News Release

Zebra mussels confirmed in Swan Lake in Otter Tail County

October 21, 2019


The Minnesota Department of Natural Resources has confirmed individual zebra mussels in Swan Lake in Otter Tail County. Mineral Lake and several small, unnamed lakes connected to and downstream of Swan Lake will also be listed for zebra mussels. All of these lakes flow into North Ten Mile Lake, which was listed for zebra mussels in 2017. 

DNR invasive species specialists have conducted several searches of Swan Lake since a lake property owner brought in a dead adult zebra mussel her daughters found while swimming in the lake in July. No additional zebra mussels were found during subsequent dive searches in seven areas of the lake. At that time, specialists searched more than 3,700 objects and gathered water samples in seven areas of Swan Lake. The DNR conducted a further equipment search Oct. 9 and found one live juvenile zebra mussel about 200 yards from the location of the July report.

“It’s especially helpful when lake users contact the DNR after finding something suspicious,” said DNR invasive species specialist Mark Ranweiler. “Early detection of a small population allows us to remove any visible zebra mussels and to monitor a lake for potential spread.”

Lake property owners should carefully check boats and trailers, docks and lifts, and all other water-related equipment for invasive species when removing equipment for seasonal storage.

It is especially important to follow Minnesota’s law and keep docks and boat lifts out of the water for at least 21 days before putting them into another body of water. This state law is central to the training DNR-permitted lake service provider businesses receive.

Anyone transporting a dock or lift from a shoreline property to another location for storage or repair may need a permit, to help prevent the spread of aquatic invasive species.

The DNR recommends these steps 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.
  • Hire DNR-permitted lake service provider businesses to install or remove boats, docks, lifts and other water-related equipment. These businesses have attended training on Minnesota’s aquatic invasive species laws and many have experience identifying and removing invasive species.

People should contact an area DNR aquatic invasive species specialist if they think they have found zebra mussels or any other invasive species.

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, and 
  • 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.

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.

More information is available at mndnr.gov/ais.