REseau MOllusques des Rendements Aquacoles huitre creuse (REMORA) ; résultats des stations NATIONALES. Année 2003

The network IFREMER/REMORA quarterly follows each year 2 batches of Pacific cupped oysters Crassostrea gigas ("juveniles"= 1 year old; and "adults" = 2 years old) on various sites among the main French oyster areas. The network monitors 46 sites, including 7 new sites added in 2003 to the network. The network REMORA thus assess seasonal survival, growth and quality of cupped oyster oysters. It is a tool for trend estimations, ecosystem management and a reference frame for scientific studies. In spite of the heat wave of the summer, rearing performances in 2003 were close to the average inter annual 1994-2003 data. The rearing yield reached 1.8 for the adults. Summer mortalities remained limited, except for juveniles in some sites (Blainville, Morlaix, Ré, Marennes and Arcachon), and for adults in the Thau lagoon (due to an anoxic phenomena). The average growth gain was 30g (oysters reaching 60g in December) for the adults on estran and 25g for the juveniles. These data are close to the 1994-2003 average inter annual ones. Differences between "high" (Normandy, Thau) and "low" (Vendée, Pertuis Charentais) growth areas appear to be lower than usual, due to the tightening of the performances between the sites. The average meat index was 9.8 in December. All the batches reached at least the oyster label "Fines" (index > 6.5), and some batches (Normandy, Aber Benoit and Thau) reached the label "Speciales" (> 10.5). The Polydora index (0.3 on average) was slightly high compared to the former years, with larges differences between sites within the same area.