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Master Thesis

Impact de la pêche thonière à la senne sur les communautés pélagiques de l’océan Atlantique tropical et de l’océan Indien : comparaison de la pêche sous dispositifs de concentrations de poissons et sur bancs libres

Abstract : FAD-fishing discards 10% of its capture versus 3% in FSC-fishing. In the 114 taxa observed between the Atlantic and the Indian ocean a total of 68 taxa were common to both oceans, 13 exclusive to the Atlantic and 34 to the Indian ocean. To avoid species identification issues, a total of 22 taxonomic groups were developed. The richness, the diversity and the equitability analysis conducted on those 22 groups showed that these index were higher under FAD and in the Indian ocean. At the same time, trophic and length class analysis revealed that the mean trophic level of the bycatch was higher on FSC than under FAD and length class were slightly smaller under FAD. FAD fishing catches smaller individual of a larger portion of lower trophic level. The biomass-size spectra constructed in this study revealed significant difference between fishing modes and oceans. Fishing under FAD impact more marine communities and a larger part of the ecosystem. Most of silky sharks caught by the french tuna purse-seine fishery are captured under FAD and are mainly dominated by immature individuals. The model showed a strong spatial and temporal effect on the silky sharks bycatch level. The Somalian coast and the inner Guinean Gulf are hotspots of silky sharks bycatch and could be protected in order to reduce the capture of this species. The results of our multispecific model have shown spatial and seasonal pattern characterised by high and low value of Simpson diversity index and could be used for an ecosystem based fishery management for tuna purse-seine fisheries.
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https://dumas.ccsd.cnrs.fr/dumas-01267161
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Charlie Widehem. Impact de la pêche thonière à la senne sur les communautés pélagiques de l’océan Atlantique tropical et de l’océan Indien : comparaison de la pêche sous dispositifs de concentrations de poissons et sur bancs libres. Sciences du Vivant [q-bio]. 2015. ⟨dumas-01267161⟩

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