Digestive enzyme activities in four diverse small indigenous fish species from Sareswar beel of Kokrajhar, Assam in Northeast India

Small indigenous fish species (SIFs) are important source of protein and micronutrients for the local population and hence considered as potential for aquaculture expansion. Pethia conchonius, Glossogobius giuris, Nandus nandus and Trichogaster fasciata are such SIFs found in Sareswar beel of Kokrajhar, Assam, India. This is an important beel with potential for development of fisheries in the region. Information on the food habit and digestive physiology are important in understanding the nutritional biology of a fish species essential for designing appropriate diet and feeding strategy for its successful culture. The present investigation aims to study and compare the feeding habit and digestive enzyme profile of these species. Relative gut length data suggested that P. conchonius and T. fasciata were herbivores, while N. nandus and G. giuris were omnivore and carnivore, respectively. Ga.SI varied in all the species (2.65 ± 1.39 to 4.66 ± 2.14) and the result indicated good or high feeding intensity in all the species. The highest amylase and lipase activity was observed in T. fasciata, and significantly lower activity was recorded in G. giuris and N. nandus, respectively. Pepsin was found to be highest in N. nandus while total protease was greatest in P. conchonius. Plasticity in the food intake in the natural environment seems to influence the enzyme activities. The present study has established vital information on the digestive enzyme properties and feeding nature of the four SIFs which may be useful in the development of suitable feed for their mass production for their successful culture.