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Auteur Travassos Tolotti, M.; Filmalter, J.D.; Bach, P.; Travassos, P.; Seret, B.; Dagorn, L.
Titre Banning is not enough: The complexities of oceanic shark management by tuna regional fisheries management organizations Type Article scientifique
Année 2015 Publication Revue Abrégée Global Ecology and Conservation
Volume 4 Numéro (up) Pages 1-7
Mots-Clés Bycatch; conservation; Fin trade; Pelagic shark; Tuna fisheries
Résumé Recently, declining populations of several pelagic shark species have led to global conservation concerns surrounding this group. As a result, a series of species-specific banning measures have been implemented by Regional Fishery Management Organizations (RFMOs) in charge of tuna fisheries, which include retention bans, finning bans and trading bans. There are both positive and negative aspects to most management measures, but generally, the positive aspects outweigh the negatives, ensuring the measure is beneficial to the resource and its users in the long term. Banning measures are a good first step towards the conservation of pelagic shark species, especially since they improve conservation awareness among fishers, managers and the public. Measures that impose total bans, however, can lead to negative impacts that may jeopardize the populations they were intended to protect. The majority of pelagic shark catches are incidental and most sharks die before they reach the vessel or after they are released. The legislation set out by RFMOs only prevents retention but not the actual capture or the mortality that may occur as a result. Managers should be fully aware that the development and implementation of mitigation measures are critical for a more effective conservation strategy.
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ISSN 2351-9894 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1498
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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 Revue Abrégée Ambio
Volume 46 Numéro (up) 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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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0044-7447 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2072
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Auteur Pons, M.; Branch, T.A.; Melnychuk, M.C.; Jensen, O.P.; Brodziak, J.; Fromentin, J.M.; Harley, S.J.; Haynie, A.C.; Kell, L.T.; Maunder, M.N.; Parma, A.M.; Restrepo, V.R.; Sharma, R.; Ahrens, R.; Hilborn, R.
Titre Effects of biological, economic and management factors on tuna and billfish stock status Type Article scientifique
Année 2017 Publication Revue Abrégée Fish Fish
Volume 18 Numéro (up) 1 Pages 1-21
Mots-Clés Fisheries management; marine conservation; stock assessment; stock status; Tuna fisheries
Résumé Commercial tunas and billfishes (swordfish, marlins and sailfish) provide considerable catches and income in both developed and developing countries. These stocks vary in status from lightly exploited to rebuilding to severely depleted. Previous studies suggested that this variability could result from differences in life-history characteristics and economic incentives, but differences in exploitation histories and management measures also have a strong effect on current stock status. Although the status (biomass and fishing mortality rate) of major tuna and billfish stocks is well documented, the effect of these diverse factors on current stock status and the effect of management measures in rebuilding stocks have not been analysed at the global level. Here, we show that, particularly for tunas, stocks were more depleted if they had high commercial value, were long-lived species, had small pre-fishing biomass and were subject to intense fishing pressure for a long time. In addition, implementing and enforcing total allowable catches (TACs) had the strongest positive influence on rebuilding overfished tuna and billfish stocks. Other control rules such as minimum size regulations or seasonal closures were also important in reducing fishing pressure, but stocks under TAC implementations showed the fastest increase of biomass. Lessons learned from this study can be applied in managing large industrial fisheries around the world. In particular, tuna regional fisheries management organizations should consider the relative effectiveness of management measures observed in this study for rebuilding depleted large pelagic stocks.
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Volume de collection Numéro de collection Edition
ISSN 1467-2979 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2079
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Auteur Sardenne, F.; Diaha, N.'G.C.; Amande, M.J.; Zudaire, I.; Couturier, L.I.E.; Metral, L.; Le Grand, F.; Bodin, N.
Titre Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean Type Article scientifique
Année 2019 Publication Revue Abrégée Can. J. Fish. Aquat. Sci.
Volume 76 Numéro (up) 1 Pages 69-80
Mots-Clés lipids; top predators; pacific-ocean; thunnus-albacares; stable-isotope analyses; western; vertical movements; bigeye tuna; vinciguerria-nimbaria; yellowfin tuna
Résumé In the Gulf of Guinea, bigeye tuna (Thunnus obesus; BET) and yellowfin tuna (Thunnus albacares; YFT) are an important part of commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes, we examined their trophic niche partitioning in this understudied region. Trophic niche overlap was high (> 70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high delta N-15 values and high proportions of monounsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (delta N-15 values decreased by similar to 0.5 parts per thousand), suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatom marker 20:5(n-3) increased in the seasonal upwelling area, highlighting the influence of seasonal habitat on the diet of tuna. The relatively lipid-rich muscle (similar to 6% dry mass) of Atlantic tropical tuna suggests a richer diet in this region than that of Indian Ocean tropical tuna and (or) differences in energy allocation strategies.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0706-652x ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2483
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Auteur Young, J.W.; Olson, R.J.; Ménard, F.; Kuhnert, P.M.; Duffy, L.M.; Allain, V.; Logan, J.M.; Lorrain, A.; Somes, C.J.; Graham, B.; Goñi, N.; Pethybridge, H.; Simier, M.; Potier, M.; Romanov, E.; Pagendam, D.; Hannides, C.; Choy, C.A.
Titre Setting the stage for a global-scale trophic analysis of marine top predators: a multi-workshop review Type Article scientifique
Année 2015 Publication Revue Abrégée Rev Fish Biol Fisheries
Volume 25 Numéro (up) 1 Pages 261-272
Mots-Clés climate change; Freshwater & Marine Ecology; Global diet data; Global nitrogen model; Global stable isotope data; Predictive analyses; top predators; Tuna trophic ecology; Zoology
Résumé Global-scale studies of marine food webs are rare, despite their necessity for examining and understanding ecosystem level effects of climate variability. Here we review the progress of an international collaboration that compiled regional diet datasets of multiple top predator fishes from the Indian, Pacific and Atlantic Oceans and developed new statistical methods that can be used to obtain a comprehensive ocean-scale understanding of food webs and climate impacts on marine top predators. We loosely define top predators not as species at the apex of the food web, but rather a guild of large predators near the top of the food web. Specifically, we present a framework for world-wide compilation and analysis of global stomach-contents and stable-isotope data of tunas and other large pelagic predatory fishes. To illustrate the utility of the statistical methods, we show an example using yellowfin tuna in a “test” area in the Pacific Ocean. Stomach-contents data were analyzed using a modified (bagged) classification tree approach, which is being prepared as an R statistical software package. Bulk δ15N values of yellowfin tuna muscle tissue were examined using a Generalized Additive Model, after adjusting for spatial differences in the δ15N values of the baseline primary producers predicted by a global coupled ocean circulation-biogeochemical-isotope model. Both techniques in tandem demonstrated the capacity of this approach to elucidate spatial patterns of variations in both forage species and predator trophic positions and have the potential to predict responses to climate change. We believe this methodology could be extended to all marine top predators. Our results emphasize the necessity for quantitative investigations of global-scale datasets when evaluating changes to the food webs underpinning top ocean predators under long-term climatic variability.
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ISSN 0960-3166, 1573-5184 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1263
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