Dynamique des populations de Cerastoderma glaucum dans une lagune aménagée de la région d'Arcachon

Changes in demographic structure, growth and production of a population of Cerastoderma glaucum (Poiret, 1789) in an isolated brackish lagoon on the east coast of the Arcachon Basin (France) were investigated in 1976 and 1977. The early stages are present in filamentous algae or in plants (Ruppia maritima), while the 2 to 3 yr old cockles are on the bottom mud. Mortality results from bird (Laridae) predation and from dystrophic conditions which prevail in spring and summer. Migrations occur between areas with plants and unvegetated areas: Group 0 migrations are characterized by an increase in growth rate and P:B ratio of the cohorts of this group; they precede a natural recruitment or follow environmental stress. The distributions and migrations of these cockles are adaptive strategies to environmental factors in a system of brackish lagoons.