KIDD, Michael R.*; KOCHER, Thomas D.; University of New Hampshire; University of New Hampshire: Spatial and Temporal Dynamics of a Community of Translocated Cichlids around Thumbi West Island in Lake Malawi

The economic and ecological consequences of invasive species has prompted the need to identify intrinsic and extrinsic factors that affect the dispersal of nonindigenous species within a novel environment. During the 1960�s and 70�s, an ornamental fish exporter captured numerous cichlid species endemic to northern Lake Malawi and introduced them to the species rich rocky shoreline of Thumbi West Island within Lake Malawi National Park. The translocation of 17 closely related species provides the opportunity to evaluate the relative ability of species to disperse across a contiguous habitat. During the summer of 2001, 24 line transects were surveyed around Thumbi West Island. This census was compared to surveys performed in 1980 and 1983 in order to evaluate the stability of this community and identify factors effecting species dispersal. A quarter of a century after their initial introduction, the translocated cichlid community around Thumbi West Island is still in an extreme state of unrest. Many species continue to spread around the island and have begun to colonize the mainland coast. Several species that initially underwent a rapid range expansion have since collapsed. Even species that have maintained consistent ranges over time, demonstrate significant changes in the distribution of abundance within that range. The rate of dispersal appears to depend on trophic utilization, population density, trophic competition, and availability of suitable habitat. Specialized planktivores dispersed more rapidly than generalist and algivorous species. There is evidence that native Labidochromis vellicans is negatively impacted by competition with introduced algivorous Labidochromis spp..