Food and feeding habits of Oreochromis niloticus (Linnaeus, 1757) in a tropical soda lake, lake Shaalaa, Ethiopia

Abstract

The food and feeding habits of Oreochromis niloticus in Lake Shalla, Ethiopia was examined by stomach contents analysis. Analysis of stomach revealed that 226 (65.9%) fish contained different food items, while 117 (34.1%) had empty stomachs. Non-empty stomachs had a variety of food items with phytoplankton, zooplankton, insect, detritus, nematodes and fish scales. O. niloticus mainly feed on phytoplankton and had phytoplanktivorous feeding habit. Bacillariophyceae (Nitzschia, Anomoeoneis, Navicula and Melosira) were identified as the most desired phytoplankton item. The prey items of O. niloticus differed among size classes (ANOVA, p< 0.05). The main prey items were zooplankton by the smaller-size class, and phytoplankton in fish of the larger-size class. Seasonal variation in the diet composition was evident (t-test, p< 0.05) and zooplankton, chironomids, nematodes, fish scales and detritus were important during the wet season, while phytoplankton predominates during the dry season. This study concludes that the food items and feeding habits depending on availability as influenced by season and fish size O. niloticus in Lake Shalla.