Search

An objective of the Atlantic Ocean Tropical tuna Tagging Programme (AOTTP) was to estimate Type-I (immediate) and Type-II (long-term) tag-shedding rates for tropical Atlantic tunas from double-tagging experiments. Historical information on tuna tag-shedding studies conducted in different parts of the world was incorporated as prior distributions using a Bayesian approach to estimate the new tag-shedding parameters. Type-I and Type-II tag-shedding rates were respectively estimated at 0.007 and 0.084/yr for bigeye tuna, 0.021 and 0.051/yr for skipjack and 0.021 and 0.088/yr for yellowfin tuna. Using realizations derived from the MCMC posterior distributions, the shedding rate was estimated to reach 50% of the tags after seven and a half years at sea for yellowfin and after eight years at sea for bigeye tuna. The loss rate of conventional tags is lower for skipjack. Our results suggested that continuous Type-II shedding rate is size-dependant for yellowfin and bigeye (i.e., showing a three-fold increase between individuals less than 45 cm fork length (FL) at release and fishes larger than 65 cm FL). This study reinforces the need to account for tag-shedding along with other sources of uncertainty, such as reporting rate, in order to accurately estimate the exploitation and mortality rates derived from tagging data.

[EN] Abundance index for Eastern Atlantic skipjack was derived from the European purse seiner CPUEs series (2010-2019) for fishing operations made on drifting FADs non-owned by the vessel. By selecting non-owned dFADs only, i.e., dFADs for which the purse seiner has no previous information for detecting the object and on the corresponding aggregated biomass, we relaxed as possible the assumptions on the non-random detection process as well as on the effort creep over the years. The VAST methodology was used to standardized the SKJ CPUE. A GLMM approach has been also applied to compare the outputs when using an alternative modelling approach., [FR] L'indice d'abondance du listao de l'Atlantique Est a été dérivé de la série de CPUE des senneurs de l'UE (2010-2019) pour les opérations de pêche effectuées sous des DCP dérivants (DCPd) n'appartenant pas au navire. En ne sélectionnant que des DCPd n'appartenant pas au navire, c'est-à-dire des DCPd pour lesquels le senneur ne dispose pas d'informations antérieures sur la détection de l'objet et sur la biomasse agrégée correspondante, nous avons assoupli autant que possible les postulats sur le processus de détection non aléatoire ainsi que sur l'évolution de l'effort au fil des ans. La méthodologie VAST a été utilisée pour standardiser les CPUE du listao. Une approche GLMM a également été appliquée pour comparer les résultats lors de l'utilisation d'une approche de modélisation alternative., [ES] El índice de abundancia del listado del Atlántico oriental se ha obtenido a partir de la serie de CPUE de los cerqueros europeos (2010-2019) para las operaciones de pesca realizadas sobre DCP a la deriva que no son propiedad del buque. Al seleccionar únicamente los DCP que no son propiedad del buque, es decir, los DCPd para los que el cerquero no dispone de información previa para la detección del objeto y sobre la biomasa agregada correspondiente, se relajaron al máximo los supuestos sobre el proceso de detección no aleatorio, así como sobre el incremento del esfuerzo a lo largo de los años. Se utilizó la metodología VAST para estandarizar la CPUE de listado. También se ha aplicado un enfoque GLMM para comparar los resultados cuando se utiliza un enfoque de modelación alternativo.

The time series of EU purse seine fleet catches per unit effort (CPUE) of yellowfin tuna (YFT) from the Atlantic Ocean were standardized using an extension of the Delta-lognormal GLMM to three components. The aim was to depict the trend in abundance for adult YFT observed in free schools (FSC). The originality of this work relied on the inclusion of i) null sets, considered as presence of YFT FSC, ii) fishing days without set, considered as absence of FSC, iii) EU fishing agreement in the exclusive economic zones driving EU purse seine fleet presence in these areas, and iv) time spent by centroid cell by boat by day to constrain detectability. Standardized CPUE for FSC was thus defined as the product of the number of set (positive and null) by spatio-temporal strata, the proportion of sets with large YFT (>10 kg) and the catch per large YFT set. To detect strata without sets, all activities recorded in captain logbooks were used for the period 1993-2018. This new standardization approach, therefore, represents a significant advance over previous efforts, though there are a number of avenues for future progress.

Turtles (Testudines) form a monophyletic group with a highly distinctive body plan. The taxonomy and phylogeny of turtles are still under discussion, at least for some clades. Whereas in most previous studies, only a few species or genera were considered, we here use an extensive compilation of DNA sequences from nuclear and mitochondrial genes for more than two thirds of the total number of turtle species to infer a large phylogeny for this taxon. Our results enable us to discuss previous hypotheses on species phylogeny or taxonomy. We are thus able to discriminate between competing hypotheses and to suggest taxonomical modifications. Finally, we pinpoint the remaining ambiguities for this phylogeny and the species for which new sequences should be obtained to improve phylogenetic resolution.

Turtles (Testudines) form a monophyletic group with a highly distinctive body plan. The taxonomy and phylogeny of turtles are still under discussion, at least for some clades. Whereas in most previous studies, only a few species or genera were considered, we here use an extensive compilation of DNA sequences from nuclear and mitochondrial genes for more than two thirds of the total number of turtle species to infer a large phylogeny for this taxon. Our results enable us to discuss previous hypotheses on species phylogeny or taxonomy. We are thus able to discriminate between competing hypotheses and to suggest taxonomical modifications. Finally, we pinpoint the remaining ambiguities for this phylogeny and the species for which new sequences should be obtained to improve phylogenetic resolution.