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Master Thesis

Dynamique spatio-temporelle de l’effort de pêche sur DCP des thoniers senneurs français dans l’océan indien

Abstract : Since the 1990’s, European purse seine fisheries targeting tropical tunas have globally increased their fishing power, mostly because of their increasing use of Fish Aggregative Devices (FAD), which have strongly modified their fishing strategies. In this context, the spatio-temporal patterns of the FAD fishing effort of French purse seiners were analyzed in the Indian ocean during 2000-2012 using a geostatistical approach. FAD fishing effort was defined as the local density of FAD fishing sets, and studied by quarter (3 months period), using logbook and VMS data. The analysis of 3 spatial indicators revealed an increase of the FAD fishing set density in the Somali area both at a local (0.5°x0.5° square) and regional scale (several squares). This increase is likely correlated to the increasing number of FADs deployed by the purse seiners in this area. The temporal variability of the spatial structure (variogram) was investigated using simulation techniques. For each quarter, spatial structures of fishing effort happened to be stable over time, but significantly different between quarters. The fishing area for each quarter was globally the same between 2000 and 2012, but some annual variations were detected, e.g. during the 2nd quarter (march-april-may) between 2003 and 2006: the fishing activity was lower in the Mozambique Channel and the spatial distribution of FAD fishing sets more patchy than usually. Finally, based on the hypothesis that a strong correlation exists between effort and local abundance, kriging maps of the FAD aggregated tuna spatial distribution were generated. The limitations and relevance of the work are discussed.
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Master Thesis
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Erwan Saulnier. Dynamique spatio-temporelle de l’effort de pêche sur DCP des thoniers senneurs français dans l’océan indien. Sciences agricoles. 2014. ⟨dumas-01096962⟩



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