Effet d'un substrat sur la survie et la croissance de la palourde Ruditapes decussatus en phase de pré-grossissement 2

Abstract

Studies conducted on the European clam show there is a high mortality during the pre-fattening phase 2, i.e. spat aged 20-35 days and between 0.5-4 mm in length. This mortality varies between 80-92% according to egg-laying and sample batches, but is always related to a rise in temperature, which may reach 30-33 degree C. The use of sand as substrate in the rearing sieves limited the mortality. The survival rates were between 40-93% for the sample batches of spat reared in the substrate, whereas they were only 10-20% for those reared without substrate. In fact, the mean length after 44 and 70 days of rearing was 4.66 plus or minus 0.59 and 5.73 plus or minus 0.90, respectively, with substrate as opposed to 3.49 plus or minus 0.73 and 5.43 plus or minus 1.30, respectively, without substrate. Furthermore, the percentage of spat 5.5mm or more in length varied from 63.1 to 92.5% in the pre-fattening samples with substrate, while it was between 47.3-64.4% for the pre-fattening samples without substrate. These preliminary samples need to be confirmed by tests with more replicates