POSTLARVAL AND JUVENILE MORTALITY IN A POPULATION OF THE EDIBLE COCKLE CERASTODERMA-EDULE (L) FROM NORTHERN BRITTANY

Survival and growth of newly settled cockles Cerastoderma edule in an intertidal population in the Bay of Morlaix (northern Brittany) were f ollowed from 1987 to 1991. The main settlement occurred throughout the autumn. After high post-larval mortality, the densities of juveniles became stabilized in late autumn or early winter. A fresh mortality pe riod started in winter and continued during spring parallel with an ac celeration in growth. The mortality rate declined to zero or near-zero values by early summer, at which time individuals had reached a lengt h of 10 to 12 mm. Several hypotheses concerning the causes of mortalit y during these periods are discussed.