updating red grouper TAC more frequently in a context of episodic events of natural mortality does not have a large impact on biomass-related and catch-related metrics for red grouper and other functional groups. The MSE we conducted for red grouper is strategic, and its outcomes, which were obtained under a specific set of assumptions, must be considered preliminary. We discuss how future research could help enhance understanding of the possible impacts of TAC strategies for red grouper. The MSE framework designed for OSMOSE links the dynamics of HTL functional groups to that of fisheries managers, thereby allowing OSMOSE to be better suited for informing EBFM. This framework is an invaluable asset in assessing the performance of fisheries management strategies, but could also be used for other purposes, such as the evaluation of research monitoring programs.
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Volume de collection Numéro de collection Edition
ISSN 0304-3800 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1615
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Auteur (up) Grüss, A.; Schirripa, M.J.; Chagaris, D.; Velez, L.; Shin, Y.-J.; Verley, P.; Oliveros-Ramos, R.; Ainsworth, C.H.
Titre Estimating natural mortality rates and simulating fishing scenarios for Gulf of Mexico red grouper (Epinephelus morio) using the ecosystem model OSMOSE-WFS Type Article scientifique
Année 2016 Publication Revue Abrégée Journal of Marine Systems
Volume 154, Part B Numéro Pages 264-279
Mots-Clés Fishing scenarios; Gulf of Mexico; Marine ecosystem modeling; Natural mortality; Red grouper; West Florida Shelf
Résumé The ecosystem model OSMOSE-WFS was employed to evaluate natural mortality rates and fishing scenarios for Gulf of Mexico (GOM) red grouper (Epinephelus morio). OSMOSE-WFS represents major high trophic level (HTL) groups of species of the West Florida Shelf, is forced by the biomass of plankton and benthos groups, and has a monthly time step. The present application of the model uses a recently developed ‘stochastic mortality algorithm’ to resolve the mortality processes of HTL groups. OSMOSE-WFS predictions suggest that the natural mortality rate of juveniles of GOM red grouper is high and essentially due to predation, while the bulk of the natural mortality of adult red grouper results from causes not represented in OSMOSE-WFS such as, presumably, red tides. These results were communicated to GOM red grouper stock assessments. Moreover, OSMOSE-WFS indicate that altering the fishing mortality of GOM red grouper may have no global impact on the biomass of the major prey of red grouper, due to the high complexity and high redundancy of the modeled system. By contrast, altering the fishing mortality of GOM red grouper may have a large impact on the biomass of its major competitors. Increasing the fishing mortality of red grouper would increase the biomass of major competitors, due to reduced competition for food. Conversely, decreasing the fishing mortality of red grouper would diminish the biomass of major competitors, due to increased predation pressure on the juveniles of the major competitors by red grouper. The fishing scenarios that we evaluated may have slightly different impacts in the real world, due to some discrepancies between the diets of red grouper and its major competitors predicted by OSMOSE-WFS and the observed ones. Modifications in OSMOSE-WFS are suggested to reduce these discrepancies.
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Editeur Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0924-7963 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1500
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Auteur (up) Halouani, G.; Gascuel, D.; Hattab, T.; Lasram, F.B.R.; Coll, M.; Tsagarakis, K.; Piroddi, C.; Romdhane, M.S.; Le Loc'h, F.
Titre Fishing impact in Mediterranean ecosystems: an EcoTroph modeling approach Type Article scientifique
Année 2015 Publication Revue Abrégée Journal of Marine Systems
Volume 150 Numéro Pages 22-33
Mots-Clés Ecosystem modeling; EcoTroph; Fishing impact; food web; Mediterranean Sea; Trophic levels; Trophic spectrum
Résumé The EcoTroph modeling approach was applied to five Mediterranean marine ecosystems to characterize their food webs and investigate their responses to several simulated fishing scenarios. First, EcoTroph was used to synthesize the outputs of five pre-existing heterogeneous Ecopath models in a common framework, and thus to compare different ecosystems through their trophic spectra of biomass, catch, and fishing mortalities. This approach contributes to our understanding of ecosystem functioning, from both ecological and fisheries perspectives. Then, we assessed the sensitivity of each ecosystem to fishery, using EcoTroph simulations. For the five ecosystems considered, we simulated the effects of increasing or decreasing fishing mortalities on both the biomass and the catch per trophic class. Our results emphasize that the Mediterranean Sea is strongly affected by the depletion of high trophic level organisms. Results also show that fisheries impacts, at the trophic level scale, differ between ecosystems according to their trophic structure and exploitation patterns. A top-down compensation effect is observed in some simulations where a fishing-induced decrease in the biomass of predators impacts their prey, leading to an increase in the biomass at lower trophic levels. The results of this comparative analysis highlight that ecosystems where top-down controls are observed are less sensitive to variations in fishing mortality in terms of total ecosystem biomass. This suggests that the magnitude of top-down control present in a system can affect its stability.
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Langue Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0924-7963 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1345
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Auteur (up) Helias, A.; Langlois, J.; Freon, P.
Titre Fisheries in life cycle assessment: Operational factors for biotic resources depletion Type Article scientifique
Année 2018 Publication Revue Abrégée Fish. Fish.
Volume 19 Numéro 6 Pages 951-963
Mots-Clés catch; catch series; characterization factor; fishing impact; global fisheries; impact assessment; impact assessment method; lca; surplus production model
Résumé Life cycle assessment (LCA) is the normed and international framework for assessing the environmental impacts of most human activities. LCA is commonly used to assess various aspects of fisheries but is only at the onset for estimating impacts of fish removal. This study proposes original characterization factors (CFs) to quantify impacts on biotic resources using the mass of fish caught. This mid-point assessment occurs in impact pathways leading to natural resources, one of the three areas of protection in LCA, and thus fisheries can be compared according to the depleted stock fraction. CFs are defined by the marginal approach applied to the Schaefer model, representing the dynamics of the stocks. They combine catches, current biomass and maximum intrinsic growth rates, determined from the application of the CMSY algorithm (Froese etal. (2017), Fish Fish, 18, 506) with FAO and FishBase data. A multistock CF is also proposed and used for multispecies-stocks. CFs for the 4,993 stocks defined from global FAO areas are obtained and sorted according to the robustness of the model hypotheses. CF values among stocks generally tend to decrease when fish catches increase because high catches are generally associated with abundant stocks. Multispecies-stocks CFs for the northeast Atlantic Ocean are compared to ICES-based CFs and are reliable for the main fished stocks. With this simple and generic structure, this operational fish resource depletion potential could be extended to other biotic resources.
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Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 1467-2960 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2445
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