Effects of salinity on digestive enzyme activity and diurnal variation of digestive enzyme activity of young Yellowfin black porgy Sparus latus

Studies were conducted on the effect of salinity on digestive enzyme activity and the diurnal variation of digestive enzyme activity of young yellowfin black porgy (Sparus Latus).The yellowfin black porgy was cultured at six different salinity(5,10,15,20,25,30).Test results indicated that the activities of protease and lipase were the highest when the salinity was 25,but the activity of α-amylase was the highest when the salinity was 20.The average digestive enzyme activity at the salinity of 20,25 and 30 was much higher than that at the salinity of 5,10 and 15.The study on the diurnal variation of digestive enzyme activity of yellowfin black porgy showed that the highest activities of protease,α-amylase and lipase appeared at 14∶00,20∶00 and 18∶00,respectively,while the lowest activities of protease,α-amylase and lipase appeared at 12∶00,10∶00 and 6∶00,repectively.