Dynamics of the offshore fish assemblage in a southwestern reservoir (LakeTexoma, Oklahoma-Texas)

Reservoirs are relatively new ecosystems with fish assemblages that include both native and introduced species, Spatial and temporal variability in su ch fish assemblages is difficult to predict from ecological theory. We char acterized the dynamics of an offshore fish assemblage of Lake Texoma by sam pling multiple fixed sites fortnightly with gill nets from 1981 to 1984 (40 2 net-nights). Univariate and multi-variate analyses were used to quantify (1) variation of the fish assemblage in space and time, (2) spatial and tem poral independence of samples, (3) persistence of species associations, and (4) correlations between the dynamics of the fish assemblage and environme ntal conditions. Overall, depth and season accounted for the greatest amoun t of variation in the fish assemblage in our study area. Much of this varia tion was the result of spatial and temporal fluctuation in the abundance of various age classes of Dorosoma cepedianum (Gizzard Shad), Morone saxatili s (Striped Bass), and Aplodinotus grunniens (Freshwater Drum). With the exc eption of a winter kill of the nonnative Dorosoma petenense (Threadfin Shad ), the reservoir fish assemblage differed little among years. Species assoc iations were constant across years during the warm season but not in cold s easons, Overall, the fish assemblage in our study area remained relatively consistent, in spite of considerable variability in reservoir volume, turbi dity, and temperature.