Reservoirs are relatively new ecosystems with fish assemblages that include both native and introduced species. Spatial and temporal variability in such fish assemblages is difficult to predict from ecological theory. We characterized the dynamics of an offshore fish assemblage of Lake Texoma by sampling multiple fixed sites fortnightly with gill nets from 1981 to 1984 (402 net-nights). Univariate and multivariate analyses were used to quantify (1) variation of the fish assemblage in space and time, (2) spatial and temporal independence of samples, (3) persistence of species associations, and (4) correlations between the dynamics of the fish assemblage and environmental conditions. Overall, depth and season accounted for the greatest amount of variation in the fish assemblage in our study area. Much of this variation was the result of spatial and temporal fluctuation in the abundance of various age classes of Dorosoma cepedianum (Gizzard Shad), Morone saxatilis (Striped Bass), and Aplodinotus grunniens (Freshwater Drum). With the exception of a winter kill of the nonnative Dorosoma petenense (Threadfin Shad), the reservoir fish assemblage differed little among years. Species associations were constant across years during the warm season but not in cold seasons. Overall, the fish assemblage in our study area remained relatively consistent, in spite of considerable variability in reservoir volume, turbidity, and temperature.