Evolution saisonnière de la filtration de bivalves intertidaux dans des conditions naturelles

The study of cultivated ecosystems, once the trophic capacity ha! been determined and the molluscan stocks estimated, requires a knowledge of the evolution of the seasonal consumption of food by molluscs in natural conditions. For Crassostrea gigas, Mytilus edulis, Cerastoderma edule, Ruditapes philippinarum, the amount and quality of food have no effect on the filtration rate, except for the high load of mineraI seston. First an increase of the filtration rate was shown for Mytilus edulis and Cerastoderma edule at the end of winter and beginning of spring. Moreover Crassostrea gigas and Ruditapes philippinarum have shown no increase or only a small summer one. This evolution did not seem to be linked with the environmental conditions (temperature, chlorophyll and pheophytin, mineral seston), but seemed related to the reproductive cycle of molluscs. The Intake of energy resulting from filtration is due both to the amount of potential food and to the needs of molluscs.