The Minnesota Department of Natural Resources has confirmed reports of zebra mussels in Hand Lake in Cass County and Upper Cormorant Lake in Becker County. Two smaller lakes and an unnamed wetland connected to Upper Cormorant Lake will also be listed for zebra mussels.

A Cass County watercraft inspector found a plant with attached zebra mussels on a boat coming from Hand Lake. Divers then found a 1-inch, adult zebra mussel in Hand Lake. The DNR is conducting further analyses to better determine the distribution of zebra mussels in the lake.

DNR divers conducted a search of Upper Cormorant Lake and found seven adult zebra mussels in four locations. Nelson Lake, Middle Cormorant Lake and an unnamed wetland connected to and downstream of Upper Cormorant Lake will also be listed for zebra mussels. The wetland flows into Big Cormorant Lake, where zebra mussels were confirmed in July of 2015.

Whether or not a lake is listed as infested, Minnesota law requires boaters and anglers to:

  • Clean watercraft and trailers of aquatic plants and prohibited invasive species.
  • Drain all water by removing drain plugs and keeping them out during transport.
  • Dispose of unwanted bait in the trash.

Some invasive species are small and difficult to see at the water access. To remove or kill them, take one or more of the following precautions before moving to another waterbody:     

  • Spray with high-pressure water.
  • Rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds).
  • Dry for at least five days.

Zebra mussels can compete with native species for food and habitat, cut the feet of swimmers, reduce the performance of boat motors, and cause expensive damage to water intake pipes.

People should contact an area DNR aquatic invasive species specialist if they think they have found zebra mussels or any other invasive species that has not already been confirmed in a lake.

More information is available at mndnr.gov/ais.