Decapod larval retention within distributional bands in a coastal upwelling ecosystem

Abstract

The spatial distribution and ontogenetic vertical migrations of decapod larvae in the northwestern Portuguese upwelling ecosystem were analyzed to explore the hypothesis of retention over the shelf and the related mechanisms involved. The sampled decapod crustacean larvae were retained on the continental shelf along 3 meridional bands parallel to the coast, independent of larval phase duration or taxonomic group. All larval stages belonging to inner shelf or estuarine species were found close to the shore, mainly restricted to a 10 km wide band. The larvae of shelf species were mainly distributed in the middle of the shelf. However, some of these species were widely distributed over the shelf, whereas others were more abundant in the northern or southern transects (as a consequence of the advection of a warmer water mass from the south). The outer shelf band included larvae from slope species. This distribution pattern (i.e. in bands) corroborates observations from other coastal upwelling systems and results from the relationship between larval behavior and local oceanographic processes. Ontogenetic vertical migration behavior was evident for almost all the taxa analyzed, in which the older stages (last zoeal stages, decapodids and megalopae) were usually found in deeper strata of the water column. © Inter-Research 2014.