Zebra mussels detected at western Minnesota lake, raising Otter Tail concerns
Zebra mussels have turned up again near Otter Tail County, putting boats, docks and fishing gear on notice before they spread to more lakes. The DNR says cleaning and draining now matter more than ever.
A new zebra mussel detection at a western Minnesota lake is a direct warning for Otter Tail County’s own shoreline. With Ethel Lake and Lake Six already on the list, the next infestation could hit fishing access, resort traffic and the boat launches that keep local lakes busy all summer.
The Minnesota Department of Natural Resources says zebra mussels are a prohibited invasive species, and the agency has put about 9% of Minnesota’s 11,842 lakes on its infested waters list. By June 2025, the DNR had confirmed zebra mussels in 378 lakes and wetlands and had listed 292 more water bodies as infested because they are connected to waters where the species already exists.
Otter Tail County has already felt that spread. On July 14, 2025, the DNR confirmed zebra mussels in Ethel Lake near Ottertail after a staff member found them attached to native mussels. On Oct. 9, 2025, the agency confirmed zebra mussels in Lake Six near Frazee after reports from equipment being removed for the season. The same day, the DNR confirmed zebra mussels in Munson Lake near Detroit Lakes in Becker County after a boat lift was flagged there.
Those finds matter because the state’s rules are clear. Minnesota law requires people to clean watercraft and equipment, drain all water, dispose of unwanted bait and keep docks, lifts and rafts out of the water for 21 days before moving them between water bodies. The DNR says possession, transport, import or introduction of zebra mussels is unlawful except under permit.
The stakes reach far beyond nuisance clumps on a boat hull. Zebra mussels attach to hard surfaces, kill native mussels and clog water-supply infrastructure. University of Minnesota researchers say the species has altered aquatic food webs and caused economic damage tied to recreation, water treatment and hydroelectric uses. Their 2025 study said Minnesota became the state with the most zebra-mussel-infested lakes in the U.S. in 2024, underscoring how quickly the problem has spread.
For Otter Tail County lake users, the message is immediate: every dock pull, lift removal and trailered boat can either slow the spread or carry it into another lake. The DNR says anyone who thinks they have found zebra mussels or another invasive species not already known in a water body should contact a Minnesota DNR aquatic invasive species specialist.
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