Effects of Reservoir Drawdowns and the Expansion of Hydrilla Coverage on Year-Class Strength of Largemouth Bass

We examined the effects of reservoir drawdowns and hydrilla Hydrilla verticillata coverage on year-class strength of Largemouth Bass Micropterus salmoides at Rodman Reservoir, Florida. Average catch-curve residuals obtained from multiple age samples illustrated that four of the six cohorts produced during drawdowns were strong, whereas the majority of cohorts produced when pool levels were at normal depths were average to weak. Linear regression of average catch-curve residuals and the net change in percent area covered (PAC) by hydrilla were positively related (R-2 = 0.75) to cohorts produced during drawdowns, whereas no relationship was found between hydrilla PAC and cohorts produced when water levels were at normal pool. The Largemouth Bass fishery at Rodman Reservoir could be managed for strong year-classes in predictive intervals (3-4 years) by the current drawdown magnitude, timing, and duration if hydrilla PAC is managed accordingly.