Effects of Different Salinities on Growth, Feeding Performance and PlasmaCortisol Level in Hybrid TGGG (Tiger Grouper, Epinephelus fuscoguttatusxGiant Grouper, Epinephelus lanceolatus) Juveniles

摘要

The hybrid TGGG, tiger grouper Epinephelus fuscoguttatusx giant grouper, Epinephelus lanceolatus has a high resistancetowards extreme conditions due to its genetic improvement. This study investigated the effects of different salinities ongrowth, feeding performance and plasma cortisol level in TGGG juveniles. The TGGG juveniles were acclimatized andsubjected to 7 different water salinities at 5, 10, 15, 20, 25, 30 and 35 part per thousand (ppt) for30 days. The survivalrate, growth rate and feed conversion ratio (FCR) were calculated at 10-day intervals. The optimum salinity is 10 to 20 pptbased on higher growth performance in terms of the final weight (g= gram), average daily growth (ADG=g/f/d,gram/fish/day), and specific growth rate (SGR=%/d ,percentage/day) observed at 10 ppt (19.20-0.63 g, 0.32-0.01g/f/d and 2.69-0.06%/d), 15 ppt (18.52-1.55 g, 0.31-0.04 g/f/d and 2.80-0.22%/d) and 20 ppt (18.17-1.04 g, 0.30-0.03g/f/d and 2.74-0.23%/d). Besides, the optimum salinity was also determined based on the lower feed conversion ratiovalue at 10 ppt (1.24-0.04), 20 ppt (1.26-0.14) and 15 ppt (1.30-0.20). This study shows that high salinity at 35 ppt,(14.38-2.11 g, 0.19-0.02 g/f/d and 1.95-0.40%/d) and 30 ppt, (15.31-0.68 g, 0.21-0.02 g/f/d and 2.06-0.17%/d) leads topoor growth performance of TGGG juveniles. Plasma cortisol levels in 5 ppt (56.50 nmol/L), 15 ppt (19.31 nmol/L) and 35ppt (33.54 nmol/L) were significantly higher compared to those in 10, 20, 25 and 30 ppt. On a broad scale, this study isvery significant in providing useful information for the TGGG to increase mass production and promote economic growth.