PLYMOUTH, Minn. - A popular west metro lake that has been the subject of urban water quality studies has suffered a blow with the confirmed presence of zebra mussels.

The Minnesota Department of Natural Resources (DNR) announced the infestation on Medicine Lake Thursday. 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 for the season.

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 added. “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.”

DNR experts say Fall is an important time to check for the presence of zebra mussels, when docks and boat lifts are being removed at the end of the boating season. Lakeshore and boat owners are urged to look on 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.

State 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. Minnesota law also 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.

The DNR says some invasive species are small and difficult to see at the access. To remove or kill them, boat owners should:

  • 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.

More information on zebra mussels is available at the Minnesota DNR website.