Larval fish distribution in two different hydrographic situations in the Gulf of Cádiz

Ichthyoplankton assemblages and individual larval distributions of several mesopelagic and shelf-associated species were studied in two consecutive spring surveys in the Gulf of Cádiz (2001), covering both coastal and oceanic domains. The two surveys were characterised by markedly different hydrographical conditions, partly attributable to a shift from westerly to easterly winds. At the scale studied, larvae of coastal and shelf-dwelling species were always clearly separated from mesopelagic species, probably as a result of well-defined coastal-oceanic habitats related to a wide shelf and the prevailing currents. However, underlying these associations, short-term hydrographic changes induced by wind forcing seemed able to severely affect the distribution patterns of the early stages of some shelf-associated species. In particular, species like the European anchovy Engraulis encrasicolus were transported off the usual areas of maximal concentrations following a strengthened northwestern coastal countercurrent.