During one year, from March 1988 to June 1989, the intertidal population of Cerastoderma edule in the Bay of Saint-Brieuc, is investigated. Physiological measurements (ingestion, egestion, respiration and excretion) are monthly carried out in laboratory. We observe that reproductive metabolism influences the results. The energy budget of this cockle population, based on a biomass and production estimate for a 15 x 10 super(6) sq.m. area, is calculated and discussed.