Food and Feeding Habits of the Red-Belly Tilapia (Tilapia zillii Gervais, 1848) (Pisces: Cichlidae) in Lake Ziway, Ethiopia

Food and feeding habits of T. zillii were studied from 572 fish samples collected from April to May 2011 (dry season) and July to August 2011 (wet season) from Lake Ziway. Stomach content analysis was conducted using frequency of occurrence and volumetric methods of analyses. Macrophytes, detritus and phytoplankton were the dominant food categories occurring in 94.9%, 94.2% and 82.5% of the total stomachs examined and constituting 45.2%, 29.4% and 16.8% of the total volume, respectively. The contributions of insets, nematodes, zooplankton and ostracods were relatively low. Macrophytes (50.4%), phytoplankton (21.8%) and detritus (18.5%) constituted the bulk of the food volume during the dry season. In the wet season detritus (40.8%), macrophytes (37.8%), phytoplankton (12.5%) and insects (6.5%) contributed the bulk of the food categories consumed. Phytoplankton, detritus and insects were important food categories of juveniles (5.0-9.9 cm TL) whereas macrophytes, detritus and phytoplankton were important food categories of adults. The importance of phytoplankton, detritus and insects declined with size of fish whereas the importance of macrophytes and nematodes increased with fish size. Based on the results of the stomach contents it was concluded that the species is an herbivorous feeding mainly on macrophytes, detritus and phytoplankton. The contribution of animal origin food was low.