As more and more people hit the water for fishing and recreation, it's also that time of year to be aware of where zebra mussels are and how to prevent spreading them.

An aluminum can encrusted with zebra mussels found at Crooked Lake in Lake County has resulted in the lake being designated as infested, according to the Minnesota Department of Natural Resources. Crooked Lake is located near the town of Finland. 

The initial discovery was reported by biologists from the Fond du Lac Band of Chippewa who retrieved the can while performing fisheries assessments at the lake. Following the positive identification of zebra mussels, a coordinated effort was established involving staff from DNR Fisheries, DNR Ecological and Water Resources, the Fond du Lac Band and the U.S. Forest Service to manage the lake as an infested water body.

Initial searches of the lake employing underwater cameras, sediment samples, plant rakes, down-imaging sonar and walking surveys were not successful in locating additional zebra mussels in the portion of the lake searched. Additional searches of Crooked Lake and connected downstream waters will be performed to determine the scope of the infestation.

“Although we weren’t able to locate additional adult zebra mussels on the first survey, designating the lake now as an infested water body is the right thing to do,” said Rich Rezanka, DNR invasive species specialist. “Lake users should follow the AIS protocols every time, at every lake, as if it were infested – whether signs are posted, or not.”

Crooked Lake is now designated as infested waters and signs will be posted at public accesses to alert recreationists.

Connected downstream waters to be investigated for infestation include:

  • Artlip Lake.
  • Houghtailing Creek.
  • Wanless Creek.
  • Cross River.

Recreationists should look for infested waters signage at public accesses. Signage will allow boaters and other resource partners to be aware of the finding and take additional precautions to prevent the inadvertent spread to other lakes. Bait harvest and transport of water for any purpose is prohibited in infested waters.

Before leaving any water access or shoreland, anglers, boaters and other recreationists are reminded to remove all aquatic vegetation, drain all water by removing drain plugs, and keep drain plugs out while transporting watercraft.

More information about zebra mussels, how to inspect boats and other water-related equipment, and a current list of designated infested waters is available on the DNR website at

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