Physiologie de la maturation et de la ponte chez l'huître creuse Crassostrea gigas

The physiological ecology of the Pacific oyster Crassostrea gigas was studied using a conditioning delayed by temperature. Experiments were carried out on five batches and 2 year-classes classified into 6 maturation stages. The scope for growth concerning the stages N*5 and 6 was nearly zero while positive for early stages as well as for the post-spawning stage. Moreover, the 1 year-old oysters showed a significant lowered scope for growth (-110 J/h) compared to adult oysters (-14 J/h), therefore demonstrating the increased sensitivity of young oysters to stressful environmental conditions. By comparing the experimental results with the current models, developed on immature oysters, facilitates the model parameters spécifications during gametogenesis. For example, the respiration allometric coefficient shifted from 0.8 to 0.682. The increased demand for oxygen, correlated to gonadal weight increase was proportionally lower than a somatic growth. With regards to filtration rates, the differences between observed and predicted estimates were increased with meat weight increase and correlated with advanced gonadal stage. Therefore, the weight increase resulting from gametic production was not balanced by a proportionally increased filtration rate. The most significant differences were noted at temperature around 21*C.