-Bycatch of several groups of species and their characteristics are presented for the period 2003 to 2007 for the European purse seine tuna fishery operating in the Atlantic Ocean. Data were collected through French and Spanish observer programmes and represented a total of 27 trips corresponding to 2.9% coverage. Bycatch is defined as nontargeted species and small or damaged target species. Bycatch species composition, main species length, sex ratio and the fate of the most common species are presented first. Stratified ratios relative to landings of major commercial tunas were then used to estimate the total bycatch; these ratios were considered the most appropriate variable for extrapolation. Stratification was based on the fishing mode (free school vs. floating object), season (quarters) and spatial areas. The annual average bycatch was estimated at about 6400 t, corresponding to a mean annual value of 80.8 t per 1000 t of tuna landed or 7.5% of the total catch. Tunas represent 83% (67.2 t/1000 t) of the total bycatch, followed by other bony fishes (10%, 7.8 t/1000 t), billfishes (5%, 4.0 t/1000 t), sharks (1%, 0.9 t/1000 t) and rays (1%, 0.9 t/1000 t). Based on estimates of the annual bycatch, 16% was kept on board and sold in local markets.Key words: Bycatch / Discards / Tuna fisheries / Purse seining / Atlantic Ocean Résumé -Les quantités de captures accessoires de plusieurs groupes d'espèces ainsi que leurs caractéristiques sont présentées pour la pêcherie thonière européenne à la seine opérant dans l'océan Atlantique pour la période [2003][2004][2005][2006][2007]. Les données ont été collectées lors de programmes d'observateurs embarqués français et espagnols représentant un total de 27 marées soit un taux de couverture de 2,9 % des marées totales. Les captures accessoires sont définies ici comme les espèces non ciblées ainsi que les individus petits ou abîmés des espèces-cibles. La composition spécifique des captures accessoires, la structure de taille des principales espèces, le sex-ratio et le devenir des espèces les plus communes sont présentés. La méthode des ratios par rapport aux débarquements d'espèces commerciales est ensuite utilisée pour estimer la quantité totale de capture accessoire. Ces ratios ont été considérés comme la variable la plus appropriée pour l'extrapolation. Une stratification a été utilisée, basée sur le mode de pêche (pêche sur banc libre versus pêche sur objet flottant), le trimestre et les zones spatiales. La quantité de capture accessoire annuelle moyenne est estimée à 6400 t, correspondant à une valeur annuelle moyenne de 80,8 t par 1000 t de thons commercialisés ou 7,5 % de la capture totale. Les thons représentent 83 % (67,2 t/1000 t) du total des captures accessoires suivis par les autres poissons osseux (10 % ; 7,8 t/1000 t), les poissons porte-épées (5 % ; 4,0 t/1000 t), les requins (1 % ; 0,9 t/1000 t) et les raies (1 % ; 0,9 t/1000 t). On estime que 16 % de ces captures accessoires est conservé à bord et vendu sur le marché local.

-Ecological risk assessment is a useful methodology for assisting the management of fisheries from an ecosystem perspective. Atlantic tuna fisheries, managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), are economically important and interact with several bycatch species. In spite of these interactions, no comprehensive ecological risk assessment has been conducted for bycatch species caught in ICCAT fisheries. In this paper, we followed a two stage approach with the objective of assessing the relative risk of species being negatively impacted by Atlantic tuna fisheries. An analysis of the ICCAT bycatch species list (which includes all species reported to have interacted with different tuna fishing gears operating in the Atlantic) revealed that most of these species are caught in longline fisheries, followed by gillnets and purse seines. According to the IUCN red list, 7 species of the ICCAT bycatch list (3 coastal sharks, 3 sea turtles and one seabird) are categorized as critically endangered. In our study, and based on their life history characteristics, marine mammals and coastal sharks caught in ICCAT fisheries showed the highest intrinsic vulnerability values. A productivity susceptibility analysis for the European Union (EU) tropical tuna purse seine fleet and the United States (US) pelagic longline fleet revealed two groups with high relative risk scores. The first one included pelagic and coastal sharks, characterized by relatively low productivities, and the second one included teleosts, characterized by higher productivities but high susceptibility to purse seine and longline gears. Some alternative approaches to conduct productivity susceptibility analyses in the context of ecological risk assessments are discussed.

-Time-area closures have become a frequently used tool to control fishing effort and protect feeding and spawning areas. However, because time-area closure strata are mainly based on biological and ecological considerations, and do not accounts for fishermen's behavior-at-sea, this type of regulation tool may not entirely achieve its objectives. With the aim of comparing the impact of two different time-area regulations: (1) a moratorium on Fish Aggregating Devices (FAD) sets (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) and (2) a no-take area for surface fleets (2005)(2006)(2007)(2008)(2009)(2010) on the dynamics of the European (EU) tuna purse seine fleet operating in the eastern tropical Atlantic, several fishery indicators were evaluated through a Before-After, Control-Impact (BACI) approach. The results showed that prior to any regulation, the fleet used to be concentrated within the Gulf of Guinea area. During the first years of the moratorium on FAD (from November to January within a large region in the eastern Atlantic) there was a movement towards outside the protected area, increasing the total sets on FAD (restricted fishing activity). In general, this moratorium fulfilled its objectives; however, it was not respected during the last years of this regulation. The no-take time-area closure restricted all tuna catches for the surface fisheries but only in November and within a small area (i.e., the Picolo zone). As a result, there was an increase in activities on free schools outside the no-take area. Our findings suggest the use of some simple fishery indicators to understand fleet dynamics as a complement of ecological information before implementing new time area closures. Furthermore, since tunas are highly mobile species, anticipating the possible re-allocation of effort of purse seiners to adjacent areas in response to the spatial regulation is required to design different candidate time-area closures and to evaluate their effectiveness to protect juvenile tunas.

