Bilan énergétique de l'huître creuse (Crassostrea gigas) durant la période de forte croissance en mai en Baie de Marennes-Oléron (France)

Ecophysiological study was conducted on the japanese oyster (Crassostrea gigas) reared in Marennes-Oléron bay (France), during May 1992. Most of the somatic growth of the oyster occured during that month. The measurements were achieved from a removable laboratory stated in Le Chapus for 3 days at different tide level (coefficient of 49, 57, and 88). The food conditions were monitored through a computer with a continuous record of the turbidity during aIl the tidal cycle. In spite of an important variation between the food conditions in mean seston load, from 13,5 to 54,6 mg/!, the available organic matter ranged from 3 to 4,9 mg/l. The rate of organic matter in the water ranged 22 % to 9 %. The organic selection efficiency was significantly higher for the condition 3 compare to the others conditions. This indicated an improvement in the sorting of the oyster at lower organic content (58 %), compare to 30 % and 42 % for the condition 1 and 2. Furthermore, the best absorption rate of the food condition 2 and 3 (coef. 57 and 88), suggested a difference in food quality, probably associated to resuspension of the organic material from the bottom. So, the scope for growth was significantly different for the three conditions in a ratio of 1, 4 and 10, respectively for the conditions 1, 2 and 3 (coeff. 49, 57 and 88). These values ranged from 50 to 500 joules/h/g for three different days in may 1992.