Much additional information on causes of early mortality of game fish is necessary for effective fish management and establishment of water quality standards for protection of important fish species. Research has been directed primarily toward determining mechanisms responsible for first-year mortality of largemouth bass (Micropterus salmoids) and developing technology needed to quantify their significance. Specific studies have included: (1) research on methods of marking and sampling small fish to permit identification of individuals and estimates of population size and survival; (2) controlled laboratory studies on the effects of incubation temperature on the survival of largemouth bass embryos; (3) investigations of the food, feeding habits, and bioenergetics of bass larvae; (4) studies of the interacting effects of dissolved oxygen concentration and fanning on the survival of largemouth bass embryos; (5) evaluation of predation as a source of mortality of embryos and larval bass, and (6) research on development of a natural or artificial food source for larval bass in laboratory experiments. Results are summarized. Several publications and reports on this research, and on the related issue of the ecological consequences of nuclear power plants, are listed.