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Auteur Govinden, R.; Jauhary, R.; Filmalter, J.; Forget, F.; Soria, M.; Adam, S.; Dagorn, L.
Titre Movement Behaviour of Skipjack (Katsuwonus Pelamis) and Yellowfin (Thunnus Albacares) Tuna at Anchored Fish Aggregating Devices (FADs) in the Maldives, Investigated by Acoustic Telemetry Type Article scientifique
Année 2012 Publication Revue Abrégée Aquatic Living Resources
Volume FirstView Numéro Pages
Mots-Clés Behaviour; Fish Aggregating Devices; Indian Ocean; Passive acoustic telemetry; skipjack tuna; Yellowfin tuna
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Numéro d'Appel LL @ pixluser @ collection 193
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Auteur Nikolic, N.; Jérôme, M.; Fonteneau, A.; Evano, H.; Verrez-Bagnis, V.
Titre Identification of skipjack tuna juveniles based on DNA control region sequences and potential spawning area around reunion island Type Article scientifique
Année 2016 Publication Revue Abrégée Environmental Biology of Fishes
Volume 99 Numéro 2 Pages 171-178
Mots-Clés Age; dna; juvenile; Reunion island; skipjack tuna
Résumé In this study, we confirmed that DNA control region can be used to identify potential spawning area from pelagic juveniles species. We used the mitochondrial DNA control region to identify tuna juveniles predated by common dolphinfish and sampled in surface waters around Reunion Island. These were skipjack juveniles at an early stage (small length and young age). The biological results confirmed the species identification based on DNA analysis. Catch data by longline reveal a higher number of skipjack from October to December around Reunion Island corresponding to the period of our skipjack juvenile sampling
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ISSN 0378-1909 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1518
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Auteur Robert, M.; Dagorn, L.; Lopez, J.; Moreno, G.; Deneubourg, J.L.
Titre Does social behavior influence the dynamics of aggregations formed by tropical tunas around floating objects ? An experimental approach Type Article scientifique
Année 2013 Publication Revue Abrégée Journal of Experimental Marine Biology and Ecology
Volume 440 Numéro Pages 238-243
Mots-Clés Aggregation; Binary choice; FADs; Social behavior; tuna
Résumé Tropical tunas associate with objects floating at the surface of the ocean, a behavior widely exploited by fishers. However, the respective roles played by environmental variables and behavioral processes (e.g., social behavior) in the formation of these aggregations remain elusive. To investigate the role of social behavior in the dynamics of such aggregations, we used the binary choice approach. The experimental design comprised two close and identical anchored fish aggregating devices (FADS) equipped with an echo sounder buoy to monitor the aggregated biomass of tuna under each device. Analysis of the results entailed characterizing whether the aggregated biomass is distributed asymmetrically (indicative of social behavior playing a role in the dynamics) or symmetrically between the two close and identical FADs, and comparing the results with theoretical distributions based on different definitions of basic units (individual fish or small schools). The results suggest that social interactions underlie aggregation processes, which represents a major advance in our understanding of these aggregations, a priority for science-based fishery management. While recognizing the logistical and technical constraints, we encourage the development of experimental studies (e.g., in which animals are presented with controlled situations) to enhance our understanding of the behavior of large pelagic fish.
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ISSN 0022-0981 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 249
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Auteur Baidai, Y.; Dagorn, L.; Amande, M.J.; Gaertner, D.; Capello, M.
Titre Machine learning for characterizing tropical tuna aggregations under Drifting Fish Aggregating Devices (DFADs) from commercial echosounder buoys data Type Article scientifique
Année 2020 Publication Revue Abrégée Fish Res.
