Digestive enzyme and alkaline phosphatase activities during the early stages of Silurus soldatovi development.

To provide a theoretical basis to improve the survival and growth rate and optimize diet of sheatfish (Silurus soldatovi), the activities of certain digestive enzymes and alkaline phosphatases were investigated during larval development of one-ten day old individuals. Results indicated that sheatfish larva (~ three days after hatching) had high levels of alkaline protease activity, which peaked at five days old and dipped by eight days old, although the trend was generally upward. Acid protease activity at one-eight days old was low, after which it increased rapidly. Amylase activity reached the highest value at five days old, after which it began to decline. Lipase activity fluctuated markedly and showed two peaks at three-four days old and six-eight days old. Larval digestive enzyme activity and alkaline phosphatase activity were higher when fed live food than when fed an artificial diet. Throughout the early development process, alkaline protease activity was higher than acid protease, alkaline protease and amylase specific activity decreased significantly for eight-day-old transition larvae, while acid protease activity increased rapidly. These results indicate that the changes in digestive enzyme activity were relevant to digestive function conversion during fish larvae development. Alkaline phosphatase activity showed an upward trend over the first ten days of life, which indicated that the gastrointestinal function of sheatfish improved gradually.