| Enregistrements |
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 |
2015 |
Publication |
Fisheries Research |
Revue Abrégée |
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| 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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Éditeur |
Murua, H.; Marsac, F.; Eveson, J.P. |
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| ISSN |
0165-7836 |
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pas de |
| Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
1104 |
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| Auteur |
Gilman, E.; Chaloupka, M.; Bach, P.; Fennell, H.; Hall, M.; Musyl, M.; Piovano, S.; Poisson, F.; Song, L. |
| Titre |
Effect of pelagic longline bait type on species selectivity: a global synthesis of evidence |
Type |
Article scientifique |
| Année |
2020 |
Publication |
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Revue Abrégée |
Rev. Fish. Biol. Fish. |
| Volume |
30 |
Numéro |
3 |
Pages |
535-551 |
| Mots-Clés |
atlantic-ocean; Bait; by-catch; Bycatch; caretta-caretta; circle hooks; feeding-behavior; Longline; Mitigation; publication bias; sea-turtles; Selectivity; shark populations; size-selectivity; swordfish xiphias-gladius; Tuna |
| Résumé |
Fisheries can profoundly affect bycatch species with 'slow' life history traits. Managing bait type offers one tool to control species selectivity. Different species and sizes of marine predators have different prey, and hence bait, preferences. This preference is a function of a bait's chemical, visual, acoustic and textural characteristics and size, and for seabirds the effect on hook sink rate is also important. We conducted a global meta-analysis of existing estimates of the relative risk of capture on different pelagic longline baits. We applied a Bayesian random effects meta-analytic regression modelling approach to estimate overall expected bait-specific catch rates. For blue shark and marine turtles, there were 34% (95% HDI: 4-59%) and 60% (95% HDI: 44-76%) significantly lower relative risks of capture on forage fish bait than squid bait, respectively. Overall estimates of bait-specific relative risk were not significantly different for seven other assessed taxa. The lack of a significant overall estimate of relative capture risk for pelagic shark species combined but significant effect for blue sharks suggests there is species-specific variability in bait-specific catch risk within this group. A qualitative literature review suggests that tunas and istiophorid billfishes may have higher catch rates on squid than fish bait, which conflicts with reducing marine turtle and blue shark catch rates. The findings from this synthesis of quantitative and qualitative evidence support identifying economically viable bycatch management measures with acceptable tradeoffs when multispecies conflicts are unavoidable, and highlight research priorities for global pelagic longline fisheries. |
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English |
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Edition |
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| ISSN |
0960-3166 |
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| Notes |
WOS:000555361400001 |
Approuvé |
pas de |
| Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
2843 |
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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 |
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Revue Abrégée |
Aquatic Living Resources |
| Volume |
FirstView |
Numéro |
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Pages |
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| Mots-Clés |
Behaviour; Fish Aggregating Devices; Indian Ocean; Passive acoustic telemetry; skipjack tuna; Yellowfin tuna |
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pas de |
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LL @ pixluser @ |
collection |
193 |
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| Auteur |
Grande, M.; Murua, H.; Zudaire, I.; Arsenault-Pernet, E.J.; Pernet, F.; Bodin, N. |
| Titre |
Energy allocation strategy of skipjack tuna Katsuwonus pelamis during their reproductive cycle |
Type |
Article scientifique |
| Année |
2016 |
Publication |
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Revue Abrégée |
J. Fish Biol. |
| Volume |
89 |
Numéro |
5 |
Pages |
2434-2448 |
| Mots-Clés |
bonito euthynnus-pelamis; cod gadus-morhua; fatty-acid-composition; highly migratory fish; Income breeder; Indian Ocean; lipid classes; oocyte growth; reproduction; sarda-sarda; teleost fish; thunnus-albacares; Tropical tuna; western indian-ocean |
| Résumé |
The lipid composition of somatic and reproductive tissues was determined for female skipjack tuna Katsuwonus pelamis caught in the western Indian Ocean between latitude 10 degrees N and 20 degrees S and longitude 40 degrees and 70 degrees E. The highest total lipid (TL) contents were in the liver and gonads, with white muscle levels approximately three-fold lower. Three lipid classes dominated: triacylglycerols (TAG), sterol esters and wax esters (SE-WE) and phospholipids (PL). Collectively, these accounted for between 70 and 80% of TLs. Changes in lipid concentrations were evaluated over the maturation cycle. Immature fish had the lowest gonad and liver TL levels; concentrations of TL, TAG, SE-WE and PL accumulated from immature to mature (spawning-capable) phase, reflecting sustained vitellogenic activity of the liver and a transfer of lipids to developing oocytes from the onset of vitellogenesis. Gonado-somatic and hepato-somatic indices were positively correlated with each other and positively related to TL in the gonads and liver. Fulton's condition index and lipid concentrations in muscle did not vary significantly over the maturation cycle; fat content in the main storage tissues was undepleted as the ovary developed. Hence, K. pelamis apparently supports reproduction directly from food intake over the breeding season. In the gonads, reserve lipids (SE-WE and TAG) and sterols were related to batch fecundity but this was not the case for somatic and hepatic tissues. These results suggest that K. pelamis utilizes an income breeding strategy. |
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English |
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0022-1112 |
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pas de |
| Numéro d'Appel |
MARBEC @ alain.herve @ |
collection |
1685 |
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| Auteur |
Guillotreau, P.; Salladarre, F.; Dewals, P.; Dagorn, L. |
| Titre |
Fishing tuna around Fish Aggregating Devices (FADs) vs free swimming schools : skipper decision and other determining factors |
Type |
Article scientifique |
| Année |
2011 |
Publication |
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Revue Abrégée |
Fisheries Research |
| Volume |
109 |
Numéro |
2-3 |
Pages |
234-242 |
| Mots-Clés |
Fish Aggregating Devices; Purse-seine; Skipper effect; tuna |
| Résumé |
Fish Aggregating Devices (FADs) are increasingly used by tuna purse-seine fleets all around the world, modifying the species catch composition. We analyse the determinants of FAD vs free school (FS) fishing, including the skipper effect, and environmental and economic factors. A multivariate and econometric analysis of a panel dataset for the French purse-seine fleet in the Indian Ocean (1980-2007), complemented by a survey of fishers, demonstrates the influential role of climate and prey on FAD fishing and also emphasises individual skipper preference. However, we found that the major determinant of FAD fishing remains the growing fishing capacity (use of bigger vessels, satellite buoys, echo-sounders, supply vessels), thus modifying the species catch composition towards smaller tuna. Other things being equal, raising the proportion of FAD sets by 1% would increase the catches of skipjack by 1.3% and decrease those of large yellowfin tuna by 1.7%. This result shows that the control of effort and investment could be adapted through management measures to encourage one fishing method. |
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Numéro de collection |
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Edition |
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| ISSN |
0165-7836 |
ISBN |
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Médium |
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Expédition |
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Conférence |
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| Notes |
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Approuvé |
pas de |
| Numéro d'Appel |
LL @ pixluser @ |
collection |
143 |
| Lien permanent pour cet enregistrement |
