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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 (down) 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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Auteur Gaertner, D.; Hallier, J.-P.
Titre Tag shedding by tropical tunas in the Indian Ocean and other factors affecting the shedding rate Type Article scientifique
Année (down) 2015 Publication Fisheries Research Revue Abrégée
Volume 163 Numéro Si Pages 98-105
Mots-Clés averaging; Bayesian model; Beta-binomial model; Indian Ocean; Shedding rate; Tagging data; Tropical tunas
Résumé A key objective of the Regional Tuna Tagging Project Indian Ocean was to estimate tag-shedding rates, Type-I (immediate tag shedding) and Type-II (long-term tag shedding). To assess this, a series of double-tagging experiments (26,899 double tags released with 4555 recoveries) were conducted as part of the broader tagging program. After omitting data from tags placed by less experienced taggers, the results of our analyses did not show any evidence that individual differences between taggers (i.e., a tagger effect) impacted estimates of tag-shedding rates. However, it was shown that the probability of retaining the second tag (inserted in the left side of the fish) was larger than retaining the first tag (inserted in the right side, i.e., the side typically tagged in single-tagging experiments). We used a Bayesian model averaging approach to account for model uncertainty in the estimates of the parameters a and L used to calculate the probability of tag retention Q(t)= alpha e-((L t)) for the right tag. The parameter estimates were alpha = 0.993 and L (per year) = 0.030 (skipjack); alpha = 0.972 and L (per year) = 0.040 (yellowfin); and alpha = 0.990 and L (per year) = 0.021 (bigeye). These results agree with estimates obtained by other large-scale tropical tuna tagging projects. We showed that tag loss has a moderate impact on the underestimation of the exploitation rate (bias = 2-6% depending on the tuna species). However, non-reporting leads to a bias of around 7% when using the high reporting rate estimate of purse seiners. Finally, tag shedding (specifically Type-II shedding) modified the individual weights of the samples of recaptures. Consequently, the total instantaneous mortality estimates (Z; calculated from mean times-at-large) were reduced by a range of 1-3%.
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Editeur Lieu de Publication Éditeur Murua, H.; Marsac, F.; Eveson, J.P.
Langue 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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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1104
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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 (down) 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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Volume de collection Numéro de collection Edition
ISSN 1051-0761 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1116
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Auteur Mazurais, D.; Covès, D.; Papandroulakis, N.; Ortega, A.; Desbruyeres, E.; Huelvan, C.; Le Gall, M.M.; de la Gándara, F.; Cahu, C.L.
Titre Gene expression pattern of digestive and antioxidant enzymes during the larval development of reared Atlantic bluefin tuna (ABFT), Thunnus thynnus L Type Article scientifique
Année (down) 2015 Publication Revue Abrégée Aquac Res
Volume 46 Numéro 10 Pages 2323-2331
Mots-Clés antioxidant; development; digestion; expression; gene; Tuna
Résumé The aim of this study was to determine whether mortality observed during the larval development of reared bluefin tuna (Thunnus thynnus) could be related to improper expression profiles of key genes involved in digestive or antioxidant response capabilities. Tuna larvae were sampled at hatching, 2, 5, 10, 15 and 20 dph (days post hatching) for the relative quantification of transcripts encoded by genes involved in digestive [trypsinogen 1 (TRYP1), alpha-amylase (AMY), aminopeptidase N (ANPEP)] and antioxidant [catalase (CAT)] functions. The levels of expression of ANPEP related to the development and maturation of intestinal function increased from 5 to 20 dph. Furthermore, AMY and TRYP1 genes, which are pancreatic enzymes implicated in carbohydrate and peptide digestions exhibit a typical peak of expression at 5 and 15 dph respectively. The antioxidant enzyme, CAT, exhibited higher mRNA levels during the first stage of larval development. In conclusion, our investigation indicates that the expression of genes involved in digestive and antioxidant physiological processes followed typical patterns which could not explain high mortality rate observed during the first stage of larval development.
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Volume de collection Numéro de collection Edition
ISSN 1365-2109 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1455
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Auteur Arrizabalaga, H.; Dufour, F.; Kell, L.; Merino, G.; Ibaibarriaga, L.; Chust, G.; Irigoien, X.; Santiago, J.; Murua, H.; Fraile, I.; Chifflet, M.; Goikoetxea, N.; Sagarminaga, Y.; Aumont, O.; Bopp, L.; Herrera, M.; FROMENTIN, J.-M.; Bonhomeau, S.
Titre Global habitat preferences of commercially valuable tuna Type Article scientifique
Année (down) 2015 Publication Deep Sea Research Part II: Topical Studies in Oceanography Revue Abrégée
Volume 113 Numéro Pages 102-112
Mots-Clés Habitat; Tuna fisheries; Catch/ effort; Environmental conditions; Quotient analysis; Generalized Additive Models; Ecosystem Approach to Fisheries Management
Résumé In spite of its pivotal role in future implementations of the Ecosystem Approach to Fisheries Management, current knowledge about tuna habitat preferences remains fragmented and heterogeneous, because it relies mainly on regional or local studies that have used a variety of approaches making them difficult to combine. Therefore in this study we analyse data from six tuna species in the Pacific, Atlantic and Indian Oceans in order to provide a global, comparative perspective of habitat preferences. These data are longline catch per unit effort from 1958 to2007 for albacore, Atlantic bluefin, southern bluefin, bigeye, yellowfin and skipjack tunas. Both quotient analysis and Generalized Additive Models were used to determine habitat preference with respect to eight biotic and abiotic variables. Results confirmed that, compared to temperate tunas, tropical tunas prefer warm, anoxic, stratified waters. Atlantic and southern bluefin tuna prefer higher concentrations of chlorophyll than the rest. The two species also tolerate most extreme sea surface height anomalies and highest mixed layer depths. In general, Atlantic bluefin tuna tolerates the widest range of environmental conditions. An assessment of the most important variables determining fish habitat is also provided.
Adresse Ifremer, UMR 212 EME, boulevard Jean Monnet, BP 171, Sete Cedex, 34203, France
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Editeur Elsevier BV Lieu de Publication Éditeur
Langue Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0967-0645 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ 31190 collection 981
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