Abstract:Effects of temperature on feed intake, growth and digestive enzyme activity of turbot Scophthatmus maximus L. were investigated in high stocking density of closed recirculation aquaculture system. Fish with a mean initial weight of 371.68 ±43.15 g were reared at four different temperatures (14℃, 16℃, 18℃, and 21℃) for 56 days. Three hundred and sixty fish were randomly allotted in four treatments with three replicates for each treatment in a stocking density of 14.20±0.48 kg/m2. The results indicated: (1)Within the temperature of 14～18℃, the feed intake of turbot increased with the increasing temperature, but when the temperature was 21℃, the average daily feed intake of this group was significantly lower than the other three groups(P<0.05). The average daily feed intake of group A, B, and C were significantly higher than D group by 25.65%, 32.26%, and 45.08% respectively (P<0.05). (2)Growth and survival rate of turbot increased first then decreased with the rising temperature. The weight gain rate of group A, B, and C was higher than group D by 75.23%, 91.05%, and 121.18% respectively, while the specific growth rate was 34.29%, 80.00%, and 102.86% respectively.(3)Pepsin activity of turbot first increased with the increasing temperature(14~18℃)and then significantly decreased when the temperature was 21℃(P<0.05). The pepsin activity of group A, B, and C was higher than group D by 116.74%,139.68%, and 202.64% respectively. There was no significant difference in intestinal lipase activity among four groups(P>0.05), while the intestinal amylase activity increased with the increasing temperature, and group D was higher than group C by 10.81%, significantly higher than group B by 59.74% (P<0.05)and significantly higher than group A by 115.79%(P<0.01). This study showed that the optimum temperature for feed intake, growth and digestive enzyme of turbot in high density closed recirculation aquaculture system was 16~18℃ and the feed intake rate was 0.52%～0.55% at the optimum temperature. Water temperature had significant effect on pepsin activity and intestinal amylase activity(P<0.05). According to this result, we suggest that the proper feeding rate is 0.57%~0.61% in actual farming for turbot with body weight of 300~600 g.
