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Gaertner Daniel, Hallier Jean-Pierre. (2015). Tag shedding by tropical tunas in the Indian Ocean and other factors affecting the shedding rate. In : Murua H. (ed.), Marsac Francis (ed.), Eveson J.P. (ed.) IO Tuna tagging. Fisheries Research, 163 (SI), 98-105. ISSN 0165-7836

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Lien direct chez l'éditeur doi:10.1016/j.fishres.2014.02.025

Titre
Tag shedding by tropical tunas in the Indian Ocean and other factors affecting the shedding rate
Année de publication2015
Type de documentArticle référencé dans le Web of Science WOS:000348971300009
AuteursGaertner Daniel, Hallier Jean-Pierre.
InMurua H. (ed.), Marsac Francis (ed.), Eveson J.P. (ed.) IO Tuna tagging
SourceFisheries Research, 2015, 163 (SI), p. 98-105. ISSN 0165-7836
RésuméA 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%.
Plan de classementRessources halieutiques [040]
Descr. géo.OCEAN INDIEN
LocalisationFonds IRD [F B010063907]
Identifiant IRDfdi:010063907
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010063907

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