Effects of Salinity on the Growth, Survival and Stress Responses of Red Spotted Grouper Epinesphelus akaara and Hybrid Grouper E. akaara x E. lanceolatus

摘要

In this study, we crossbred Epinephelus akaara and E. lanceolatus to produce a hybrid grouper with faster growth and adaptation to domestic aquaculture environments. The plasma Cortisol and glucose levels and osmoregulation (stress response indicators) of the hybrid grouper, E. akaara ￡ x E. /anceolatus J1, were investigated under several salinity levels (32, 24, 16, and 8 psu). The body lengths and weights of E. akaara (8.2 ± 0.1 cm, 8.3 ± 0.4 g) and the hybrid (8.6 ±0.1 cm, 10.0 ± 0.4 g) weresimilar at the start of the experiment, but were significantly different at the end of the experiment. Juveniles of both E. akaara and the hybrid showed greater weight gain, specific growth, and feed conversion rate (FCR) under low salinity of 16 psu. Under the 8 psu treatment, the juvenile E. akaara all died, while the hybrid juveniles survived. Plasma Cortisol levels were not affected by lower salinity in both species. The above results indicate that the hybrid is more tolerant of low salinity than isE. akaara, although both species exhibited higher growth and FCR at 16 psu, lower than the salinity of natural seawater. Thus, juveniles of both E. akaara and the hybrid can be more effectively cultured in brackish areas or waters with salinity lower than that of seawater.