Smith Mountain Lake, an 8,300 ha hydroelectric impoundment in south-central Virginia, experienced a sharp decline in its sport fishery beginning in the late 1970s. Potential causes were investigated over a three-year period and included: (1) increased hydroelectric pumpback operations; (2) reduced nutrient loading; and (3) trophic interactions between native and introduced fishes. Expanded hydroelectric operations did not substantially affect littoral and pelagic fish habitat. However, fish standing stock was highly correlated with total phosphorus concentration; both declined by over 75 percent between 1975 and 1984. Predation and competition of introduced and native fishes were minimized by habitat segregation, but forage fish production was inadequate to sustain a high abundance of piscivorous sport fishes. Restorative measures should focus on reduced piscivore stocking, increased harvest of juvenile sport fish, habitat enhancement, and adjustment of angler expectations to match the limits on fishery productivity imposed by other uses of the reservoir. This case study illustrates the need for effective planning in the management of reservoir fisheries, including consideration of issues at the design stage, frequent assessment, establishment of a protocol for introduction, new species, and compromise among users with different goals.