The Minnesota Department of Natural Resources has confirmed zebra mussels in Cedar Lake, near the city of Aitkin in Aitkin County, and in the St. James Mine Pit, in Aurora in St. Louis County.

DNR invasive species specialists followed up on a report from a Cedar Lake user who found and photographed one adult zebra mussel in a swimming area. Three additional adult zebra mussels were found in the same area.

A U.S. Forest Service intern contacted the DNR after finding adult zebra mussels while swimming in the St. James Mine Pit. DNR invasive species specialists found more adult zebra mussels, and water samples taken from the mine pit had hundreds of microscopic zebra mussel larvae, called veligers.

Zebra mussels can cause expensive damage to water intake pipes and can reduce or block water flow into intake pipes. Water containing zebra mussel veligers must be filtered and/or treated to eliminate veligers before it can be used for drinking water or discharged, to prevent the spread of invasive species in the downstream receiving waters..

The DNR will be working with the city of Aurora and the Town of White on a contingency plan to address the rising water in the pit.

“It’s helpful when lake users contact us if they find what might be an invasive species that’s new to a lake,” said Heidi Wolf, DNR invasive species unit supervisor. “Early detection is important, because it can help prevent spread to other lakes.”

Whether or not a lake has any invasive species, 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.

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

More information is available at mndnr.gov/ais.