Feeding ecology of the intensively fished Nile Perch, Lates niloticus, in Lake Victoria, Uganda

Abstract

The diet of Nile Perch (8.0–121.0 cm total length [TL]) from the Ugandan waters of Lake Victoria was quantified through stomach content analysis of specimens collected from experimental catches and fish factory samples. A total of 7824 stomachs (5602 from experimental fishing and 2222 from factory samples) were examined, of which 34.8% contained food. Fish from the experimental catches were smaller (8.0–41.6 cm TL) and had a higher diversity of prey dominated by unidentifiable fish prey, haplochromine cichlids, Rastrineobola argentea, Odonata and Caridina nilotica, while larger fish (30.0–121.0 cm TL) from the factory samples had a predominance of fish remains and haplochromine cichlids. Nile Perch that had a high proportion of fish prey (versus invertebrates) in their stomachs showed a larger size for a given age, and were in a better condition (K = 1.24) than those that had primarily invertebrates (K = 1.10) in their stomachs. Nile Perch exhibited a much smaller size (15 cm versus 30 cm TL) at shift to piscivory in comparison to Nile Perch examined in earlier studies, when haplochromines were rare in Lake Victoria. The recovery of haplochromine cichlids coincident with declining Nile Perch densities illustrates the importance of developing sustainable management options that can define a proper balance between fishing mortality and Nile Perch predation.

Keywords:

• Nile Perch diet
• haplochromine resurgence
• introduced species
• ontogenetic shift
• piscivory

Acknowledgements

Financial support to conduct this study was obtained from the Lake Victoria Fisheries Organization (LVFO) as part of a Ph.D Scholarship. We wish to thank the staff of the National Fisheries Resources Research Institute (NaFIRRI), and of the Department of Zoology, Makerere University, for support given during the course of this study.