Data/hora: 01/06/2024 08:01:21

Provedor de dados: | 5
País: | France
Título: | Climate and pelagic fisheries in the Canary and Guinea currents 1964-1993: The role of trade winds and the southern oscillation
Autores: | Binet, D.
Data: | 1997
Ano: | 1997
Palavras-chave: | Pelagic fisheries; West Africa; Trade winds; Oceanic currents; Southern Oscillation.
Resumo: | Upwellings off the coasts of western Africa provide abundant but fluctuating marine resources. Sea surface temperature and wind stress, monitored by the ship-of-opportunity observation network, are compared to fishery statistics from 1964 onwards. In the Canary Current, off Sahara and Mauritania, upwellings are mostly wind driven. In the Guinea Current, off Cote d'Ivoire and Ghana, the link with local wind is very weak. In the southern Canary Current, two wind-intensification periods occurred in the early 1970s and from 1986 onwards. On each occasion, Sardina pilchardus landings were multiplied approximately threefold. During the first event, catches of species living at the periphery of the upwelling, Sardinella, Trachurus, Decapterus and Scomber, decreased slightly. During the second event, interrupted by some warming, catches of sardinelle increased, those of horse-mackerel decreased; mackerel landings increased only during the warm years. Sardine catches are correlated to the alongshore wind stress of the year (n-2), except during the very early months of larval life. Each wind stress increase induces an enrichment which favours larval survival, except just after hatching, when the adverse effects of turbulence and offshore advection prevail. In the part of the Guinea Current submitted to seasonal shoaling of the thermocline, a dramatic increase of the Sardinella aurita catch began at the beginning of the 1980s. Nevertheless, the SST warming trend does not indicate an intensification of deep-water uplift. Another hypothesis, based on the change of sign of the Southern Oscillation Index since 1976, is proposed. The tropical Atlantic would be in a long-term, warm, El Nino-like phase, with strengthened eastward circulations in the vicinity of the equator. Coastal surface and subsurface currents, linked to this eastward flux, would be intensified. Therefore, the number and/or the surface of eddies formed in these currents by Cape Palmas and Cape Three Points would be increased. Since sardinelle spawning occurs in these regions, which play the role of retention cells, enlargements of the turbulent structures would enable a larger number of larvae to thrive and sustain a larger population, according to the Sinclair hypothesis.
Tipo: | Text
Idioma: | Inglês
Identificador: | http://archimer.ifremer.fr/doc/00093/20390/18057.pdf
Editor: | Gauthier-Villars
Relação: | http://archimer.ifremer.fr/doc/00093/20390/
Formato: | application/pdf
Fonte: | Oceanolica Acta (0399-1784) (Gauthier-Villars), 1997 , Vol. 20 , N. 1 , P. 177-190