Effects of natural flow variability over seven years on the occurrence of shoal-dependent fishes in the Etowah River
Hagler, Megan M.
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Annual fish surveys at ten shoals on the Etowah River, Georgia were conducted to assess the probability of occurrence of adult and young-of-year fish species under natural flow conditions over seven years, 1998-2004. Hierarchical logistic regression was used to simultaneously model factors thought to influence the occurrence of ten species from three families, Cyprinidae, Ictaluridae, and Percidae, including three imperiled species, at the microhabitat, survey, year and site levels. Microhabitat features were the strongest predictors of species occurrence. Increasing variability in summer stream flow (the number of days that stream flow exceeded the long-term average plus one standard deviation) reduced the odds of occurrence of most species. These findings suggest the need for stable summer flows in warmwater rivers to allow for strong species recruitment, with implications for the management of regulated rivers and possible response of natives fishes to climate change predictions for the southeastern United States.