Effects of Electroshock on Bluegill Feeding and Susceptibility to Predation

Abstract Electrofishing is a common technique used for the collection of freshwater fish. Although acute effects on fish (e.g., injury and mortality) have been examined, indirect behavioral effects (e.g., feeding and susceptibility to predation) have been relatively ignored. In the laboratory, we examined the effects of electroshock on food consumption by two size-classes of bluegills Lepomis macrochirus and on vulnerability to predation for one size-class. In aquaria, juvenile bluegills (47–55 mm) showed reduced feeding for up to 3 h postshock and no effects thereafter; adults (143–157 mm) exhibited reduced feeding for up to 12 h postshock. In 2.5-m-diameter pools, electroshocked bluegills were more vulnerable than control fish to predation by largemouth bass Micropterus salmoides when a predator was introduced immediately after electroshock, but vulnerability did not differ when the predator was introduced at 10 min postshock. We conclude that electrofishing inhibits feeding and increases vulnerability to predation but only for a short time. For bluegill populations, electrofishing can be an effective sampling technique for research and management with minimal negative consequences.