THE FOOD AND FEEDING HABITS OF THE AFRICAN CATFISH, CLARIAS GARIEPINUS (BURCHELL, 1822) (PISCES: CLARIIDAE) IN LAKE HAWASSA AND SHALLO SWAMP, ETHIOPIA

Feeding habits of the African catfish Clarias gariepinus (Burchell, 1822) was studied based on 252 and 211 fish specimen collected from Lake Hawassa and Shallo swamp during dry and wet months of 2011. C. gariepinus in Lake Hawassa consumed insects (21% by volume), fish eggs (18.3%), fish (18.1%), gastropods (14.4%), macrophytes (13.6%), detritus (8.4%), zooplankton (2.6%), phytoplankton (1.7%), ostracods (0.7%), nematodes (0.5%) and fish scales (0.5%). In Shallo swamp, the fish mainly fed on macrophytes (31.7% by volume) and detritus (31.5%). Insects (12.2%), amphibians (9.5%), zooplankton (5.3%) and phytoplankton (4.9%) had also some contribution, while fish eggs, gastropods, ostracods, water mites and nematodes had insignificant contribution to the diet. Seasonal variation in the diet of C. gariepinus was slight in both habitats. Ontogenetic dietary shift was observed in Lake Hawassa. Smaller size C. gariepinus ( 45 cm TL) tended to filter-feed more on zooplankton. All size groups of C. gariepinus in Shallo swamp mainly fed on macrophytes and detritus. Generally C. gariepinus in both habitats fed on food of plant and animal origin albeit in varying proportions, and the fish can be considered as omnivorous in its feeding habit.