The Salinity Adaptation And Nutrition Regulation Of Epinephelus Malabaricus

Effect of low salinity stress on activities of digestive and anti-stress enzymes, and survival rate of juvenile Epinephelus malabaricus was studied through reducing the salinity of the sea water gradually, and the tolerance range of salinity to juvenile fish was discussed. And the effect of three dietary supplementations of green additives (small peptide, bacillus and inulin) to the growth, digestive function, anti-stress ability and immune function of Elineophelelus malabaricus were studied. We hope our work will provide reference for the future culture of Epinephelus malabaricus.The first experiment was designed to investigate the effect of low salinity stress on the digestive enzymes, anti-stress enz-ymes and the survival rate of juvenile fish. The larva were reared in the water with the salinity concentrate of28.23%o,22.56%o,17.57%o,12.67%o and7.71‰for three days respectively. The results showed that the protease and amylase activities significantly decreased with the decreasing of the salinity gradient (P<0.05) both in stomach and intestin. The activity of SOD was increased, while CAT, GSH-Px descended with the increasing of the salinity in liver, muscle and kidney. In addition, the death were appeared when the salinity were12.67%o, and all the juvenile fish were died within12h when the salinity were7.71‰. Hence, the digestive enzymes and anti-stress system of juvenile Epinephelus malabaricus were effected seriously by low salinity stress and would affect the healthy growth of juvenile fish.Secondly:A60days feeding trail was conducted to evaluate small peptide,bacillus and inulin as green additives on growth performance,gastrointestinal digestive enzymes activ-itives and other enzymes activities associated with oxidative stress in juvenile fish. The juveniles were fed with formulated diet which had been added with2%small peptide (group Ⅱ),0.01%bacillus(group Ⅲ),0.2%inulin(group IV),0.01%bacillus and0.2%inulin (group V), group Ⅰ was control group with no additives. The results showed:1) the growth rates of group Ⅱ were found to be significantly higher (p<0.05) than those of the control;2) gastric and intestinal proteinase enzymes activities of group II were significantly higher(p<0.05) than those of the control, intestinal lipase activities of group Ⅱ,group III and group V were significantly higher than those of the control;3) SOD activities in liver of group Ⅱ was significantly higher (p<0.05) than those of the control, CAT activities in blood of group Ⅱ and CAT activities in liver of group V were significan-ly higher(p<0.05) than those of the control; MDA activities in blood of group V were sign-ificantly low;4) LDH activities in liver and Na+,K+-ATPase activities in gill of group Ⅱ and group V were significantly higher(p<0.05) than those of the control. Hence, dietary supplementation of green additives, especially the bacillus, facilitate the growth, digestive function, anti-stress ability and immune function of Epinephelus malabaricus.The third experiment was designed to evaluate small peptide, bacillus and inulin as green additives on gastrointestinal digestive enzymes activitives and other enzymes acti-vities associated with oxidative stress in low salinity water. The juveniles were fed with formulated diet which had been added with2%small peptide(group Ⅱ),0.01%bacillus(group Ⅲ),0.2%inulin(group IV),0.01%bacillus and0.2%inulin(group V), group I was control group with no additives.All the juveniles were first reared in waters of28.5%o salinity for60days, then salinity was reduced to13.5%o for one week. The results showed:1)gastric and intestinal proteinase enzymes activities of group Ⅱ, intestinal amylase activity of group Ⅱ and group V were significantly higher(p<0.05) than those of the control;2) CAT activities in liver of group Ⅱ and group V were significantly higher(p<0.05) than those of the control;3) LD content and LDH activities in liver of group Ⅱ, group IV and group V were significantly higher(p<0.05) than those of the control and group Ⅲ, AKP activities in liver of group V were higher than other groups;4) Na+,K+-ATPase activities in liver of group Ⅱ were significantly higher(p<0.05) than those of the control, Na+,K+-ATPase activities in gill of group Ⅱ and group IV were significantly higher (p<0.05). Hence, dietary supplementations of green additives facilitate digestive function, anti-stress ability and immune function of Epinephelus malabaricus.