News release: Zebra mussels confirmed in Thunder Lake in Cass County

December 27, 2021

The Minnesota Department of Natural Resources has confirmed a report of zebra mussels in Thunder Lake, near Remer in Cass County.

A lake property owner contacted the DNR in late October after finding zebra mussels on a boat lift being removed from the water for the season. A subsequent DNR shoreline search did not reveal additional zebra mussels. Two DNR K9s trained to detect zebra mussels were brought in, with the cooperation of lake property owners, to search lake properties and equipment. K9s Storm and Brady, and their conservation officer handlers Hannah Mishler and Julie Siems, checked about 20 properties and 50 pieces of equipment. They found four zebra mussels attached to equipment adjacent to the site of the original report.

“Lake property owners and lake service provider businesses play an important role in detecting invasive species, by carefully examining boats, docks and lifts when they are being removed from the water at the end of the season,” said Heidi Wolf, DNR invasive species unit supervisor. “The initial report from a lake property owner and the cooperation of others were crucial in detecting zebra mussels in this lake.”

As a reminder, Minnesota law requires that docks and lifts remain out of the water for at least 21 days after removal from a waterbody before they can be placed into another waterbody. In addition, anyone who transports a dock or lift from a shoreline property to an off-site location for storage or repair may need a permit to help prevent the spread of aquatic invasive species.

There are important prevention considerations for lake property owners:

  • Look on the posts, wheels and underwater support bars of docks and lifts, as well as any parts of boats, pontoons and rafts that may have been submerged in water for an extended period.
  • Anyone paid to remove boats, docks, lifts and other water-related equipment must be DNR trained and permitted. A list of DNR-permitted lake service provider businesses is available on the DNR website.
  • Contact an area DNR aquatic invasive species specialist if an invasive species is discovered that has not already been confirmed in that waterbody.

More information is available at