The diet of Nile perch, Lates niloticus (L.) after resurgence of haplochromine cichlids in the Mwanza Gulf of Lake Victoria

Hydrobiologia (2012) 682:111119 DOI 10.1007/s10750-011-0822-1

SPECIATION IN ANCIENT LAKES

The diet of Nile perch, Lates niloticus (L.) after resurgence of haplochromine cichlids in the Mwanza Gulf of Lake Victoria

Mary A. Kishe-Machumu Frans Witte

Jan H. Wanink Egid F. B. Katunzi

Received: 7 November 2010 / Accepted: 15 July 2011 / Published online: 23 August 2011 The Author(s) 2011. This article is published with open access at Springerlink.com

Abstract Haplochromine cichlids used to be the main prey of the introduced Nile perch, Lates niloticus, in Lake Victoria. After depletion of the haplochromine stocks at the end of the 1980s, Nile perch shifted to the shrimp Caridina nilotica and to a lesser degree to its own young and the cyprinid Rastrineobola argentea. In the present study, we investigated the Nile perch diet in the northern Mwanza Gulf after resurgence of some of the haplochromine species and compared it with data collected in the same area in 1988/1989. It became clear that haplochromines are again the major prey of Nile perch. The dietary shift from invertebrate

feeding (shrimps) to feeding on sh (haplochromine cichlids) occurs at a smaller size than it did when Nile perch were taking primarily dagaa and juvenile Nile perch as their sh prey. The apparent preference for haplochromines as prey has reduced the degree of cannibalism considerably, which may have a positive impact on Nile perch recruitment.

Keywords Dietary shift Cannibalism

Caridina nilotica Haplochromines

Juvenile Nile perch Rastrineobola argentea

Introduction

Nile perch, Lates niloticus (L.), was introduced into Lake Victoria in the 1950s and early 1960s from lakes Turkana (Kenya) and Albert (Uganda) where it is native (Pringle, 2005). A dramatic increase of the Nile perch in the 1980s (Ogutu-Ohwayo, 1990a; Goudswaard et al., 2008) coincided with the disappearance of about 40% of the 500? endemic haplochromine cichlid species (Witte et al., 1992). Concomitant with the disappearance of haplochro-mine species, increases of the cyprinid Rastrineobola argentea (Pellegrin), locally called dagaa, and of the shrimp Caridina nilotica (Roux) were noted (Wanink, 1999; Goudswaard et al., 2006). About a decade later Nile perch yields declined due to intense shing, and resurgence of some haplochromine

Guest editors: C. Sturmbauer, C. Albrecht, S. Trajanovski & T. Wilke / Evolution and Biodiversity in Ancient Lakes

M. A. Kishe-Machumu...