Zebra mussels confirmed in Medicine Lake in Hennepin County

The Minnesota Department of Natural Resources has confirmed zebra mussels in Medicine Lake, northwest of Minneapolis in Hennepin County. 

A lakeshore property owner notified the DNR and Three Rivers Park District staff, when a lake service provider business found one adult zebra mussel on a dock they were removing from the lake. DNR invasive species staff confirmed two more adult zebra mussels attached to docks at separate locations, indicating a lake-wide presence.

“After at least six years of reports of zebra mussels on Medicine Lake that turned out to be negative, it’s disappointing to make this confirmation,” said DNR invasive species specialist Keegan Lund. “Most people have been highly vigilant in practicing ‘Clean, Drain, Dispose’ to keep zebra mussels and other aquatic invasive species out of this and other lakes.”

“The DNR has had several other reports on Minnesota lakes that turned out to be negative in just the past few weeks,” Lund said. “We appreciate the increased engagement of Minnesotans in not only keeping watercraft clean and drained, but also checking docks and boat lifts and letting us know if they see something suspicious.”

Fall is an important time to check for zebra mussels, when docks and boat lifts are being removed from lakes at the end of the season. Look on the posts, wheels and underwater support bars of docks and lifts, as well as any parts of watercraft or equipment that may have been submerged in water for an extended period.

Minnesota law requires that docks and lifts be allowed to dry for at least 21 days before being placed in another body of water, whether aquatic invasive species are present or not.

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

  • Clean watercraft 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, especially after leaving infested waters:

  • Spray with high-pressure water.
  • Rinse with very hot water (120 degrees Fahrenheit for at least two minutes or 140 degrees Fahrenheit 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.