Effects of river flows on growth of redbreast sunfish Lepomis auritus (Centrarchidae) in Georgia rivers
Effects of river discharge on growth of redbreast sunfish Lepomis auritus were investigated in nine rivers in Georgia, U.S.A. Fish were aged and annular total length increments (LTinc) estimated from measurements from sectioned sagittal otoliths using the generalized regression model that held for the effects of decreasing LTinc from annual age (X): LTinc=bo−b1(X) ±bi(D), where bo, b1 and bi were the regression coefficients for the intercept and slopes and D, discharge, was either a single or multiple measurements of annular or seasonal flow volume or variation in flow volume. For eight of nine rivers, higher or greater variation in flows from April to June was associated with greater L. auritus growth; in the last river, higher flows from January to March were associated with greater fish growth. Across all rivers, L. auritus growth increments were 22, 45 and 36% greater in a wet year v. a dry year at ages 1, 2 and 3 years, respectively. Based on the results of this study, increasing water withdrawals by an additional 30% in five Georgia rivers would reduce the predicted number of L. auritus recruiting to 203 mm (angler preferred size) by 19–62%.