The opercular complex deformity in intensive gilthead sea bream (Sparus aurata L.) larviculture. Moment of apparition and description

Abstract External morphology, head morphometry and osteology were used for early 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 of 6.1 mm total length (TL). The abnormalities were fully developed during metamorphosis (11.0–22.0 mm TL), i.e., before the end of the hatchery phase. In 81.4% of the abnormal fish, the problem was unilateral with similar right/left frequency. In 85.5% of the cases, it was associated with severe foldings and twists of the operculum and/or suboperculum and rarely with an atrophy of these bones. The etiology, aquaculture applications and research targets for the erasure of skeletal malformations are discussed.