Author(s): Amni raihan othman, Gunzo Kawamura, Shigeharu Senoo, Ching Fui Fui
The hybrid TGGG, tiger grouper Epinephelus fuscogut tatusx giant grouper, Epinephelus lanceolatus has a high resistance towards extreme conditions due to its genetic impro vement. This study investigated the effects of diff erent salinities on growth, feeding performance and plasma cortisol lev el in TGGG juveniles. The TGGG juveniles were accli matized and subjected to 7 different water salinities at 5, 10, 15, 20, 25, 30 and 35 part per thousand (ppt) for 30 days. The survival rate, growth rate and feed conversion ratio (FCR) w ere calculated at 10-day intervals. The optimum sal inity is 10 to 20 ppt based 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±0.6 3 g, 0.32±0.01 g/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±0.03 g/f/d and 2.74±0.23%/d). Besides, the optimum sali nity was also determined based on the lower feed co nversion ratio value 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 sal inity at 35 ppt, (14.38±2.11 g, 0.19±0.02 g/f/d and 1.95±0.40%/d) an d 30 ppt, (15.31±0.68 g, 0.21±0.02 g/f/d and 2.06±0 .17%/d) leads to poor growth performance of TGGG juveniles. Plasma c ortisol levels in 5 ppt (56.50 nmol/L), 15 ppt (19. 31 nmol/L) and 35 ppt (33.54 nmol/L) were significantly higher compar ed to those in 10, 20, 25 and 30 ppt. On a broad sc ale, this study is very significant in providing useful information fo r the TGGG to increase mass production and promote economic growth.