IngentaConnect Cascading effects of introduced Nile perch (Lates niloticus) on t...

Authors: Bwanika, G. N.¹; Chapman, L. J.; Kizito, Y.¹; Balirwa, J.²

Source: Ecology of Freshwater Fish, Volume 15, Number 4, December 2006 , pp. 470-481(12)

Abstract:

Bwanika GN, Chapman LJ, Kizito Y, Balirwa J. Cascading effects of introduced Nile perch (Lates niloticus) on the foraging ecology of Nile tilapia (Oreochromis niloticus).

Nile tilapia (Oreochromis niloticus L.) is the dominant of the introduced tilapiines in many East African lakes and has flourished in the presence of introduced Nile perch (Lates niloticus L.). We explored the hypothesis that O. niloticus exhibits increased omnivory in response to a decline in abundance of haplochromine cichlids. First, we quantified variation in habitat use and diet of O. niloticus in Lake Nabugabo, Uganda. Second, we compared the diet of O. niloticus in lakes with (Nabugabo, Victoria) and without (Mburo, Wamala, Nyamusingiri, Kyasanduka) introduced Nile perch. In Lake Nabugabo, a higher level of phytoplanktivory was observed in small juveniles than in larger fish and in wetland ecotone areas where haplochromines were most abundant. An omnivorous diet dominated by detritus and invertebrates was recorded for O. niloticus in lakes Nabugabo and Victoria, while a predominantly herbivorous diet was characteristic of O. niloticus in lakes without Nile perch. Availability of a broad food base in lakes where inshore insectivores have been reduced may explain the increased omnivory recorded in lakes Nabugabo and Victoria.

Keywords: non-indigenous species; Lake Victoria; East Africa; diet; habitat use; herbivory

Document Type: Research article

DOI: 10.1111/j.1600-0633.2006.00185.x

Affiliations: 1: Department of Zoology, Makerere University, Kampala, Uganda 2: Fisheries Resources Research Institute, Jinja, Uganda

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Cascading effects of introduced Nile perch (Lates niloticus) on the foraging ecology of Nile tilapia (Oreochromis niloticus)