Feeding selectivity of wild and pond-cultured Nile tilapia Oreochromis niloticus in the Lake Victoria basin in Mara, Tanzania

Abstract

A comparison of feeding selectivity of wild and pond-cultured Nile tilapia Oreochromis niloticus was conducted in 2008. Water and fish samples were collected in Shirati Bay, Lake Victoria, and from fish ponds in Tarime district using a La Motte water sampler and seine nets, respectively. Cyanophytes were abundant and were the major diet component of fish in both habitats. Chlorophytes were selected by pond fish. Bacillariophytes were selected by fish in both habitats, despite their low abundance in pond water. Astrionella sp. and Rhopalodia vermicularis (bacillariophytes) and Peridinium sp. (dinophyte) were selected by fish in both habitats. Astrionella sp., Aulacoseira nyassensis, Navicula sp. and Rhopalodia vermicularis (bacillariophytes) were the species most selected by lake fish, whereas Ankistrodesmus falcatus (chlorophyte), Lyngbya circumcreta (cyanophyte) and Nitzschia acicularis (bacillariophyte) were the species most selected by pond fish. These results suggest that Nile tilapia is a selective feeder. It is therefore recommended that nutrient enrichment should be controlled to prevent excessive growth of cyanophytes, which form excessive blooms and thereby prevent growth of other algae such as diatoms, which were selected by fish in both habitats.

Keywords:

• algae
• Bacillariophyta
• Cyanophyta
• selectivity
• stomach content
• Shirati Bay