INFERENCES FROM THE HORIZONTAL DISTRIBUTION OF DAB LIMANDA-LIMANDA (L) AND FLOUNDER PLATICHTHYS-FLESUS (L) LARVAE IN THE SOUTHEASTERN NORTH-SEA

The horizontal distribution of dab, Limanda limanda L., and flounder, Platichthys flesus L., larvae in the southeastern North Sea was studied during the winter-spring period of 1992. Dab larvae comprised 51% of all fish larvae recorded and increased in abundance from February to late April, with a mean overall larval density of 38.8 ind.m(-2) during the study period. Flounder larvae comprised 10% of all fish larvae and were most abundant in late March with an average density of 12.5 ind.m(-2). Highest larval concentrations for both species were observed in waters off the west Frisian coast and in the inner German Bight, consistent with previously reported egg concentrations. Correlation analyses indicated similar distributions of early (I and II) stage larvae, but dissimilar distribution patterns in later (III and IV) larval stages. This is consistent with known spawning locations and postlarval habitats for the two species. Vertical migration is proposed as a potential mechanism that may explain the observed stage-specific horizontal distributions. Apparent differences in relative growth between two high-density centres suggested that larval dynamics may be different in these areas.