Twenty-seven fish species were captured in Lake Oahe with trap nets in 1963-67. The catch was dominated by eight species in order of abundance: black crappie (Pomoxis nigromaculatus), bigmouth buffalo (Ictiobus cyprinellus), white crappie (Pomoxis annularis), carp (Cyprinus carpio), river carpsucker (Carpiodes carpio), freshwater drum (Aplodinotus grunniens), smallmouth buffalo (Ictiobus bubalus), and goldeye (Hiodon alosoides). Catch per unit of effort did not reflect changes in abundance of some of the species because of variation in environmental conditions. Frequency and strength of postimpoundment year classes were considered the best indicators of the ability of a species to adapt to reservoir conditions. Northern pike (Esox lucius), carp, smallmouth buffalo, and bigmouth buffalo established strong year classes in the early years of impoundment (1952-62), when previously unflooded terrain was inundated as the reservoir filled. The infrequency of abundant postimpoundment year classes and the limitations caused by spawning habitat requirements indicated that the abundance of these species will decline. Goldeye, channel catfish (Ictalurus punctatus), white bass (Morone chrysops), white crappie, black crappie, sauger (Stizostedion canadense), yellow perch (Perca flavescens), and freshwater drum which do not require inundated vegetation for spawning had better reproductive success after 1962 than before.