Data/hora: 12/06/2024 17:14:56

Provedor de dados: 	5	
País: 	France	
Título: 	Évolution de l'écosystème pélagique du Golfe de Gascogne pendant la période 1990-2003. Conséquences sur la capturabilité des espèces	
Autores: 	Villalobos, Hector.	
Data: 	2008-03-06	
Ano: 	2008	
Palavras-chave: 	Biscay Bay; Hydrological landscapes; Fishery; Atlantic mackerel; Atlantic horse mackerel; European sardine; European anchovy; Small pelagic fish; Acoustic image; Agregation pattern; School descriptors; Golfe de Gascogne; Paysages hydrologiques; Pêcherie; Maquereau; Chinchard; Sardine; Anchois; Petits poissons pélagiques; Image acoustique; Type d'agrégation; Descripteurs de bancs.	
Resumo: 	Several small pelagic fish species contribute remarkably to world catch. Their populations are, however, characterized by large biomass fluctuations strongly affecting fisheries. The fishing gears and methods used to capture small pelagics have evolved to exploit the highly developed shoaling behavior of these species. Hence, faced to modern fishing this gregarious behavior becomes a disadvantage for fish. Fish behavior may be affected by environmental conditions and by fishing, at the same time that behavior impacts fishing. In this study, we seek to characterize the aggregative systems of small pelagic fishes inhabiting the Bay of Biscay by analyzing "acoustic images", defined as the group of echoes (planktonic layers, shoals, isolated targets) detected on a transect section of a given length.  We analyzed the species composition, the spatial distribution and the evolution over time of acoustic images. We also studied the hydrological conditions of the bay, as well as the small pelagics French fishery in order to look for correlations between hydrology, commercial catch and fish aggregation patterns observed by acoustics. We observed the same species or group of species forming different types of aggregation according to habitat. Conversely, the same type of aggregation, associated with a particular habitat, can be produced by different species. The most notorious change observed during the studied period relates to small clupeoids aggregations in the vicinity of the Gironde estuary, whose structure evolved toward a greater fragmentation of shoals (a large number of small size detections) since 2000.  Concerning commercial catches, pelagic trawlers fishing in pairs mainly seek for anchovy in the coastal areas, single pelagic trawlers capture mackerel and horse mackerel in deeper waters while purse seiners target mostly sardine near their fishing ports. Because of the coarse spatial resolution of commercial fishing data and the effect of the application of an international fisheries agreement limiting the fishing activity of French pelagic trawlers during spring, only small correlations between captures and types of aggregation were observed.	
Tipo: 	Text	
Idioma: 	Francês	
Identificador: 	http://archimer.ifremer.fr/doc/2008/these-6083.pdf	
Editor: 	Université de Bretagne Occidentale	
Relação: 	http://archimer.ifremer.fr/doc/00000/6083/	
Formato: 	application/pdf