MODELING GROWTH AND FEEDING OF THE JAPANESE OYSTER CRASSOSTREA-GIGAS IN MARENNES-OLERON BAY (FRANCE)

A model simulating growth and feeding is presented for Crassostrea gig as and incorporates such physiological processes as filtration rate, p seudo-faeces production and ingestion, oxygen consumption and spawning . The only state variable is flesh weight. This model is designed to i ncorporate the effects of quantity and quality of food, temperature an d oyster dry weight. Comparison of simulation outputs with real data s howed that the model closely simulated the seasonal changes in weight over a two-year sample interval. This simulation confirms that oyster growth in Marennes-Oleron Bay is strongly regulated by the non-organic concentration in the seston. This latter factor dilutes the potential food for oyster and causes a large amount of food rejection in the fo rm of pseudo-faeces. Nevertheless, this regulation is lowered by the ' 'organic-inorganic'' sorting of particles which occurs during the pseu do-faeces formation. This sorting is found to enhance significantly th e organic ratio in the ingested food. Discrepancies between model and data are shown. The effects on feeding activity of endogenous control of gametogenesis and the physiological control of absorption by the qu ality of food would have to be incorporated in the present model in ol der to improve its reliability and its accuracy.