The food and feeding habits of the African catfish, Clarias gariepinus (Burchell), in Lake Babogaya, Ethiopia

Abstract

Demeke Admassu, Lemma Abera, Zenebe Tadesse

The food and feeding habits of the African catfish, Clarias gariepinus, in Lake Babogaya, Ethiopia, were studied from samples caught in each month during September 2005 to August 2006. Analysis of the stomach content (n=340) showed that the fish ingests a variety of items of plant origin, animal origin, detritus and sand grains. The items of plant origin were algae and macrophyte fruits and shoots whereas those of animal origin were crustacean zooplankton, insects, fish, mollusks, nematodes and fish eggs. The insects ingested by the fish were most diverse as they were sub-adult and adult stages belonging to seven taxa such as Hemiptera, Diptera and Odonata. The Nile tilapia, Oreochromis niloticus, was the only fish species ingested by the studied C. gariepinus. There were differences in the relative importance of the various items ingested by the fish. Thus, the frequency of occurrence of insects was the highest (82%), and this was followed by the frequency of occurrence of macrophytes and of zooplankton (each 60%), fish (26.8%) and fish eggs (16%). The numerically most important food were crustacean zooplankton (92.8%) followed by insects (5.31%), mollusks (0.95%) and O. niloticus (0.92%). Based on results from frequency of occurrence and numerical abundance methods, crustacean zooplankton, insects and fish (O. niloticus) are considered as the major food of the studied C. gariepinus. In contrast, the items of plant origin, detritus and sand grains were believed to be accidentally ingested while the fish was pursuing its prey. Therefore, C. gariepinus in Lake Babogaya is considered to have a carnivorous feeding habit. The study also found size-based and seasonal differences in the relative importance of the major food items. Thus, the frequency of occurrence method suggested that the fish feeds progressively less of zooplankton and insects, but more of O. niloticus as it grows larger/older. In addition, it feeds relatively more O. niloticus than the other major items in September 2005, and during February through to August (mainly in April and July). This is attributed to increased abundance of the prey following intensive breeding in the rainy seasons (February-April and JulySeptember). Likewise, monthly high frequencies of C. gariepinus with empty stomach were recorded during the rainy seasons in which time the fish breeds intensively. Thus, at that time the fish could be engaged more in spawning than in feeding activity.