¿Es determinante la dinámica en los niveles superiores de la columna de agua sobre la abundancia y distribución de peces en el mar Cantábrico?

Abstract

Since 1993, successive bottom-trawl and hydrographic surveys have been carried out along the continental shelf of the cantabrian sea in summer and autumn. The existence of defined aggregations of recruits of demersal fishes in localized recruitment areas ranging 25-30 km diameter has been observed. Yearly variations of density of re 55 J. Gil y R. Sánchez ¿Es determinante la dinámica en los niveles superiores...? cruits within these aggregations, instead of area size variations, have also been observed, although eventual vanishing of such structures was observed when density of aggregations fall below the detection limit. Concerning the oceanographical settings, the main external driving agents that configure the annual scenario have been identified: the Poleward Current (PC) and the seasonal wind regime that sets up the summer upwelling. The hypotheses put forward propose that: (i) the PC conditions zonal and meridional transports of biological material at the timing of spawning; (ii) the wind regime modules the retention of eggs, larvae and post-larvae within mesos cale structures as well as provides the base of fertilization that supports the trophic chain in which the preand recuits are after recruitment. The presence of anticyclonic eddy structures of approximately the same size as the recruits' aggregations in years of good recruitment, and that are within the mesoscale bounds for the stratification and latitude parameters of the Cantabria sea, seem to valid both hypotheses. These eddies surround the upwelling front and coincide with areas were aggregation of recruits is likely. The present paper presents the relationships between the formation and drift of such mesoscale structures and the processes that determine the recruitment of demersal fishes along the suthern Bay of Biscay. 1.