The food and feeding habits of the African catfish, Clarias gariepinus (Burchell, 1822), in Lake Langeno, Ethiopian Rift Valley

Abstract

The food and feeding habits of the African catfish (Clarias gariepinus) were studied in Lake Langeno, Ethiopia, from samples taken during April-October, 2000. Stomach content analysis (n=394) showed that the fish ingested a variety of items including algae, macrophyte parts, crustacean zooplankton, insects, fish and fish eggs as well as Hydracarina (water mites) and nematodes. The insects were most diverse and were subadult or adult stages belonging to at least eight taxa. The zooplankters were copepods (Mesocyclops sp), cladocerans (Daphnia, Diaphanosoma, Ceriodaphnia) and Ostracoda whereas the cichlid Oreochromis niloticus was the only fish species ingested. Frequency of occurrence was highest for insects (71.6%) followed by zooplankton (58.6%) and fish (19.8%). It was 7- 10% for macrophyte parts, detritus and sand grains, and below 1% each for Hydracarina and Nematoda. Results from frequency of occurrence, numerical abundance and gravimetric contribution showed that zooplankton, insects and fish are the major food items of C. gariepinus. Since the items of plant origin were believed to be accidentally ingested, the studied C. gariepinus is considered to have a carnivorous habit. The fish consumed progressively more O. niloticus but less zooplankton and insects as it grew in length. The contribution of fish to the diet of C. gariepinus was high during the season of high water level which was attributed to increased prey abundance due to spawning. There was also a concurrent high frequency of empty stomachs (%) during this time which may be due to the fish's engagement more in spawning activity than in hunting for prey. Analysis of prey to predator length ratios suggested that most of the studied C. gariepinus consumed O. niloticus that were 5-10% of their own length.

Keywords/phrases: Clarias gariepinus, Ethiopia, Food, Hydracarina, Lake Langeno, Omnivore