The Cichlid Fishes of Lake Malawi, Africa

Summary of Publication

Wanink, J.H., and F. Witte. 2000. The use of perturbation as a natural experiment: Effects of predator introduction on the community structure of zooplanktivorous fish in Lake Victoria. Pp. 553-570 in: Rossiter, A., and H. Kawanabe, eds. Ancient lakes: Biodiversity, ecology and evolution. Advances in Ecological Research, volume 31. Academic Press, London.  

This chapter illustrates the importance of ancient lakes as natural laboratories for the study of community structure. The major problem in this field, assessing the relative importance of competition and predation, can be success-fully attacked by the use of human perturbation as a natural experiment. Using East African Lake Victoria as an example, the effects are reviewed of eutrophication; overfishing and invasive aliens on several communities within this complex ecosystem. The long-term study by the authors' research team on the zooplanktivorous fish community of Lake Victoria provided the opportunity to use the explosive population increase of an introduced predator, the Nile perch Lates niloticus, as a natural experiment. Changes in population densities, habitat choice and life histories of the zooplanktivores suggest a shift from a community structured by competition to one structured by predation. Although the complexity of their foodwebs may complicate the separation of the structuring factors, it may be concluded that ancient lakes, which are almost inevitably exposed to human perturbation, offer unique opportunities to study community structure.




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