Effects of salinity on digestive enzyme and alkaline phosphatase activity of young chum salmon (Oncorhynchus keta Walbaum).

Studies were conducted on the effect of salinity on protease,amylase,lipase and alkali phosphatase activity of young chum salmon(Oncorhynchus keta Walbaum)[body weight:(26.57±6.32) g,total length:(14.44±1.05) cm] digestive organs which were stomach,pyloric caeca,intestines and liver.Five different salinities were set which were 0,5,10,15 and 20 respectively,and fish in freshwater served as the control.The adaptative salinity experiments lasted for 130 days,and there were triplicates in each treatment.The results showed that stomach and intestinal protease activity of 30 days was higher than that of 130 days in young chum salmon.In 30 days,the activity of stomach protease and amylase had no significant difference(P 0.05) in five salinity groups,intestinal protease activity of 10 group was significantly higher than that of 20(P 0.05);in 130 days,stomach protease activity of 10 and 15 groups had significant difference(P 0.05),intestinal protease activity of 0 group was significantly higher than that of 5,10 and 20(P 0.05).The activities of pyloric caeca protease and amylase were the highest when the salinity was 0.The protease activity of liver was very low,but the activities of liver amylase and lipase were the highest in each salinity.The activity of alkaline phosphatase was the highest when the salinity was 10 in intestinal tissue of young chum salmon.