Effets de l'apport de phytoplancton (Skeletonema costatum) sur la croissance et les variations de la composition biochimique de la palourde japonaise Ruditapes philippinarum cultivée en marais

A bulk production of phytoplankton (Skelelonema costatum) has been obtained in concrete tanks from saline groundwater. This was used in various concentrations to feed an intensive cultivation of the Manila clam (Ruditapes philippinarum) in ponds. No difference was observed in growth rates of molluscs, with food concentrations between 31 to 126 µg/l Chl a. However, the growth rates obtained from March to November with a food supplement were 1.5 times higher than those observed in the traditional, extensive cultivation. The biomass doubled and the increase in flesh dry weight was 2.5 times higher. The condition index reached a value of 100 in the intensive cultivation. During growth, the proximate composition analysis revealed that the lipid and carbohydrate contents of the clams were higher when they were fed on Skeletonema costatum, while protein contents remained stable.