Approches de la capacite trophique des écosystèmes conchylicoles

The different methods for the estimation of the carrying capacity of cultivated area by oyster or mussel farming are presented gradually by order of complexity. The yield of production permit to follow if the adequation between the importance of the cultivated biomass and disponibility of food is realised. In another way, the study of the cultivated biomass and the annual production could be used for the building of global dynamic models showing the maximum of annual production that a bay can support. These approaches take for main hypothesis that the environment is constant. The study of the trophic relations for simulation of the growth rate of molluscs can be presented in function (i) of the level of complexity of the coupling between physical and biological model (ii) of the number of biological compartments. The physic is very often considered in a global approach, the ecosystem is represented by a large box where the residual fluxes and the mean residence time are the physical parameters. Some models are built with several boxes with the residual fluxes between the boxes, the transport of the particular food is realised by a model of advection and dispersion. For the biological laws, the classical laws of bioenergetics of the cultivated population are used with filtration, injestion, assimilation and respiration which permit to predict the growth rate. Generally, the biological compartments are not numerous when the physical models are complex and at the contrary certain biological models can have 10 or 30 biological boxes but with no physical approach or a very rudimentary one. But the model, coupling a realistic physic with the main biological compartments and their spatiotemporal variability, is not yet proposed. (Not controled OCR)