Abstract:
Studies of the food of introduced Nile tilapia, Oreochromis
niloticus (L.) with respect to size, habitat and season were
conducted between November 1998 and October 2000 in
Kenyan waters of Lake Victoria. Stomach contents of 1980
specimens collected by demersal trawl and seining were
analysed. Nile tilapia originally known to be herbivorous,
feeding mostly on algae has diversified its diet to include
insects, fish, algae and plant materials. The major diet of fish
<5 cm total length was zooplankton whereas bigger fish
included a wider range of food items in their diet. There was
spatial variation in diet with insects and algae dominating in
the gulf and open water habitats respectively. There was no
seasonal variation in the food items ingested and diel feeding
regime indicated that O. niloticus is a diurnal feeder. The shift
in diet could be due to ecological and environmental changes
in Lake Victoria, which have been associated with
changes in composition and diversity of fish and invertebrate
fauna, emergence and dominance of different flora including
water hyacinth Eichhornia crassipes (Mart.) Solms-Laub.,
and algae communities. The feeding habit of O. niloticus is
discussed in the context of changes occurring in the lake.