Effectiveness of an Electrical Barrier and Lake Drawdown for Reducing Common Carp and Bigmouth Buffalo Abundances

Abstract

An overabundance of common carp Cvprinus carpio and bigmouth buffalo Ictiobus cyprinellus in North and South Heron lakes, Minnesota, has hindered production of food plants for waterfowl. These shallow (maximum depth, 1.5 m), turbid lakes are partially drawn down each winter. Common carp were radio-tracked in both lakes during the winters of' 1991 and 1992 to monitor their movements and survival. Four of six radio-tagged fish died during the first winter because of low water, but all of an additional 12 radio-tagged common carp survived the second winter. The fish overwintered in water 28–50 cm deep under about 40 cm of ice cover. To assess the ability of an electrical barrier across the outlet stream to prevent migration into the Heron lakes basin, 1,600 common carp and bigmouth buffalo were marked with dart tags and released downstream from the barrier. No tagged fish were among the 3,376 fish caught upstream from the barrier. Catches of the two species per unit gillnetting effort in South Heron Lake were lower in August 1992 than in August 1991, suggesting that lake-level drawdown and the electrical barrier reduced both populations.