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Auteur Coll, M.; Steenbeek, J.; Sole, J.; Palomera, I.; Christensen, V.
Titre (up) Modelling the cumulative spatial-temporal effects of environmental drivers and fishing in a NW Mediterranean marine ecosystem Type Article scientifique
Année 2016 Publication Revue Abrégée Ecol. Model.
Volume 331 Numéro Pages 100-114
Mots-Clés acoustic estimation; anchovy engraulis-encrasicolus; climate-change; Cumulative effects; Ecopath with Ecosim; environment; european hake; exploited ecosystems; fishing; food-web model; food webs; hake merluccius-merluccius; protected areas; south catalan sea; trawling disturbance
Résumé To realistically predict spatial-temporal dynamics of species in marine ecosystems it is essential to consider environmental conditions in conjunction with human activities and food web dynamics. In this study, we used Ecospace, the spatial-temporal dynamic module of Ecopath with Ecosim (EwE) food web model, to drive a spatially explicit marine food web model representing the Southern Catalan Sea (NW Mediterranean) with various environmental drivers and with fishing. We then evaluated the individual and joint effects of environmental conditions and fishing in various compartments of the food web. First we used a previously developed EwE model fitted to time series of data from 1978 to 2010 as a baseline configuration. The model included 40 functional groups and four fishing fleets. We first ran the original Ecospace spatial-temporal dynamic model using the original habitat configuration, in addition to fishing, and we predicted species distributions and abundances. Afterwards, we ran the new habitat foraging capacity model using the most important environmental drivers linked with the Ebro River delta dynamics (salinity, temperature, and primary production), in addition to depth, substrate and fishing, and we compared results with those from the original implementation of Ecospace. Three commercial species, European hake (Merluccius merluccius), anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus), were used to analyse results. Species distributions more closely matched the empirical information available from the study area when using the new habitat capacity model. Results suggested that the historical impacts of fishing and environmental conditions on the biomass and distributions of hake, anchovy and sardine were not additive, but mainly cumulative with a synergistic or antagonistic effect. Fishing had the highest impact on spatial modelling results while the spatial distribution of primary producers and depth followed in importance. This study contributes to the development of more reliable predictions of regional change in marine ecosystems of the Mediterranean Sea. (C) 2016 Elsevier B.V. All rights reserved.
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ISSN 0304-3800 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 1643
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Auteur Joo, R.; Bertrand, S.; Chaigneau, A.; Niquen, M.
Titre (up) Optimization of an artificial neural network for identifying fishing set positions from VMS data : an example from the Peruvian anchovy purse seine fishery Type Article scientifique
Année 2011 Publication Revue Abrégée Ecological Modelling
Volume 222 Numéro Pages 1048-1059
Mots-Clés analysis; anchovy; Artificial; fishery; Fishing; locations; Monitoring; networks; neural; purse; seine; Sensitivity; set; System; Vessel
Résumé The spatial behavior of numerous fishing fleets is nowadays well documented thanks to satellite Vessel Monitoring Systems (VMS). Vessel positions are recorded on a frequent and regular basis which opens promising perspectives for improving fishing effort estimation and management. However, no specific information is provided on whether the vessel is fishing or not. To answer that question, existing works on VMS data usually apply simple criteria (e.g. threshold on speed). Those simple criteria generally focus in detecting true positives (a true fishing set detected as a fishing set); conversely, estimation errors are given no attention. For our case study, the Peruvian anchovy fishery, those criteria overestimate the total number of fishing sets by 182%. To overcome this problem an artificial neural network (ANN) approach is presented here. In order to set both the optimal parameterization and use “rules” for this ANN, we perform an extensive sensitivity analysis on the optimization of (1) the internal structure and training algorithm of the ANN and (2) the “rules” used for choosing both the relative size and the composition of the databases (DBs) used for training and inferring with the ANN. The “optimized” ANN greatly improves the estimates of the number and location of fishing events. For our case study, ANN reduces the total estimation error on the number of fishing sets to 1% (in average) and obtains 76% of true positives. This spatially explicit information on effort, provided with error estimation, should greatly reduce misleading interpretations of catch per unit effort and thus significantly improve the adaptive management of fisheries. While fitted on Peruvian anchovy fishery data, this type of neural network approach has wider potential and could be implemented in any fishery relying on both VMS and at-sea observer data. In order to increase the accuracy of the ANN results, we also suggest some criteria for improving sampling design by at-sea observers and VMS data.
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Numéro d'Appel LL @ pixluser @ collection 147
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Auteur Foveau, A.; Vaz, S.; Desroy, N.; Kostylev, V.E.
