Occurrence of Dorsal Fin and Opercular Deformities and Their Effects on Body Weight in Asian Seabass

Asian seabass is an important aquaculture species. Dorsal fin and opercular deformities have been observed in hatcheries of this fish. However, it is unclear what causes these anomalies, and whether they affect growth performance. To quantify the occurrence of these anomalies, analyse their effect on growth, and trace their family origins, 8535 offspring generated from 13 independent mass-crosses were genotyped with 10 microsatellites. Dorsal fin and opercular deformities were recorded. Body weight at 90 dph were measured for each offspring. The occurrence frequencies of dorsal fin and opercular deformities were 2.30% and 2.16% respectively, with the former ranging from 1.38% to 5.16%, and the latter ranging from 1.38% to 4.84% for different batches of fish. These deformities significantly reduced the body weight, indicating that these deformities not only affected the appearance, but also decreased growth performance. Molecular parentage analysis revealed that fish with either dorsal fin or opercular deformities came from most of the families in each mass-cross, rather than from a few families or a few brooders, which suggests that heritabilities of these deformities might be low.