The diet composition, feeding intensity, gastrosomatic index and hepatosomatic index of the catfish, Mystus cavasius were studied for a period of one year i.e., from September, 2011 to August, 2012. The catfish, M. cavasius was feeding on the food material of plant origin as well as animal origin. The food material of plant origin i.e., phytoplankton belonging to Cyanophyceae, Chlorophyceae, Euglenophyceae and Bacillariophyceae. The animal material i.e, zooplankton belonging to Protozoa, Rotifera, Cladocera and Copepoda, insects, parts of insects and insect larvae belonging to Diptera, Trichoptera, Coleoptera and Hemiptera. The diet consisted of a broad spectrum of food items but phytoplanktonic group, Bacillariophyceae were the dominant constituting (28.02 %) followed by Cyanophyceae (16.87 %), Chlorophyceae (7.93 %) and Euglenophyceae (5.38 %). Among the macroinvertebtrates, insects and parts of insects were 8.77 % and insects larvae belonging to Diptera with 6.34 %, Trichoptera with 4.93%, mollusca with 3.80 %, Coleoptera (3.41%) Hemiptera (0.97%) and round worms (0.80 %) were in decreasing order whereas, amongst zooplankton, Copepoda were 8.08 % followed by Protozoa 1.85 %, Cladocera were 0.54 % and rotifer were 0.20 % had occupied successive positions. The mean percentage contribution of miscellaneous food group was (2.07 %). This fish has been categorised as eury-omnivorous fish. A pronounced high feeding intensity was recorded during December and January, when the gastrosomatic index was 5.40±0.15 and 5.43±0.10 respectively and stomachs were full and contained good amount of food while the feeding intensity was generally low during June, the gastrosomatic index (2.97±0.47). Four empty out of six stomachs were observed in the month of June. The highest hepatosomatic index value of M. cavasius was obtained in December as 3.55±0.17, while the lowest value was recorded in June (1.87±0.39). Gastrosomatic and hepatosomatic indices indicate clearly the feeding intensity and digestive capability of fish respectively
