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Auteur Bach, P.; Gaertner, D.; Menkes, C.; Romanov, E.; Travassos, P.
Titre Effects of the gear deployment strategy and current shear on pelagic longline shoaling Type Article scientifique
Année 2009 Publication (up) Revue Abrégée Fish Res.
Volume 95 Numéro Pages 55-64
Mots-Clés Generalized additive model (GAM); Generalized linear model (GLM); maximum fishing depth; monofilament pelagic longline; sag ratio; temperature-depth recorders
Résumé Historical longline catch per unit effort (CPUE) constitutes the major time series used in tuna stock assessment to followthe trend in abundance since the beginning of the large-scale tuna fisheries. The efficiency and species composition of a longline fishing operations essentially depends on the overlap in the vertical and spatial distribution between hooks and species habitat. Longline catchability depends on the vertical distribution of hooks and the aim of our paper was to analyse principal factors affecting the deviation of observed longline hook depths from predicted values. Since observed hook depth is usually shallower than predicted, this deviation is called longline shoaling.We evaluate the accuracy of hook depth distribution estimated from a theoretical catenary model commonly used in longline CPUE standardizations. Temperature-depth recorders (TDRs) were deployed on baskets of a monitored longline. Mainline shapes and maximum fishing depths were similar to gear configurations commonly used to target both yellowfin and bigeye tuna by commercial longliners in the central part of the South Pacific Ocean. Our working hypothesis assumes that the maximum fishing depth reached by the mainline depends on the gear configuration (sag ratio, mainline length per basket), the fishing tactics (bearing of the setting) and environmental variables characterizing water mass dynamics (wind stress, current velocity and shear). Based on generalized additive models (GAMs) simple transformations are proposed to account for the non-linearity between the shoaling and explanatory variables. Then, generalized linear models (GLMs) were fit to model the effects of explanatory variables on the longline shoaling. Results indicated that the shoaling (absolute aswell as relative) was significantly influenced by (1) the shape of the mainline (i.e., the tangential angle), which is the strongest predictor, and (2) the current shear and the direction of setting. Geometric forcing (i.e. transverse versus in-line) between the environment and the longline set is shown for the first time from in situ experimental fishing data. Results suggest that a catenary model that does not take these factors into consideration provides a biased estimate of the vertical distribution of hooks and must be used with caution in CPUEs standardization methods. Since catchability varies in time and space we discuss how suitable data could be routinely collected onboard commercial fishing vessels in order to estimate longline catchability for stock assessments.

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ISSN 0165-7836 ISBN Médium
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Auteur Torres-Irineo, E.; Dreyfus-Leon, M.; Gaertner, D.; Salas, S.; Marchal, P.
Titre Adaptive responses of tropical tuna purse-seiners under temporal regulations Type Article scientifique
Année 2017 Publication (up) Revue Abrégée Ambio
Volume 46 Numéro 1 Pages 88-97
Mots-Clés atlantic; behavior; Closed season; eastern pacific-ocean; eastern tropical pacific; Fisher behaviour; Fisheries management; fishing strategies; fleet dynamics; mixed fisheries; model; Purse-seine fishing; state; trawlers; Tropical tuna
Résumé The failure to achieve fisheries management objectives has been broadly discussed in international meetings. Measuring the effects of fishery regulations is difficult due to the lack of detailed information. The yellowfin tuna fishery in the eastern Pacific Ocean offers an opportunity to evaluate the fishers' responses to temporal regulations. We used data from observers on-board Mexican purse-seine fleet, which is the main fleet fishing on dolphin-associated tuna schools. In 2002, the Inter-American Tropical Tuna Commission implemented a closed season to reduce fishing effort for this fishery. For the period 1992-2008, we analysed three fishery indicators using generalized estimating equations to evaluate the fishers' response to the closure. We found that purse-seiners decreased their time spent in port, increased their fishing sets, and maintained their proportion of successful fishing sets. Our results highlight the relevance of accounting for the fisher behaviour to understand fisheries dynamics when establishing management regulations.
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ISSN 0044-7447 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2072
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Auteur Milner-Gulland, E.J.; Garcia, S.; Arlidge, W.; Bull, J.; Charles, A.; Dagorn, L.; Fordham, S.; Zivin, J.G.; Hall, M.; Shrader, J.; Vestergaard, N.; Wilcox, C.; Squires, D.
Titre Translating the terrestrial mitigation hierarchy to marine megafauna by-catch Type Article scientifique
Année 2018 Publication (up) Revue Abrégée Fish. Fish.
Volume 19 Numéro 3 Pages 547-561
Mots-Clés albatrosses; artisanal fisheries; biodiversity offsets; biodiversity offsetting; circle hooks; conservation; economic incentives; fisheries bycatch; fishing effort; harbor porpoise; leatherback turtle; no net loss; seabird bycatch; sharks and rays; turtles
Résumé In terrestrial and coastal systems, the mitigation hierarchy is widely and increasingly used to guide actions to ensure that no net loss of biodiversity ensues from development. We develop a conceptual model which applies this approach to the mitigation of marine megafauna by-catch in fisheries, going from defining an overarching goal with an associated quantitative target, through avoidance, minimization, remediation to offsetting. We demonstrate the framework's utility as a tool for structuring thinking and exposing uncertainties. We draw comparisons between debates ongoing in terrestrial situations and in by-catch mitigation, to show how insights from each could inform the other; these are the hierarchical nature of mitigation, out-of-kind offsets, research as an offset, incentivizing implementation of mitigation measures, societal limits and uncertainty. We explore how economic incentives could be used throughout the hierarchy to improve the achievement of by-catch goals. We conclude by highlighting the importance of clear agreed goals, of thinking beyond single species and individual jurisdictions to account for complex interactions and policy leakage, of taking uncertainty explicitly into account and of thinking creatively about approaches to by-catch mitigation in order to improve outcomes for conservation and fishers. We suggest that the framework set out here could be helpful in supporting efforts to improve by-catch mitigation efforts and highlight the need for a full empirical application to substantiate this.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1467-2960 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2337
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Auteur Blanchard, J.L.; Coll, M.; Trenkel, V.M.; Vergnon, R.; Yemane, D.; Jouffre, D.; Link, J.S.; Shin, Y.-J.
Titre Trend analysis of indicators : a comparison of recent changes in the status of marine ecosystems around the world Type Article scientifique
Année 2010 Publication (up) Revue Abrégée Ices Journal of Marine Science
Volume 67 Numéro 4 Pages 732-744
Mots-Clés community; ecological indicators; ecosystem-based fisheries management; ecosystem effects of fishing; natural resource management
Résumé Blanchard, J. L., Coll, M., Trenkel, V. M., Vergnon, R., Yemane, D., Jouffre, D., Link, J. S., and Shin, Y-J. 2010. Trend analysis of indicators: a comparison of recent changes in the status of marine ecosystems around the world. – ICES Journal of Marine Science, 67: 732-744.
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ISSN 1054-3139 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 58
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Auteur Chassot, E.; Bonhommeau, S.; Dulvy, N.K.; Melin, F.; Watson, R.; Gascuel, D.; Pape, O.L.
Titre Global marine primary production constrains fisheries catches Type Article scientifique
Année 2010 Publication (up) Revue Abrégée Ecology Letters
Volume 13 Numéro Pages 495-505
Mots-Clés bottom-up; ecosystem; Fishing; Large; marine; quantile; regression; sustainable
Résumé 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.
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Volume de collection Numéro de collection Edition
ISSN 1461-023x ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 61
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