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International audience; The Grand Récif of Toliara (GRT) in Madagascar is a large (33 km2) barrier reef system of the SW Indian Ocean that had been well investigated in the 1960s and early 1970s. A massive degradation of the reef has been reported since at least the early 1980s, just a few years after research activities ceased in the area. Examination of historical aerial photographs and modern high-resolution remote sensing images confirms a continuous loss of coral habitat on GRT outer reef flats between 1962 and 2011, with an average loss of 65 % and a range of 37-79 % loss during this 50-year period. The usual suspects of coral community declines (cyclones, bleaching and sedimentation) may have contributed to the demise of the GRT. However, an independent study (Salimo 1997) suggests that the chronic pressure of fisherman gleaning on reef flats with destructive tools is the main driver of the observed changes. Salimo's reported level of frequentation (6.8 fishermen per day and per km−2) and rates of destruction per fisherman (7.7 m2 of coral habitat h−1) yield a cumulated overall loss in agreement with the image-based rates of habitat loss. The GRT is unlikely to recover because this chronic stress is unlikely to decrease in the near future. Indeed, the GRT daily provides subsistence fishery resources for local Vezo people and to agriculturalist or pastoralist ethnic groups who have turned to exploiting coastal resources due to increasing aridity and dwindling agricultural and livestock production

Little is known about the effects of mud crabs population patterns on their exploitation. We used complementary approaches (experimental, fisher-based) to investigate how small-scale variations in density, size and sex-ratio related to the ecology of S. serrata may impact fishing practices in New Caledonia. Crabs were measured/sexed across 9 stations in contrasted mangrove systems between 2007 and 2009. Stations were described and classified in different kinds of mangrove forests (coastal, riverine, and estuarine); vegetation cover was qualitatively described at station scale. Annual catch was used as an indicator of fishing pressure. Middle-scale environmental factors (oceanic influence, vegetation cover) had significant contributions to crab density (GLM, 84.8% of variance), crab size and sex-ratio (

This study provides a historical overview of the use of drifting fish aggregating devices (DFADs) in purse seine fisheries since the early 1990s, using global tuna fisheries datasets from the four tuna Regional Fisheries Management Organizations (RFMOs). Tropical tuna purse seine fisheries typically target large yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tunas on free-swimming schools and skipjack (Katsuwonus pelamis )a nd juveniles of yellowfin and bigeye associated with drifting objects. DFADs have enabled global skipjack catches to markedly increase, and have also introduced major scientific issues for all tuna-RFMOs. In particular, they have strongly modified the fishing strategies of purse seiners that fish on a combination of free-swimming and DFAD-associated schools. Consequently, the cumulated search time traditionally used to quantify nominal fishing effort to assess the status of tuna stocks is inconsistent and cannot be used to derive time series of abundance indices from catch-per-unit of-effort (CPUE). In addition, the lack of information available on the construction, deployment, and use of DFADs has prevented effective monitoring of the fishing pressure over the last two decades exerted by purse seine fleets using this fishing mode. Juveniles of tropical tunas represent a substantial proportion of purse seine catch on DFADs in the three oceans, which has raised particular concern for some bigeye stocks that have been subject to overfishing in the past. Catches of juvenile tunas by DFAD fishing may also result in a decrease in recruitment for fisheries that target adult tunas such as longliners. In addition, some demographic parameters of tunas and other species associated with DFADs may be affected by the resultant habitat modification arising from the widespread deployment of DFADs. Evidence in the literature and provided by the ratio-estimator method suggest that fishing DFAD-associated schools may result in about 100 000 t of bycatch and discards annually. In addition, there is further potential for ghost fishing related mortality of sensitive species such as marine turtles and pelagic sharks. In this context and following a precautionary approach, we finally discuss the increasing need for all tuna-RFMOs to reduce, or at least monitor and control, the use of DFADs to mitigate their adverse effects not only on yellowfin and bigeye stocks but also on open-ocean ecosystems.

Trabajo final presentado por Xavier Corrales Ribas para el Master en Gestión Pesquera Sostenible de la Universitat d'Alacant (UA), realizado bajo la dirección de la Dra. Marta Coll Monton y de la Dra. Isabel Palomera Laforga del Institut de Ciències del Mar (ICM-CSIC).-- 168 pages, [ES] Se ha desarrollado un modelo de equilibrio de masas para caracterizar la estructura y funcionamiento de la plataforma y talud continental del Mediterráneo noroccidental, desde Toulon hasta el Cabo de la Nao (modelo del NWMS). El modelo se ha construido a partir de aplicaciones anteriores de Ecopath with Ecosim en áreas del Mediterráneo noroccidental (golfo de León y sur del mar Catalán) El modelo representa el ecosistema en el inicio del 2000, cubre 45.547 km2 e incluye las batimetrías de 0 a 1000 m de profundidad. El área de estudio ha sido determinada específicamente teniendo en cuenta la conectividad entre las dos áreas y los stocks de peces compartidos. Además, los resultados se han comparado con varios modelos ecológicos desarrollados en el mar Mediterráneo y el golfo de Cádiz y se han analizado varios escenarios de gestión. [...], [EN] A mass-balance model was developed to characterize the structure and functioning of the marine continental shelf and slope area of the Northwestern Mediterranean Sea, from the Toulon to Cape La Nao (NWMS model). The model has been built from previous applications of Ecopath with Ecosim in areas of the Northwestern Mediterranean (Gulf of Lions and South Catalan Sea). The model represented the ecosystem in the early 2000s, covered 45547 km2, and included depths from 0 to 1000 m. The study area was chosen to specifically account for the connectivity between these areas and the shared fish stocks. Furthermore, the results have been compared with several ecosystems models developed in the Mediterranean Sea and the Gulf of Cadiz and various management scenarios have been analyzed. [...], [FR] Un modèle d’équilibre de masse a été mis en place afin de caractériser la structure et le fonctionnement de la plateforme y talus continental de la méditerranée nord-occidental depuis Toulon jusqu’au Cap de Nao (Modèle de NWMS). Le modèle a été construit à partir des applications antérieures d’Ecopath with Ecosim dans des aires de la méditerranée nordoccidentale (Golfe de Léon et le sud de la mer catalane). [...]

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