CROSS-SHELF DISPERSION OF DOVER SOLE (SOLEA-SOLEA) EGGS AND LARVAE IN BISCAY BAY AND RECRUITMENT TO INSHORE NURSERIES

We studied the cross-shelf dispersion of Dover sole (Solea solea) eggs and larvae from the offshore spawning grounds to the coastal nurseries of Biscay Bay in 1987. Eggs and larvae were retained over the spawning grounds from late February to early April, consistent with the limited movement of satellite-tracked Lagrangian drifters at different depths in the water column. The distribution of the larvae coincided with maximum zooplankton abundance. In mid April, both sole larvae and drifters moved northward in response to wind forcing but the advection rate of the larvae was about one-third that of the drifters. No significant onshore advection of the pelagic stages was observed. No evidence was found for a behavioural selection of tidal currents by the pelagic larvae that could lead to onshore transport. Unless that behaviour developed after settlement to the bottom, cross-shelf diffusion of the pelagic stages would represent the main avenue of transport to the coastal nursery grounds. This dispersion strategy would imply that the vast majority of sole larvae fail to recruit to the bays and estuaries and are lost to the population.