THE OPERCULAR COMPLEX DEFORMITY IN INTENSIVE GILTHEAD SEA BREAM (SPARUS-AURATA L.) LARVICULTURE - MOMENT OF APPARITION AND DESCRIPTION

External morphology, head morphometry and osteology were used for earl y detection, description and heuristic study of the opercular complex abnormalities of intensively reared gilthead sea bream larvae (Sparus aurata). The first evidence of malformations were observed in larvae o f 6.1 mm total length (TL). The abnormalities were fully developed dur ing metamorphosis (11.0-22.0 mm TL), i.e., before the end of the hatch ery phase. Ln 81.4% of the abnormal fish, the problem was unilateral w ith similar right/left frequency. In 85.5% of the cases, it was associ ated with severe foldings and twists of the operculum and/or subopercu lum and rarely with an atrophy of these bones. The etiology, aquacultu re applications and research targets for the erasure of skeletal malfo rmations are discussed. (C) 1997 Elsevier Science B.V.