Field and Laboratory Evaluation of Dam Escapement of Muskellunge

Muskellunge Esox masquinongy occur in many Midwestern reservoirs where dam escapement is often reported. Because densities of Muskellunge in many reservoirs are low, escapement is a concern. Little is known regarding the factors that influence rates of Muskellunge dam escapement or the proportion of reservoir populations that escape annually. We used controlled laboratory experiments to examine how juvenile Muskellunge interact with flow over a barrier at varying levels of turbidity, flow rate, habitat availability, and periods in the diel cycle. In the field we inserted PIT tags into juvenile and adult Muskellunge, monitored their escapement over a dam with an antenna array, and then compared escapement among demographic groups and described escapement in relation to precipitation events, water temperature, and water clarity. Both laboratory and field studies found Muskellunge were more likely to escape during the day than at night. We estimated that 25% of a reservoir Muskellunge population escaped within the 1-year period of this study, with escapement occurring during late spring but not during fall. Adults were more likely to escape than juveniles, and both sexes escaped at equal rates. Methods developed here can be used to provide useful information to managers and develop mitigation practices to limit escapement in situations where it is not desirable.