Dynamiques des productions et des biomasses des huîtres creuses cultivées (Crassostrea angulata et Crassostrea gigas) dans le bassin de Marennes-Oléron depuis un siècle

The evolution of the production of cupped oysters is estimated on a century (1885-1985) with three different sources of data. The total biomass in culture is calculated from productions by knowing regularly the growing rate and the mortality rate of the populations of oysters. It appears that the efficiencies of the culture (P/B) decrease when the stock increase. The production reaches a plateau maximum of 40 000 tons whereas the stock goes on to growth up to 200 000 tons. This plateau correspond to the maximal capacity of production of the ecosystem limited by the trophic capacities of the bay. This work shows that without management of the cultivated oysters, the stocks tend to exceed the minimal biomass which is necessary to reach the maximal potential of production. If a regulation of the stock is applied it gives the folowing advantages decrease of the duration of the breeding cycle decrease of the chronics mortalities and decrease of the probability of epizooties