Abstract
The digestion process in fish is a complex phenomenon and is accomplished with the help of both endogenous and exogenous enzymes. A wide range of enzymes have been reported in fish and their secretion and concentrations highly depend on feeding habits, gut structure and environmental conditions. In this present investigation, we have demonstrated the activity of two endogenous enzymes (protease and amylase) in four economically important air-breathing fish species (Clarias batrachus, Channa punctatus, Anabas testudineus and Heteropneustes fossilis) at different seasonal temperatures. Our results demonstrated that protease activity was higher in all fish during the month of May, followed by September and December. It was also detected that enzyme activity was higher in the hindgut region (HG) compared to the foregut (FG), which suggests that HG is more active in digestion compared to FG. The optimization of feeding efficiency in aquaculture industries is very important, as the cost of feed is high and its availability is also limited. The information presented may be of importance when developing optimized diets and feeding regimes for the species considered.