Etude de l'impact du stock d'huîtres et des mollusques compétiteurs sur les performances de croissance de Crassostrea ggias, à l'aide d'un modèle de croissance

A model coupling biological and hydrodynamical processes is used in order to study the influence of the amount of cultivated oysters (Crassostrea gigas) on growth performance in the Bay of Marennes-Oléron. The model is based on an energetic budget equation of a mean oyster and on a transport equation of particulate organic and inorganic matter through 12 spatial boxes. Sensitivity analysis is performed and allows computation of the impact of the distribution of oysters among the boxes on the growth performance of a mean oyster in each box. Il is shown that, mainly in the south of the bay, individual growth is affected by the increase in the stock. The same approach also shows that the response of individual growth to the amount of natural benthic filter-feeding populations is negligible compared with the preceding effect. Finally. the spatial variability of these responses is explained by the tidally induced residual circulation of the water throughout the bay from north to south. The water column is thus impoverished as the organic matter is filtered by the oyster populations.