Assessing Effects of Impounded Water on Life History, Reproduction, and Diets of a Fluvial Specialist Fish

Abstract. Species richness and abundances of fluvial specialist fishes often decrease within waters impounded by dams, but mechanisms underlying these decreases are poorly understood. Purpose of this study was to assess the effects of impounded water on fluvial specialist Greenthroat Darter Etheostoma lepidum by quantifying differences in life history (i.e., age structure, life span), reproduction (i.e., gonadosomatic index [GSI], stages of ovarian development), and stomach contents (i.e., diet items and parasites) between a population taken from a lentic environment (Lake Site) and a lotic environment (River Site). Among fishes taken from both sites, Greenthroat Darters lived up to 1.5 y, spawned for 11 mo, and consumed primarily aquatic insects and crustaceans. Differences in reproduction were not detected between populations at the Lake Site and at the River Site. Greenthroat Darters taken from Lake Site consumed fewer diet items, fewer aquatic insects, and greater number of crustaceans than those taken from River Site; however, diet weight, percent stomach fullness, and percent empty stomachs were similar between sites. Greenthroat Darters taken from Lake Site exhibited lower condition factors than those taken from River Site, which corresponded with a greater number of parasites (i.e., Acanthocephala and Nematoda) in individuals taken from Lake Site. Differences quantified herein were not sufficient to cause extirpation of Greenthroat Darters in the impounded waters, given the species has persisted in the impounded water at least since the late 1800s; however, differences in diets and parasites might explain the lower abundance of Greenthroat Darters in Lake Site compared to River Site.