Discovery of common carp in Nicollet County’s Swan Lake is prompting the Minnesota Department of Natural Resources to consider a temporary lowering of the lake’s water level.
Common carp can quickly degrade lake habitat and water quality through their feeding actions.
“It appears we’ve discovered the common carp population early,” said acting Nicollet area wildlife manager Stein Innvaer. “Fortunately, that provides us with time to thoroughly consider our management options before habitat and water quality are seriously impacted.”
There are few options available to control carp but lowering water levels is a proven management technique and has been done on Swan Lake before. Lowering lake levels could create conditions conducive to a winterkill. A partial draw down of water levels has already begun because of unusually high water levels the last two years. Current plans are to lower the lake level by one foot. However, the discovery of common carp could cause wildlife managers to lower the lake even more.
“Habitat and water quality on Swan Lake right now are good,” Innvaer said. “However, high water levels are killing off some important aquatic vegetation. Clear water and a high diversity of desirable vegetation are important features that make Swan Lake a premier waterfowl destination.”
At more than 10,000 acres, Swan Lake is widely considered North America’s largest prairie pothole lake. Swan Lake saw its last drawdown in 2005, an action that was successful in dealing with the carp population at that time. Drawdowns mimic droughts, which can act as a reset mechanism to allow native vegetation to re-establish and improve water clarity in shallow lakes and wetlands.
DNR wildlife managers plan to meet with the public to inform them about the problem with carp and possible solutions. A meeting date has not yet been set.
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