Consequences of stream impoundment on fish communities in a small North American drainage

We examined impoundment associated fish community changes in the Kinkaid Creek drainage of southern Illinois by comparing collections made in 1998 and 1999 with a pre-impoundment survey conducted in 1958. We also analyzed other historical pre- and post-impoundment collections made during the past 60 + years. A dramatic change in fish community structure occurred with the pre-impoundment community dominated by cyprinids and the post-impoundment community now dominated by centrarchids. In addition, a 50% increase in the number of fish species known from the Kinkaid Creek drainage has occurred, with 35% of all species known from Illinois now present in the drainage. This increase in species richness coincides with the extirpation of six native species. Possible explanations for the changes in the species assemblage and increased species richness include the introduction and dispersal of non-native fish species and habitat alteration. Finally, we contend that processes, such as habitat alteration, must be considered when analyzing the pattern of increased species richness caused by non-native species seen in North American drainages.