Volume 229 Numéro Pages 105613
Mots-Clés behavior; classification; communities; Direct abundance indicator; echo-sounder buoys; Echosounder buoys; estimate biomass; fads; Fish aggregating devices; Purse seiner; purse seiners; target strength; temperature; Tropical tunas; yellowfin thunnus-albacares
Résumé The use of echosounder buoys deployed in conjunction with Drifting Fish Aggregating Devices (DFADs) has progressively increased in the tropical tuna purse seine fishery since 2010 as a means of improving fishing efficiency. Given the broad distribution of DFADs, the acoustic data provided by echosounder buoys can provide an alternative to the conventional CPUE index for deriving trends on tropical tuna stocks. This study aims to derive reliable indices of presence of tunas (and abundance) using echosounder buoy data. A novel methodology is presented which utilizes random forest classification to translate the acoustic backscatter from the buoys into metrics of tuna presence and abundance. Training datasets were constructed by cross-referencing acoustic data with logbook and observer data which reported activities on DFADs (tuna catches, new deployments and visits of DFADs) in the Atlantic and Indian Oceans from 2013 to 2018. The analysis showed accuracies of 75 and 85 % for the recognition of the presence/absence of tuna aggregations under DFADs in the Atlantic and Indian Oceans, respectively. The acoustic data recorded at ocean-specific depths (6-45m in the Atlantic and 30-150m in the Indian Ocean) and periods (4 a.m.-4 p.m.) were identified by the algorithm as the most important explanatory variables for detecting the presence of tuna. The classification of size categories of tuna aggregations showed a global accuracy of nearly 50 % for both oceans. This study constitutes a milestone towards the use of echosounder buoys data for scientific purposes, including the development of promising fisheries-independent indices of abundance for tropical tunas.
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ISSN 0165-7836 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2816
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Auteur Poisson, F.; Abascal Crespo, F.; Ellis, J.R.; Chavance, P.; Pascal, B.; Santos, M.N.; Seret, B.; Korta, M.; Coelho, R.; Ariz, J.; Murua, H.
Titre Technical mitigation measures for sharks and rays in fisheries for tuna and tuna-like species: turning possibility into reality Type Article scientifique
Année 2016 Publication Revue Abrégée Aquat. Living Resour.
Volume 29 Numéro 4 Pages 402
Mots-Clés at-vessel mortality; Bycatch; california recreational fishery; circle hooks; eastern pacific-ocean; Elasmobranch; great-barrier-reef; j-hook performance; Mitigation; mortality; pelagic; pelagic longline fishery; postrelease survival; Purse seine fishery; rare-earth-metal; tuna regional fishery management organizations
Résumé Tuna fisheries have been identified as one of the major threats to populations of other marine vertebrates, including sea turtles, sharks, seabirds and marine mammals. The development of technical mitigation measures (MM) in fisheries is part of the code of conduct for responsible fisheries. An in-depth analysis of the available literature regarding bycatch mitigation in tuna fisheries with special reference to elasmobranchs was undertaken. Studies highlighting promising MMs were reviewed for four tuna fisheries (longline, purse seine, driftnets and gillnet, and rod and line – including recreational fisheries). The advantages and disadvantages of different MMs are discussed and assessed based on current scientific knowledge. Current management measures for sharks and rays in tuna Regional Fishery Management Organizations (t-RFMOs) are presented. A review of relevant studies examining at-vessel and postrelease mortality of elasmobranch bycatch is provided. This review aims to help fisheries managers identify pragmatic solutions to reduce mortality on pelagic elasmobranchs (and other higher vertebrates) whilst minimizing impacts on catches of target tuna species. Recent research efforts have identified several effective MMs that, if endorsed by t-RFMOs, could reduce elasmobranchs mortality rate in international tropical purse seine tuna fisheries. In the case of longline fisheries, the number of operational effective MMs is very limited. Fisheries deploying driftnets in pelagic ecosystems are suspected to have a high elasmobranchs bycatch and their discard survival is uncertain, but no effective MMs have been field validated for these fisheries. The precautionary bans of such gear by the EU and by some t-RFMOs seem therefore appropriate. Recreational tuna fisheries should be accompanied by science-based support to reduce potential negative impacts on shark populations. Priorities for research and management are identified and discussed.
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ISSN 0990-7440 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2056
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