RECOVERY OF A WARMWATER FISH ASSEMBLAGE AFTER THE INITIATION OF A MINIMUM-FLOW RELEASE DOWNSTREAM FROM A HYDROELECTRIC DAM

Artificial fluctuations in streamflow caused by hydroelectric power da ms can degrade fish habitat and reduce the abundance and diversity of riverine fish faunas, Increased minimum water releases and reduced flu ctuations in discharge may mitigate these effects. In this study, we c ompared shoreline fish abundance and diversity before and after an enh anced flow regime was implemented on the Tallapoosa River (Alabama) do wnstream of a hydroelectric dam. Before the minimum-how regime, only e ight species of fish were collected 3 km downstream from the dam, and all were classified as macrohabitat generalists. After the minimum flo w was initiated, species richness 3 km below the dam more than doubled , and over half of the species collected were classified as fluvial sp ecialists. Fish community response to the enhanced flow was not as gre at at a site 37 km downstream from the dam, where species richness was similar between the two periods. However, more species classified as fluvial specialists were collected after the minimum flow regime than before enhanced flows at this site. Additionally, relative abundance o f species classified as fluvial specialists increased from less than 4 0% of fish collected before enhanced flows to over 80% after minimum f lows began. Our results suggest that the enhanced flow regime provided conditions supporting a relatively abundant and diverse fish assembla ge more reflective of a riverine system.