FISH ASSEMBLAGE STRUCTURE FROM 20 YEARS OF COLLECTIONS IN THE KIAMICHI RIVER, OKLAHOMA

We tested for long-term changes in fish assemblages using collections made from 1972 to 1992 in the Kiamichi River, Oklahoma. Reservoirs wer e constructed in the Kiamichi River basin in 1974 (mainstem) and 1983 (tributary). A significant difference was found for local species rich ness but not Shannon-Wiener diversity nor evenness in comparisons from before and after reservoir construction. There was an effect of colle ction date on the relationship between species richness and upstream d istance from the mainstem reservoir; species richness was highest prio r to reservoir construction. Sites further from the tributary reservoi r outflow were more similar in species composition over time than site s closer to the outflow. Comparisons of site scores for principal comp onents revealed that Fundulus olivaceus, Notropis atherinoides, and La bidesthes sicculus decreased in abundance following reservoir construc tion. Although the Kiamichi River retains its overall species richness , our results indicate that reservoir construction has influenced fish assemblage structure.