The Minnesota Department of Natural Resources (DNR) has confirmed the presence of zebra mussels in Lake Orono, near Elk River in Sherburne County. This is the first time zebra mussels have been confirmed in a Sherburne County lake.

The DNR also recently confirmed two other aquatic invasive species in Lake Orono: Eurasian watermilfoil and rusty crayfish. Lake Orono is an impounded portion of the Elk River.

The DNR received multiple reports of zebra mussels as the lake was drawn down earlier this month. Through a DNR permit, the city of Elk River drew down the lake level to prepare for sediment removal this winter to restore water depth. A DNR invasive species specialist found a reproducing population of zebra mussels at two locations, ranging in size from young of the year to adult.

While zebra mussels have not been eradicated from any lake after becoming established, early detection and heightened prevention efforts can help protect other bodies of water.

Whether or not any invasive species has been confirmed in a lake, 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 are an invasive species that 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.

Eurasian watermilfoil can form dense mats of vegetation and crowd out native aquatic plants, clog boat propellers, and make water recreation and navigation difficult.

Rusty crayfish are often aquarium pets that have been illegally released into the wild. Rusty crayfish can destroy aquatic plant beds, displace native crayfish species, breed with native crayfish to produce hybrid species, and compete with fish for food while also consuming fish eggs.

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

More information is available at mndnr.gov/ais.