Development of an intensive culture system for sea bass (Dicentrarchus labrax) larvae in sea enclosures

A system for the intensive production of sea bass larvae (Dicentrarchus labrax) in sea structures was developed between 1987 and 1994. In 1994, this system was used successfully for two larval rearing cycles (with 400 000 and 420 000 2-day-old larvae) at a fish farm. One hundred days after hatching the survival rate was 11%, and the mean weight of fish war; 2.5 g. The water temperature varied from 13.9 to 25.4 degrees C in the cylindro-conical enclosures (40 m(3)) which were set in the sea. The density of fish larvae at starting time was about 10 1(-1). Larvae were fed initially with Artemia nauplii (hatched out on land). Digestive content observations showed that they also fed on natural plankton in the enclosure. Weaning onto microparticles started when the mean length of the larvae reached 12 mm. Temperature variations were largely dependent on the water surrounding the enclosure but the chemical parameters inside were quite different from those of the sea. Many problems solved during the preliminary experiments are discussed, including the control of fouling, but contamination by predators or competitors is still a risk. The natural food web which develops in the enclosure, with the fish larvae as the main predators, seems to be an advantage for larval rearing. The use: of such an enclosure system, which is not expensive and is easy to set up at a farm, is discussed.