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Auteur (up) Robinson, J.; Guillotreau, P.; Jimenez-Toribio, R.; Lantz, F.; Nadzon, L.; Dorizo, J.; Gerry, C.; Marsac, F.
Titre Impacts of climate variability on the tuna economy of Seychelles Type Article scientifique
Année 2010 Publication Revue Abrégée Climate Research
Volume 43 Numéro Pages 149-162
Mots-Clés climate; economy; Enso; fisheries; Seychelles; tuna; variability
Résumé Many small island states have developed economies that are strongly dependent on tuna fisheries. Consequently, they are vulnerable to the socio-economic effects of climate change and variability, processes that are known to impact tuna fisheries distribution and productivity. The aim of this study was to assess the impacts of climate oscillations on the tuna-dependent economy of Seychelles. Using a multiplier approach, the direct, indirect and induced economic effects of the tuna industry expenditure benefiting the Seychelles' economy declined in 1998 by 58, 26 and 35%, respectively (mean decline: 42%), a year of strong climate oscillation in the western Indian Ocean. Multivariate patterns in tuna purse-seine vessel expenditures in port were substantially modified by strong climate oscillations, particularly in 1998. A cointegration time-series model predicted that a 40% decline in tuna landings and transhipment in Port Victoria, a value commensurate with that observed in 1998, would result in a 34% loss for the local economy solely through reductions in cargo handling expenditures. Of several indices tested, the Indian Oscillation Index was best at predicting the probability of switching between low and high regimes of landings and transhipment, which translate into impacts for the economy. It is hypothesised that a late 2006/early 2007 climate oscillation was compounded by prior overfishing to produce a stronger impact on the fishery and economy of Seychelles. The effects of fishing and climate variability on tuna fisheries are complex and pose significant challenges for fisheries management and the economic development of countries in the Indian Ocean.
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ISSN 0936-577x ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 101
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Auteur (up) Rouyer, T.; Bonhommeau, S.; Giordano, N.; Ellul, S.; Ellul, G.; Deguara, S.; Wendling, B.; Belhaj, M.M.; Kerzerho, V.; Bernard, S.
Titre Tagging Atlantic bluefin tuna from a farming cage: An attempt to reduce handling times for large scale deployments Type Article scientifique
Année 2019 Publication Revue Abrégée Fisheries Research
Volume 211 Numéro Pages 27-31
Mots-Clés Electronic tagging; Farming cage; Large Atlantic bluefin tuna; Release
Résumé Our knowledge on the biology and ecology of marine species have improved greatly through the use of archival tags by enabling the collection on information from individual in the wild. This is specifically true for large pelagic species such as the Atlantic Bluefin tuna (ABFT, Thunnus thynnus) where, for the first time, it has been possible to confirm through fisheries-independent data, migration patterns, reproductive and feeding behaviours and habitat use. However, large-scale tagging experiments that would enable researchers to tackle group behaviour are difficult to set up. On the one hand, the impact of the actual tagging operation should be as minimal as possible to avoid any change in behaviour of the fish which could influence tag data analyses. On the other hand, large scale tagging experiments require handling a large number of animals in a relatively short period of time. In the present manuscript, a methodology for tagging several large ABFT with satellite tags was tested with ABFT caught from a cage of a Maltese farm. The total time of the operation, from the moment fish were caught by handline to release back to the sea lasted an average of 10 min for the 3 fish tagged. The handling of the fish on the deck lasted less than 2 min. This methodology proved successful at tagging several large (158–182 cm) fishes in a very short time, while ensuring the best conditions for the fish during tagging and subsequent release. This procedure requires substantial logistical preparation and an experienced crew team but, by reducing the time required for the operation, opens up the possibility of large scale tagging activities of large fish held in cages or caught by purse seiners.
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Langue Langue du Résumé Titre Original
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ISSN 0165-7836 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2487
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Auteur (up) Rouyer, T.; Bonhommeau, S.; Giordano, N.; Giordano, F.; Ellul, S.; Ellul, G.; Deguara, S.; Wendling, B.; Bernard, S.; Kerzerho, V.
Titre Tagging Atlantic bluefin tuna from a Mediterranean spawning ground using a purse seiner Type Article scientifique
Année 2020 Publication Revue Abrégée Fish Res.
