Effect Of Different Diets, Stocking Densities And Photoperiods On Juvenile Epinephel Us Malabaricus

In order to evaluate the effect of different diets, stocking densities and photoperiods on juvenile Epinephelus Malabaricus, three6-week feeding trails were conducted. In the first study, the juveniles(15±0.5g) were fed with raw fish (group A), formulated diet (group B), group C was fed with raw fish in the morning, formulated diet in the afternoon, and the effect of different diets on growth performance, digestive enzyme activitives, phosphatase activities and body composition of juvenile Epinephelus malabaricus were evaluated. In the second study, three hundred juveniles(15±0.5g) were randomly distributed in four experimental groups:G10(10fishes/tank,1.1kg/m3), G20(20fishes/tank,2.1kg/m3), G30(30fishes/tank,3.2kg/m3), and G40(40fishes/tank,4.2kg/m3), and the effect of stocking density on growth performance, plasma cortisol, blood glucose and activities of related enzymes of juvenile Elineophelelus malabaricus were evaluated. In the third study, the juveniles(15±0.5g)were reared under0L:24D light cycle(group D),24L:0D light cycle(group L) and Amb photoperiod(control group), respectively. The effect of different photoperiods on the growth, ingestion and lysozyme activity in liver of juvenile Epinephelus malabaricus was evaluated. The results showed:1. WG and SGR of group A were found to be significantly higher than those of other groups(P<0.05), and group C was slightly higher than group B(P>0.05). Gastric and intestinal proteinase activities of group A, and amylase activities of group B were the highest among the three groups, but no significant difference in lipase activities was observed among the experiment groups(P>0.05); alkaline phosphatase activities of group C were slightly lower than those of group A and slighter higher than those of group B(P>0.05), group A was significantly higher than group B(P<0.05), acid phosphatase activities of group A were significantly higher than those of other experiment groups(P<0.05). No significant difference in moisture content and crude ash content in whole fish was observed among the experiment groups, but significant difference was found in crude protein content (P<0.05), respectively, group A>group C>group B, however, crude fat content showed a contrary tendency and the difference was also significant(P<0.05).2. Weight gain (WG) and specific growth rate (SGR) of G10were the lowest among the experimental groups, and WG and SGR of G20were the highest. Feed conversion ratio (FCR) increased with the increase of density. No significant difference was observed in plasma cortisol levels between G30and G40(P>0.05), plasma cortisol levels of G10and G20were significantly lower than those of G30and G40(P<0.05), and plasma cortisol level of G10was the lowest. Similar trend was recorded in blood glucose levels. Glutamic pyruvic transaminase (GPT) activities of G30and G40were significantly higher than those of G10and G20; glutamic oxaloacetic transaminase (GOT) activities and lactic dehydrogenase (LDH) activities increased with the increase of the stocking density, total choline esterase (TChE) activities decreased with the increase of the stocking density. No significant difference in ratio of liver weight and body weight was found between G10and G20; G30and G40, neither. But, G30and G40were significantly higher than G10and G2o(P<0.05). Lysozyme activity showed a contrary tendency.3. Weight gain and lysozyme activity in liver of group D were slightly higher than that of control group(P>0.05), group D was significantly lower than other groups(P<0.05). Feed conversion ratio(FCR) of group D was significantly higher than those of group L and control group. Ratio of liver weight and body weight of group D was significantly higher than those of group L and control group(P<0.05).