Effects of Salinity on Growth and Energy Budget of Juvenile Cobia, Rachycentron canadum

摘要

The effects of salinity on the growth and energy budget of juvenile cobia, Rachycentron canadum, were evaluated. Triplicate tanks with ten fish per tank (initial weight 17.58 +/- 0.26 g/fish, mean +/- SD) reared at salinities of 5, 10, 15, 20, 25, 30, and 35 ppt were fed with fresh squid to satiety for 15 d. Results indicated that there were no significant differences in daily ration level in wet weight (RLw), dry weight (RLd), and energy (RLe) of the fish. There were also no significant variations in daily fecal production (f(e)) and apparent digestibility coefficient of energy (ADC(e)) among salinity treatments. Specific growth rates (SGRs) in wet weight (SGR(w)), dry weight (SGR(d)), and energy (SGR(e)) showed domed curves relative to salinity. Quadratic regression analyses of SGR(w), SGR(d), and SGR(e) against salinity indicated that the optimal salinity for maximal growth of juvenile cobia was 29.9, 29.9, and 28.5 ppt, respectively. Similar to the trend of SGR, food conversion efficiency for juvenile cobia in wet weight (FCEw), dry weight (FCEd), and energy (FCEe) increased with the increases in salinity, maximized at 30 ppt, and then decreased when salinity reached 35 ppt.