CRB: Faunal Attenuation: Predicting Spatial and Temporal Dynamics of Refugia in the Lake Victoria Basin

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The introduction of exotic species into new habitats has negative effects on native species including predation on native species by introduced predators. In Lake Victoria, Uganda, Africa an estimated 50% of the 400+ native species of fishes have apparently disappeared in the last 15 years. One possible cause is predation by the introduced Nile perch, Lates niloticus. Previous studies have identified wetlands as important refuges protecting some fishes from Nile perch predation. These refugia may have low oxygen levels and structural complexity that protects adapted fishes by inhibiting perch dispersal into the wetlands. The objectives of this proposal are to 1) develop a predictive model of fish species richness and diversity for lagoon refugia; 2) examine the changes of fish communities in lagoons through field sampling and paleolimnological techniques; 3) apply predictions derived from small lagoon refugia to larger satellite lakes; and 4) examine how physical structure and oxygen concentration of wetlands affects lagoon colonization by Nile perch and prey species. The identification and protection of refugia has become critical to the survival of native fauna. This study will help identify characteristics of refugia that harbor remnant populations and that limit or permit use of refugia. The problems in the Lake Victoria Basin addressed by the principal investigators are relevant to the conservation of fishes in many wetland regions and have broader implications for the conservation of faunal remnants in many systems where taxa survive in small isolated patches.