A total ecosystem compartment model of a reservoir cove is described, with emphasis on the fish submodel. Nominal (unperturbed) annual cycles of selected compartments are presented, and results from three perturbation experiments (thermal pollution, eutrophication, piscivore invasion) are summarized. The ability of fishes to influence structure and function of the entire ecosystem (model) is demonstrated, and the role of top trophic levels in controlling the design of ecological communities is discussed. The status and prospects of total ecosystem modeling as a tool for fisheries science are considered.