Ecomorphology of Fish Assemblages in an East-Central Illinois Stream

Habitat degradation has negatively impacted Midwestern stream fish assemblages. Understanding the complex dynamics within these systems can help mitigate losses. Our objective was to assess and model fish communities within a Midwestern stream influenced by anthropogenic pressures. We examined assemblages within seven reaches along Kickapoo Creek in East-Central Illinois. This creek is a region of decreased geomorphic stability and the site of multiple restoration projects. Fish communities were sampled in restored, reference, and impacted reaches using single-pass pulsed DC electrofishing. We describe community metrics for each reach and use principal component analyses to explain the factors driving species composition among reaches. Community assemblages within Kickapoo Creek are primarily influenced by factors relating to channel morphology and flow regime. Reaches with higher mean depths and larger pool areas displayed increased abundance of sunfishes while sites characterized by shallower depths and faster flows exhibited increased abundance of minnows and darter species. The variability between assemblage structures can be explained by habitat and ecomorphology of fishes. Evaluation of swimming mechanics in Kickapoo Creek fishes will help further explain the relationships between species distributions and flow dynamics.