Sea bass, Dicentrarchus labrax L. (= Morone labrax L. = Labrax lupus Cuvier and Valenciennes) is a carnivorous demersal fish relatively abundant in the Mediterranean Sea, as weIl as on the East Atlantic coasts of Europe and North Africa, in the North Sea, and the Baltic Sea. Sea bass live in coastal shallow waters and are common (mainly during juvenile stages) in brackish water lagoons or estùaries. They can attain 1 m (usually 0.5 m) in length and 15 kg in weight (average 4 to 6 kg). It is a highly valuable commercial fish in most Mediterranean countries and captive juveniles have been extensively cultured for many centuries in coastal lagoons. ", The first attempts to cultivate sea bass in intensive conditions started in France with Girin1.2 and Barahona-Femandes. 3 These authors used a clear water rearing technique in opposition to Barnabé4 who proposed a different technique with green water and low density of animaIs. The experiments were carried out from 1976 to 1978 and led to a definition of environmental rearing conditions and to a simplified food chain. Details on this technique, as weIl as on the biology and physiology of sea bass (larval development, growth, reproduction, etc.) can be found in Barnabé and Billard,5 and Barnabé. 6 However, the limits of this technique are illustrated by the variability of the results from both a quantitative and qualitative point of view. When, in 1982 to 1983, the clear water intensive technique was tested on a large scale, two "bottle-necks" were encountered: (1) Between days 20 and 30 (at 19°C) an abnormal behavior including whirling and loss of appetite with emission of white feces was observed and (2) anatomical abnormalities, including deformities of mandibular arcs and lordosis, was apparent in 80 to 90% of fish once they reached 20 mm in length. In this latter case, a correlation was found between the occurrence of lordosis and the lack of a swim bladder (Figure 1). These problems led IFREMER scientists to focus their efforts on developing new sea bass fry intensive rearing techniques. After 2 years of applied research devoted to rearing methods and 3 years of refinement and testing the techniques at a pilot scale, the problems have been solved. 7 ,8 A very reliable technique is now available for the first 45 d of culture. Only live food is used during the larval rearing period and then larvae are weaned onto a compound pellet. This second period (nursery) is still being worked out.