Titre (up) Process-driven and biological characterisation and mapping of seabed habitats sensitive to trawling Type Article scientifique
Année 2017 Publication Revue Abrégée PLoS One
Volume 12 Numéro 10 Pages e0184486
Mots-Clés beam trawl; benthic communities; british-isles; continental-shelf; english-channel; fishing disturbance; impact; north-sea; scotian shelf; taxonomic sufficiency
Résumé The increase of anthropogenic pressures on the marine environment together with the necessity of a sustainable management of marine living resources have underlined the need to map and model coastal environments, particularly for the purposes of spatial planning and for the implementation of integrated ecosystem-based management approach. The present study compares outputs of a process-driven benthic habitat sensitivity (PDS) model to the structure, composition and distribution of benthic invertebrates in the Eastern English Channel and southern part of the North Sea. Trawl disturbance indicators (TDI) computed from species biological traits and benthic community composition were produced from samples collected with a bottom trawl. The TDI was found to be highly correlated to the PDS further validating the latter's purpose to identify natural process-driven pattern of sensitivity. PDS was found to reflect an environmental potential that may no longer be fully observable in the field and difference with in situ biological observations could be partially explained by the spatial distribution of fishery pressure on the seafloor. The management implication of these findings are discussed and we suggest that, used in conjunction with TDI approaches, PDS may help monitor management effort by evaluating the difference between the current state and the presumed optimal environmental status of marine benthic habitats.
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ISSN 1932-6203 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2202
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Auteur Fu, C.; Travers-Trolet, M.; Velez, L.; Grüss, A.; Bundy, A.; Shannon, L.J.; Fulton, E.A.; Akoglu, E.; Houle, J.E.; Coll, M.; Verley, P.; Heymans, J.J.; John, E.; Shin, Y.-J.
Titre (up) Risky business: The combined effects of fishing and changes in primary productivity on fish communities Type Article scientifique
Année 2018 Publication Revue Abrégée Ecological Modelling
Volume 368 Numéro Pages 265-276
Mots-Clés Combined effect; Fishing; Marine ecosystem; Meta-analysis; Multiple drivers; Synergism
Résumé There is an increasing need to understand community-level or whole-ecosystem responses to multiple stressors since the impacts of multiple stressors on marine systems depend not only on species-level responses, but also on species interactions and ecosystem structure. In this study, we used a multi-model ecosystem simulation approach to explore the combined effects of fishing and primary productivity on different components of the food-web across a suite of ecosystems and a range of model types. Simulations were carried out under different levels of primary productivity and various fishing scenarios (targeting different trophic levels). Previous work exploring the effects of multiple stressors often assumed that the combined effects of stressors are additive, synergistic or antagonistic. In this study, we included a fourth category “dampened”, which refers to less negative or to less positive impacts on a given ecosystem component compared to additive effects, and in contrast to previous studies, we explicitly considered the direction of the combined effects (positive or negative). We focused on two specific combined effects (negative synergism and positive dampened) associated with the ecological risk of resultant lower fish biomass than expected under additive effects. Through a meta-analysis of the multi-models’ simulation results, we found that (i) the risk of negative synergism was generally higher for low-trophic-level (LTL) taxa, implying that following an increase of fishing pressure on a given LTL stock, the subsequent decrease of biomass under low primary productivity would be higher than expected when fishing is the sole driver and (ii) the risk of positive dampened effects was generally higher for high-trophic-level (HTL) taxa, implying that given a management measure aimed at reducing the impact of fishing on HTL stocks, the subsequent rebuilding of these stocks would be slower than expected if only fishing were considered. Our approach to categorizing and exploring cumulative risk can be applied to evaluate other community properties and indicators and our findings could provide guidance in fisheries management.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2235
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Auteur Perry, R.I.; Cury, P.; Brander, K.; Jennings, S.; Mollmann, C.; Planque, B.
Titre (up) Sensitivity of marine systems to climate and fishing: Concepts, issues and management responses Type Article scientifique
Année 2010 Publication Revue Abrégée Journal of Marine Systems
Volume 79 Numéro Pages 427-435
Mots-Clés change; climate; Communities; ecosystems; fisheries; Fishing; management; Populations; variability
Résumé Modern fisheries research and management must understand and take account of the interactions between climate and fishing, rather than try to disentangle their effects and address each separately. These interactions are significant drivers of change in exploited marine systems and have ramifications for ecosystems and those who depend on the services they provide. We discuss how fishing and climate forcing interact on individual fish, marine populations, marine communities, and ecosystems to bring these levels into states that are more sensitive to (i.e. more strongly related with) climate forcing. Fishing is unlikely to alter the sensitivities of individual finfish and invertebrates to climate forcing. It will remove individuals with specific characteristics from the gene pool, thereby affecting structure and function at higher levels of organisation. Fishing leads to a loss of older age classes, spatial contraction, loss of sub-units, and alteration of life history traits in populations, making them more sensitive to climate variability at interannual to interdecadal scales. Fishing reduces the mean size of individuals and mean trophic level of communities, decreasing their turnover time leading them to track environmental variability more closely. Marine ecosystems under intense exploitation evolve towards stronger bottom-up control and greater sensitivity to climate forcing. Because climate change occurs slowly, its effects are not likely to have immediate impacts on marine systems but will be manifest as the accumulation of the interactions between fishing and climate variability – unless threshold limits are exceeded. Marine resource managers need to develop approaches which maintain the resilience of individuals, populations, communities and ecosystems to the combined and interacting effects of climate and fishing. Overall, a less-heavily fished marine system, and one which shifts the focus from individual species to functional groups and fish communities, is likely to provide more stable catches with climate variability and change than would a heavily fished system. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
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ISSN 0924-7963 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 95
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