Alterations in Lake Victoria's food chain connection and limnology have resulted following the introduction of Nile perch and Nile tilapia in the 1950s and '60s. This report presents analyses of samples drawn from the Lake and its fisheries between 1988-1990 and of feeding experiments conducted with several tilapia species in laboratories. An initial section contains an overview of fisheries since the 1920s and a general description of the limnological aspects of ecological modifications resulting from the introduction of Nile perch. A second section describes the fish communities in the Lake's drainage basin and fisheries. Tilapia feeding habits, as well as water chemistry and the stratification regime of the lake, are discussed in Section 3. Section 4 summarizes the physical measurements of temperature, conductivity, DO, and PH taken during 1990-91 and the beginning of 1992, and makes concluding remarks on stratification and biota. An extensive reference list is included. (Author abstract, modified)