Bone development of the skull, pectoral and pelvic fins in Seriola rivoliana (Valenciennes, 1833) larvae.

Skull, pectoral and pelvic fin bone structures in longfin yellowtail Seriola rivoliana were studied from 3.43 ± 0.15 to 16.20 ± 0.73 mm standard length (SL) specimens. The S. rivoliana skull started to mineralize with the appearance of the parasphenoid and maxillary by 3.43 ± 0.15 mm SL at the neurocranium and jaw regions, respectively. The first pectoral structure to mineralize was the cleithrum at 3.75 ± 0.14 mm SL shortly followed by the supracleithrum and posttemporal. The pelvic fin started by 6.16 ± 0.32 mm SL with the spine and continued with the soft rays and basipterygium. The present study determined the onset of the skull, pectoral and pelvic fin mineralization. These results might be used as a reference for future studies in S. rivoliana or related species.

Occurrence of skeletal deformities and osteological development in red porgy Pagrus pagrus larvae cultured under different rearing techniques.

The present study describes the osteological development and the occurrence of skeletal deformities in red porgy Pagrus pagrus larvae in relation to the intensification of the rearing system. Eggs obtained from natural spawning were cultured under two different rearing systems: intensive (100 eggs l⁻¹) in 2000 l and semi-intensive (mesocosm) system (5 eggs l⁻¹) in 40,000 l conico-cylindrical tanks. Fish samples were periodically collected along the development from hatching to juveniles at 95 days post hatching (dph). Osteological development, meristic counts and the presence of skeletal deformities were evaluated. Despite the external appearance of the juveniles being similar to wild standards, X-ray studies revealed a high number of fish (semi-intensive: 37·8%; intensive: 45·5%) with skeletal deformities. Regardless of the rearing system, no significant interaction was found between the per cent of the most common deformities, axial deviations (lordosis and presence of fused vertebrae). Cranial deformities and kyphosis incidences, however, were significantly higher in intensively cultured P. pagrus. Also, the fused vertebrae in these fish were located mainly in the caudal area instead of pre-haemal area for semi-intensively reared P. pagrus. Moreover, a significant interaction was found between the total number of vertebrae and the type of rearing system used; fish from the intensive system showing a higher number of fish with an extra vertebrae (10 abdominal + 15 caudal). Present results suggest a relationship among feeding sequence, osteological development and deformity incidence and location in P. pagrus larvae.