Studies on the natural food of major, common and some chinese carps as influnced by fertilization in composite culture practices

Natural food components were analyzed for Catla catla, Labeo rohita, Cirrhinus mrigala, Cyprinus carpio, Hypophthalmichthys molitrix and Ctenopharyngodon idella in 6 composite culture ponds, which were fertilized with broiler manure. The natural food examined and defined was collected both from guts of fish sampled and from pond water. The proportional amount of phytoplankton found in guts of Catla catla, Labeo rohita, Cirrhinus mrigala, Cyprinus carpio, Hypophthalmichthys molitrix and Ctenopharyngodon idella was 80-90 %, 70-80 %, 60-70 %, 60-80 %, 35-90%, 28-75%, respectively. The parallel zooplankton values were 10-15 %, 25-30 %, 30-40 %, 20-40 %, 20-30%, 25-45 %, respectively. In ponds stocked with these 6 fish species, the proportional amount of phytoplankton in the pond water was 10-20 %, 25-35 %, 30-40 %, 45-55 %, 15-25 %, 10-20 %, respectively. This demonstrates empirically the inverse relationship between the type of plankton preferentially consumed by a given fish and the predominant plankton type present in ponds stocked with that fish. The mechanism of this preferential feeding is presumably associated with the diameter of the filtering net meshes of the gills of these fishes