Hydro-peaking Impacts on Growth, Movement, Habitat Use and the Stress Response on Alabama Bass and Redeye Bass, in a Regulated Portion of the Tallapoosa River, Alabama

Abstract

Altered flow regimes caused by dam construction and operation can affect aquatic organisms in a variety of ways. The Tallapoosa River, in east-central Alabama, has been extensively impounded for flood control, navigation in the Alabama River, hydropower and water supply. None the less, the river still supports an important sport fishery. There has been previous research on the Tallapoosa River studying fish community responses to the altered flow regime. However, there has been minimal work on sportfish, including the black bass found within the river system. The objective of this research was to investigate the impacts of the altered flow regime on growth, movement, habitat use and the stress response on Alabama Bass Micropterus henshalli and Redeye Bass Micropterus coosae. Dams and altered flow regimes may impact growth of aquatic organisms. Using incremental growth techniques, annual growth of Alabama Bass and Redeye Bass in the Tallapoosa River was evaluated in response to variation in flow regime. Age was the best explanatory variable that described growth in all models, although flow variables were included in more than half the models. Growth was higher for age-1 fish in years with less flow variation; however growth was similar among years for age-2 and age-3 fish. Overall growth rates for Alabama Bass and Redeye Bass were higher in the unregulated sites, than either regulated sites. Alabama Bass had higher growth rates than Redeye Bass at the Middle and Lower sites; however growth was similar between species the upper site. From this study it appeared that growth was not severely impacted by the altered flow regime. Little is known about the movement and habitat use of Alabama Bass and Redeye Bass in the Tallapoosa River, specifically below R.L. Harris Dam, which operates as a hydropeaking facility. With the use of radio telemetry both species were tracked over 37 weeks to better understands movement and habitat use of these two species. Movement was strongly associated to season, with both species having the highest movement in the spring. No major difference was observed in movement based on the altered flow regime. However, shifts in habitat use were observed during the altered flows, which may be due to fish relocating to more suitable habitat or for better foraging. Lastly, stressors, such as alteration in temperature, oxygen or hydrology, can induce acute or chronic stress, which in turn can impact the overall fitness of an organism. Cortisol response is a good indicator of acute stress and additional measurements of stress include leukocyte profiles, with neutrophils increasing and lymphocytes decreasing (N:L). The physiological stress response was studied in both Alabama Bass and Redeye Bass, to determine if the altered flow regime has any impact. Results showed that there is a trend for both baseline cortisol levels and N:L to be higher in the fish found at the disturbed location. Additionally, the percent change of cortisol was higher at the reference site. Results suggest that fish in the treatment site have an altered stress response that may be due to the non-natural flow regime.