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Auteur Walker, E.; Rivoirard, J.; Gaspar, P.; Bez, N.
Titre From forager tracks to prey distributions: an application to tuna vessel monitoring systems (VMS) Type Article scientifique
Année 2015 Publication Ecological Applications Revue Abrégée
Volume 25 Numéro 3 Pages 826-833
Mots-Clés Gps; multivariate geostatistics; presence index; spatiotemporal distribution; trajectometry; Tropical tuna; vessel monitoring system (VMS)
Résumé In the open ocean, movements of migratory fish populations are typically surveyed using tagging methods that are subject to low sample sizes for archive tags, except for a few notable examples, and poor temporal resolution for conventional tags. Alternatively, one can infer patterns of movement of migratory fish by tracking movements of their predators, i.e., fishing vessels, whose navigational systems (e.g., GPS) provide accurate and frequent VMS (vessel monitoring system) records of movement in pursuit of prey. In this paper, we develop a state-space model that infers the foraging activities of fishing vessels from their tracks. Second, we link foraging activities to probabilities of tuna presence. Finally, using multivariate geostatistical interpolation (cokriging) we map the probability of tuna presence together with their estimation variances and produce a time series of indices of abundance. While the segmentation of the trajectories is validated by observers' data, the present VMS-index is compared to catch rate and proved to be useful for management perspectives. The approach reported in this manuscript extends beyond the case study considered. It can be applied to any foragers that engage in an attempt of capture when they see prey and for whom this attempt is linked to a tractable change in behavior.
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ISSN (up) 1051-0761 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1116
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Auteur Escalle, L.; Gaertner, D.; Chavance, P.; Delgado de Molina, A.; Ariz, J.; Mérigot, B.
Titre Forecasted consequences of simulated FAD moratoria in the Atlantic and Indian Oceans on catches and bycatches Type Article scientifique
Année 2017 Publication Revue Abrégée ICES J. Mar. Sci.
Volume 74 Numéro 3 Pages 780-792
Mots-Clés area; Bycatch; ecosystem approach to fisheries; fish aggregation device; management; Megafauna; Monte Carlo simulations; Purse-seine fishery; time; time-area restriction; tropical tuna purse-seine fishery; Tuna
Résumé Given the increasingly extensive use of drifting fish aggregation devices (FADs) by the purse-seine fisheries targeting tropical tunas, fishing effort restrictions have been introduced to manage tropical tuna stocks. However, these measures are focused on the protection of juvenile tunas and do not take account of the potential impact on bycatch or associated megafauna (whales and whale sharks). An iterative “fishing-day” Monte Carlo simulation model was developed to investigate the consequences on tropical tunas and bycatch of introducing extensive area 6-month moratoria on FAD activities. The model allowed for variability in a range of plausible values of the parameters characterizing the fishing operations conducted by European purse-seiners in the eastern tropical Atlantic and western Indian Oceans for the period 2005-2014. Monte Carlo simulations, using probabilities based on these fishery data, were carried out for the French and Spanish fishing fleets separately to account for differences in fishing strategies. The models predicted a decrease in FAD sets and an increase in free school sets. As a consequence, the catch of small tuna (<10 kg) decreased while the catch of large tuna (>= 10 kg) increased, leading to an overall increase in tuna catch of 100-200 tons/year/vessel in the Atlantic Ocean, and a decrease of 400-1500 tons/year/vessel in the Indian Ocean. The bycatch decreased in the Indian Ocean, while in the Atlantic Ocean billfishes, turtles and chondrichthyans bycatch increased slightly and other bony fishes decreased. Because fishing practices were modified, whale and whale shark associated sets increased slightly in the Indian Ocean.
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Langue English Langue du Résumé Titre Original
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ISSN (up) 1054-3139 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 2105
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Auteur Kaplan, D.; Chassot, E.; Amande, J.M.; Dueri, S.; Demarcq, H.; Dagorn, L.; Fonteneau, A.
Titre Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives Type Article scientifique
Année 2014 Publication Revue Abrégée Ices Journal of Marine Science
Volume 71 Numéro 7 Pages 1728-1749
Mots-Clés Bycatch; conservation; Indian Ocean; Marine protected areas (MPAs); pelagic; spatial management of fisheries; tropical tuna fisheries
Résumé Effective use of spatial management in the pelagic realm presents special challenges due to high fish and fisher mobility, limited knowledge and significant governance challenges. The tropical Indian Ocean provides an ideal case study for testing our ability to apply existing data sources to assessing impacts of spatial management on tuna fisheries because of several recent controversial spatial closures. We review the scientific underpinnings of pelagic MPA effects, spatio-temporal patterns of Indian Ocean tuna catch, by catch and fish movements, and the consequences of these for the efficacy of spatial management for Indian Ocean tropical tuna fisheries. The tropical Indian Ocean is characterized by strong environmental fluctuations, regular seasonal variability in catch, large observed tuna displacement distances, relatively uniform catch-per-unit-effort and bycatch rates over space, and high fisher mobility, all of which suggest significant variability and movement in tropical tuna fisheries that are simply not well adapted to static spatial closures. One possible exception to this overall conclusion would be a large time/area closure east of Somalia. If closed for a significant fraction of the year it could reduce purse-seine bycatch and juvenile tuna catch. Dynamic closures following fish migratory patterns are possible, but more focused information on fish movements will be needed for effective implementation. Fortunately, several recent improvements in conventional fishery management and reporting will likely enhance our ability to evaluate spatial and non-spatial management options in the near future, particularly as pertaining to bycatch species.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1199
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Auteur 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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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1335
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Auteur Díez, G.; Moreno, G.; Galaz, T.; Dagorn, L.; Murua, J.
Titre Digestive activity and stomach temperature in farmed bluefin tuna Thunnus thynnus measured by acoustic tag Type Article scientifique
Année 2017 Publication Revue Abrégée J Fish Biol
Volume 90 Numéro 6 Pages 2504-2511
Mots-Clés acoustic; Bluefin tuna; digestion; farm; tag; Temperature
Résumé Eight farmed Atlantic bluefin tuna Thunnus thynnus were tagged with temperature and depth transmitters inserted in chub mackerels Scomber colias to characterize their digestive activity, feeding physiology and behaviour in captivity. Results obtained in the experiment can be used to optimize daily T. thynnus feeding strategy in farms, reducing the early regurgitation of food and thus the environmental effects of inappropriate feeding practices.
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ISSN (up) 1095-8649 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2145
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