The Minnesota Department of Natural Resources has confirmed a report of zebra mussels in the Embarrass Mine Pit, also known as the Sabin Mine Pit, near Aurora in St. Louis County. Mining in the Embarrass Mine Pit stopped in 1977.
A U.S. Forest Service employee contacted the DNR after finding several zebra mussels while swimming in a public area at the north end of the pit. A DNR invasive species specialist subsequently found adult zebra mussels in several locations in the 155-acre pit. Embarrass Mine Pit is stocked with stream trout and other fish species, making it popular with anglers. It has a maximum depth of 465 feet.
Zebra mussels were confirmed in the nearby St. James Mine Pit in Aurora in July 2021, after an initial report from the same individual to the DNR. The DNR is working with the city of Biwabik, which draws water from the Embarrass Mine Pit for municipal and domestic use.
Zebra mussels can cause expensive damage to water intake pipes and can reduce or block water flow into intake pipes. Water containing zebra mussel larvae, called 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 downstream receiving waters.
Whether or not a lake has any invasive species, Minnesota law requires people to:
Clean watercraft, trailers and equipment to remove aquatic plants and prohibited invasive species.
Drain all water and leave drain plugs out during transport.
Dispose of unwanted bait in the trash.
Never release bait, plants or aquarium pets into Minnesota waters.
Dry docks, lifts and rafts for 21 days before moving them from one water body to another.
These additional steps reduce the risk of spreading aquatic invasive species:
Decontaminate watercraft and equipment – find free stations on the courtesy decontamination page of the DNR website (mndnr.gov/Decon).
Spray with high-pressure water or rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds).
Dry watercraft and equipment for at least five days before using in another water body.
In addition to damaging water intake pipes, zebra mussels can compete with native species for food and habitat, cut the feet of swimmers and reduce the performance of boat motors.
People should contact a Minnesota DNR aquatic invasive species specialist (mndnr.gov/Invasives/AIS/Contacts.html) if they think they have found zebra mussels or any other invasive species.
More information is available on the aquatic invasive species page of the DNR website (mndnr.gov/AIS).