Seasonal Variations in Fish Assemblages of Small Warmwater Streams in Four Southeastern National Parks

Small warm-water streams in the southeastern United States experience significant differences in temperature, as well as changes in physical parameters due to seasonal fluctuations. It has been generally thought that fish assemblage patterns change as a direct result of these seasonal variations. This study was designed to determine the effects of variable flow regimes on fish species composition, diversity, and abundance. Eight small warm-water streams in four national parks (Chickamauga and Chattanooga National Military Park, Fort Donelson National Battlefield, Abraham Lincoln Birthplace National Historic Site, and Russell Cave National Monument) were sampled May-June 2005 for the summer trials, October-November 2005 for the fall trials, and April 2006 for the spring trials. All trials were conducted when water levels and flows were at normal seasonal stages. Fish populations were determined by electrofishing a 100-m reach at each site. Physical parameters including temperature, dissolved oxygen, conductivity, pH, and flow rate were also measured at each site. From summer to fall, the majority of the streams decreased in flow until temporary pools were formed. The lack of flow caused increased temperatures, decreased dissolved oxygen, and increased conductivity levels. As a direct result, overall fish abundance and diversity values decreased. From fall to spring, all the streams increased in flow, which brought back the riffle to pool habitat sequences. Dissolved oxygen levels increased, conductivity levels decreased, and temperatures became more stable. As a result, overall fish abundance and diversity values increased. Results indicated that fish assemblage patterns in the four parks did change as a direct result of the seasonal variations in habitat and water quality.