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

Abstract

Artificial fluctuations in stream flow 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 generalises. 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.

Impoundment impact on populations of facultative riverine fish

“…There are some North American studies (Ney & Mauney 1981, Erman 1986, Koryak & Hoskin 1994, Travnichek et al 1995, but the facultative riverine species from that continent are taxonomically different from those in Europe, hence comparisons are difficult.…”

A Tale of Two Rivers: Implications of Water Management Practices for Mussel Biodiversity Outcomes During Droughts

“…Increasing minimum flows has been shown to increase the ecological integrity of benthic aquatic insect and fish communities (Connor and Pflug 2004;Bednarek and Hart 2005;Decker et al 2008;Bradford et al 2011), but these studies often restore flows with the purpose of rewetting previously dry reaches instead of increasing existing flows (but see Travnichek et al 1995). However, in a long-term study Maynard and Lane (2012) found that increased minimum flows led to an increase in macroinvertebrate diversity.…”

A Database and Meta-Analysis of Ecological Responses to Stream Flow in the South Atlantic Region

“…Downstream from these dams the magnitude of flow fluctuations is reduced and fish assemblages become more abundant and diverse and fluvial specialists can persist (Kinsolving and Bain 1993;Scheidegger and Bain 1995). After instituting minimum flows below hydroelectric dams, the species richness doubled, abundance of fluvial specialists increased (Travnichek et al 1995), and growth and condition increased (Weisburg and Burton 1993). After flow augmentation in a small creek in Pennsylvania, Normandeau Associates (1995) documented an increase in abundance of fish and benthic invertebrates, a decrease in incidence of black spot parasitism, and increases in growth rates of fishes.…”