Variation of larval fish distributions associated with variability in the location of a shelf-slope front

This study examines the extent of the interaction between the short-time-scale variability in the location of the shelf-slope salinity front and the species composition and abundance of larval fish in the NW Mediterranean. Three extensive cruises were carried out during spring (May and June 1992), a season characterized by high mesoscale variability. Variations in the position of the shelf-slope front were correlated with large changes in the distribution and abundance of fish larvae. In the 3 surveys, offshore dispersal of fish larvae of shelf-dwelling species appeared to be limited by the geographical position of the front. When the frontal structure was detected over the shelf, the distribution of larvae of shelf-dwelling species was confined to the coastal side of the front, while larvae of mesopelagic fish species were located on the oceanic side. When the front was detected over the slope, it did not act as a barrier separating the larval distributions of shelf and oceanic species but instead limited the offshore extent of the larval distribution of shelf species.