Volume 226 Numéro Pages 105522
Mots-Clés Eastern Atlantic and Mediterranean stock; Electronic tagging; Large Atlantic bluefin tuna; migration; Migrations; movements; population-structure; Purse seine; thermal biology; thunnus-thynnus
Résumé Atlantic bluefin tuna, Thunnus thynnus, is as an emblematic and commercially valuable large pelagic species. In the past ten years, the purse seine fishery in the Mediterranean represents more than 50 % of the catch. Nowadays, purse seines target large fish and operate during the spawning season in the spawning grounds. Electronic tagging has shed a considerable amount of light on the ecology and behaviour of bluefin tuna over the past twenty years. However, such technique has rarely been applied on large bluefin tunas caught by the Mediterranean purse seine fishery despite its major importance. The logistical constraints related to this specific fishery, combined with the timing of migration of the fish and the requirements related to the handling of big fish have made adequate tagging from purse seines complex. Here we detail such an operation, designed to bridge the knowledge gap on the migratory behaviour of tunas targeted by the purse seine fishery. Three large bluefin tunas from the same school were tagged during the fishing operation of a French purse seine, resulting in a different migration pattern than previous deployments. The fish were tagged onboard in less than 2 min and efficiently, avoiding any subsequent mortality. These results contrast with those from tagging operations carried out in the Northwest Mediterranean, which underlies the importance of tagging operations from purse seines to obtain unbiased description of the movements of the eastern Atlantic bluefin tuna stock in the context of its management.
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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 0165-7836 ISBN Médium
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Notes WOS:000525305200010 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2771
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Auteur (up) Rouyer, T.; Fromentin, J.-M.; Ménard, F.; Cazelles, B.; Briand, K.; Pianet, R.; Planque, B.; Stenseth, N.C.
Titre Complex interplays among population dynamics, environmental forcing, and exploitation in fisheries Type Article scientifique
Année 2008 Publication Revue Abrégée Pnas
Volume 105 Numéro 14 Pages 5420-5425
Mots-Clés Atlantic tuna; North Atlantic Oscillation; time-series analysis
Résumé The patterns of variations in fisheries time series are known to result from a complex combination of species and fisheries dynamics all coupled with environmental forcing (including climate, trophic interactions, etc.). Disentangling the relative effects of these factors has been a major goal of fisheries science for both conceptual and management reasons. By examining the variability of 169 tuna and billfish time series of catch and catch per unit effort (CPUE) throughout the Atlantic as well as their linkage to the North Atlantic Oscillation (NAO), we find that the importance of these factors differed according to the spatial scale. At the scale of the entire Atlantic the patterns of variations are primarily spatially structured, whereas at a more regional scale the patterns of variations were primarily related to the fishing gear. Furthermore, the NAO appeared to also structure the patterns of variations of tuna time series, especially over the North Atlantic. We conclude that the patterns of variations in fisheries time series of tuna and billfish only poorly reflect the underlying dynamics of these fish populations; they appear to be shaped by several successive embedded processes, each interacting with each other. Our results emphasize the necessity for scientific data when investigating the population dynamics of large pelagic fishes, because CPUE fluctuations are not directly attributable to change in species' abundance.
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Volume de collection Numéro de collection Edition
ISSN 0027-8424, 1091-6490 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1669
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Auteur (up) Ruiz, J.; Batty, A.; Chavance, P.; McElderry, H.; Restrepo, V.; Sharples, P.; Santos, J.; Urtizberea, A.
Titre Electronic monitoring trials on in the tropical tuna purse-seine fishery Type Article scientifique
Année 2015 Publication Revue Abrégée ICES J. Mar. Sci.
Volume 72 Numéro 4 Pages 1201-1213
Mots-Clés Bycatch; catch composition; data collection; electronic monitoring system; observers; Purse seining; Tropical tuna
Résumé The difficulty of ensuring adequate statistical coverage of whole fleets is a challenge for the implementation of observer programmes and may reduce the usefulness of the data they obtain for management purposes. This makes it necessary to find cost-effective alternatives. Electronic monitoring (EM) systems are being used in some fisheries as an alternative or a complement to human observers. The objective of this study was to test the use and reliability of EM on the tropical tuna purse-seine fishery. To achieve this objective, seven trips of tuna purse seiners operating in the three Oceans were closely monitored to compare the information provided by EM and on-board observers to determine if EM can reliably document fishing effort, set type, tuna catch, and bycatch. Total tuna catch per set was not significantly different between EM and observer datasets; however, regarding species composition, only main species matched between EM and observers. Success on set-type identification using EM varied between 98.3 and 56.3%, depending on the camera placement. Overall, bycatch species were underestimated by EM, but large bodied species, such as billfishes, were well documented. The analyses in this study showed that EM can be used to determine the fishing effort (number of sets) and total tuna catch as reliably as observers can. Set-type identification also had very promising results, but indicated that refinement of the methods is still needed. To be fully comparable with observer data, improvements for accurately estimating the bycatch will need to be developed in the application and use of the EM system. Operational aspects that need to be improved for an EM programme to be implemented include standardizing installation and on-board catch handling methodology as well as improvements in video technology deployment.
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ISSN 1054-3139, 1095-9289 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1335
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