Zebra mussels confirmed in Grants Lake in Douglas County, West McDonald Lake in Otter Tail County


The Minnesota Department of Natural Resources has confirmed zebra mussels in Grants Lake in Douglas County and West McDonald Lake in Otter Tail County. 

During a treatment operation for a recently confirmed small population of the invasive plant flowering rush in Grants Lake, specialists from Douglas County and the DNR found multiple zebra mussels on a settlement sampler hanging on a dock. Settlement samplers are solid surfaces placed in the water that people can regularly check for attached zebra mussels.

zebra musselFollowing a credible report of a single adult zebra mussel in West McDonald Lake last month, DNR divers searched three areas of the lake. They examined more than 2,000 objects in the lake and did not find zebra mussels. During a follow-up search, DNR divers found two zebra mussels about 700 feet from the location of the original report.

Whether or not any invasive species has been confirmed in a lake or river, 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 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.

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

More information is available at mndnr.gov/ais.