Within the Ecosystem-based fisheries management framework, we evaluated the changes over time in bycatch species of the European tuna purse-seine fishery operating in the eastern Atlantic Ocean. Bycatch data was collected during two scientific observer programs conducted in the late 1990s and in the late 2000s. Over these two time periods, we compared the temporal trends in bycatch species composition, the probability of occurrence of functional groups per fishing set, the spatio-temporal species richness and the potential impact on several species listed in the red list of the International Union for Conservation of Nature (IUCN). The analyses were performed separately on the two main fishing modes of the fleet, i.e. sets on free-swimming school sets and on fish aggregating devices (FADs). Owing data quality constraints, we did not estimate bycatch rates. Ours results showed that the species composition of sharks caught on FADs decreased over time. The total species richness was higher for FAD sets than for free-swimming school sets (87 vs. 61 species respectively), such difference is common between fishing modes worldwide.

Tuna fisheries have been identified as one of the major threats to populations of other marine vertebrates, including sea turtles, sharks, seabirds and marine mammals. The development of technical mitigation measures (MM) in fisheries is part of the code of conduct for responsible fisheries. An in-depth analysis of the available literature regarding bycatch mitigation in tuna fisheries with special reference to elasmobranchs was undertaken. Studies highlighting promising MMs were reviewed for four tuna fisheries (longline, purse seine, driftnets and gillnet, and rod and line – including recreational fisheries). The advantages and disadvantages of different MMs are discussed and assessed based on current scientific knowledge. Current management measures for sharks and rays in tuna Regional Fishery Management Organizations (t-RFMOs) are presented. A review of relevant studies examining at-vessel and postrelease mortality of elasmobranch bycatch is provided. This review aims to help fisheries managers identify pragmatic solutions to reduce mortality on pelagic elasmobranchs (and other higher vertebrates) whilst minimizing impacts on catches of target tuna species. Recent research efforts have identified several effective MMs that, if endorsed by t-RFMOs, could reduce elasmobranchs mortality rate in international tropical purse seine tuna fisheries. In the case of longline fisheries, the number of operational effective MMs is very limited. Fisheries deploying driftnets in pelagic ecosystems are suspected to have a high elasmobranchs bycatch and their discard survival is uncertain, but no effective MMs have been field validated for these fisheries. The precautionary bans of such gear by the EU and by some t-RFMOs seem therefore appropriate. Recreational tuna fisheries should be accompanied by science-based support to reduce potential negative impacts on shark populations. Priorities for research and management are identified and discussed.

-In order to assess the latitudinal variability in growth of the eastern Atlantic skipjack (Katsuwonus pelamis), conventional tagging data collected by the International Commission of the Conservation of Atlantic Tunas (ICCAT) since the 1960s are reanalyzed using a modified version of the von Bertalanffy-Fabens growth model. An analysis of the latitudinal patterns of recaptures showed that the lowest mixing rate between northern and southern regions was evidenced at 10• N Latitude. Since it is theoretically admitted that growth parameters L ∞ and K are negatively correlated, we substituted L ∞ into the growth equation model by a simple bioenergetic function of K fitted from existing studies on skipjack growth parameters. The likelihood for the meta-analysis of growth is combined with the likelihoods from the two regional tagging data with the aim of estimating simultaneously K in both areas and to transfer adequately uncertainties associated with the different data sets. From this study, it was showed that fish inhabiting waters south of 10• N latitude can be expected to grow generally larger but at slower rate than in the North (L ∞ = 112.34 cm vs. 89.38 cm, and K = 0.14 vs. 0.38, respectively). Our results are consistent with the range of growth estimates obtained in the Atlantic Ocean and in different parts of the World's oceans. In contrast, the estimates of L ∞ and K done in the Senegalese region in the 1980s within the framework of the Skipjack Year Program, and traditionally applied by IC-CAT, are not supported by the present study. The findings concerning the phenotypic plasticity exhibited by growth of skipjack among latitudinal regions suggest potential differences in fish population productivity and consequently imply that non-conventional stock assessment methods such as catch-at size/growth transition matrix per region could be used to assess the responses of skipjack to exploitation.Key words: Skipjack tuna / Growth rate / Conventional tagging / Combined likelihood / Bioenergetic function Résumé -Variabilité de la croissance du listao (Katsuwonus pelamis) entre les secteurs de l'Atlantique Est : utilisation de données de marquage-recapture dans un contexte de méta-analyse. Dans le but d'évaluer la variabilité latitudinale de la croissance du listao (Katsuwonus pelamis) dans l'Atlantique Est, les données de marquage traditionnel collectées par l'ICCAT depuis le début des années soixante ont été reanalysées à l'aide d'une version modifiée du modèle de croissance de von Bertalanffy-Fabens. L'analyse des taux de recaptures par strates longitudinales montre que les échanges sont minima entre le Nord et le Sud au niveau de la latitude 10• N. Etant donné qu'il est admis que les estimations des paramètres de la courbe de croissance L ∞ et K sont corrélées, nous proposons de substituer, dans l'équa-tion de croissance, L ∞ par une simple fonction bioénergétique de K ajustée à partir des paramètres de croissance obtenus dans la littérature sur le sujet. La fonction de vraisemblance pour ces données d...

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