Recovery of a Warmwater Fish Assemblage after the Initiation of a Minimum-Flow Release Downstream from a Hydroelectric Dam

Abstract

Artificial fluctuations in streamflow caused by hydroelectric power dams can degrade fish habitat and reduce the abundance and diversity of riverine fish faunas. Increased minimum water releases and reduced fluctuations in discharge may mitigate these effects. In this study, we compared shoreline fish abundance and diversity before and after an enhanced flow regime was implemented on the Tallapoosa River (Alabama) downstream of a hydroelectric dam. Before the minimum-flow regime, only eight species of fish were collected 3 km downstream from the dam, and all were classified as macrohabitat generalists. After the minimum flow was initiated, species richness 3 km below the dam more than doubled, and over half of the species collected were classified as fluvial specialists. Fish community response to the enhanced flow was not as great 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 of species classified as fluvial specialists increased from less than 40% of fish collected before enhanced flows to over 80% after minimum flows began. Our results suggest that the enhanced flow regime provided conditions supporting a relatively abundant and diverse fish assemblage more reflective of a riverine system.