ECOPHYSIOLOGICAL DETERMINISTIC MODEL FOR CRASSOSTREA-GIGAS IN AN ESTUARINE ENVIRONMENT

An ecophysiological deterministic model of growth, reproduction and in teractions between the bivalve and its estuarine environment was estab lished for the Japanese oyster Crassostrea gigas. The environmental va riables used in the model are: total particulate matter, particulate o rganic matter, particulate inorganic matter, chlorophyll, phaeopigment s, proteins, lipids and carbohydrates. Rates of clearance, filtration, ingestion, absorption and respiration along with efficiencies of rete ntion, selection and absorption are modelled with endogenous (dry weig ht of the animal, energy allocation between growth and reproduction) a nd exogenous variables (temperature, food quality and quantity). The m odel simulate the temporal evolution of two compartments: somatic and storage-gonad. Absorbed energy is allocated to soma up to a maximum so matic growth. This maximum decreases with age and never exceeds 0.02 g .d(-1).oyster(-1). Energy in excess is allocated to the storage-gonad compartment. The model identify storage and gametogenesis periods and correctly predicts spawning intensity. In this model, the oyster selec tively reject inorganic from organic particles, enriching the ingested ration. Within potentially nutritive particles, fewer particles conta ining phytopigments are rejected compared with detritic particles. Abs orption efficiency is represented as a function of organic content in the ingested ration. Microphytes are absorbed with an efficiency which fluctuates from 20 to 60%. The model predicts negative absorption for detritic material to take into account metabolic faecal losses. These s formulations provide information about the temporal evolution of the amount of microphytes and detritic matter biodeposited as pseudofaece s and faeces.