Zebra Mussels

Since the discovery of zebra mussels in Fall 2018, BLIA has monitored the infestation. If the progression is like other Minnesota lakes, maximum population will be reached in 2024 or 2025. Partnering with MAISRC,  every spring of 2020 through 2023, BLIA volunteers placed ZM devices on docks around the lake to check on the ZM’s progress and see where they were thriving. The ZM devices are essentially stacked plates of solid material that sit in the water. Zebra mussels in the area of the device will attach themselves to the plates, allowing us to count the zebra mussels and thus, monitor the level of zebra mussel invasion in that part of the lake. As many as 250,000 ZM’s can be concentrated in one square meter.

And in 2022, again we partnered with MAISRC to develop “Got Zebra Mussels? Now What?”

The Zebra Mussel Threat to Minnesota Waters

Invasive species cause recreational, economic, and ecological damage – changing how residents and visitors use and enjoy Minnesota waters.

Zebra mussel impacts:

  • Encrust equipment, such as boat motors and hulls, which reduces performance and efficiency and is costly to clean and repair
  • Swimmers and pets can cut their feet on zebra mussels attached to rocks, docks, swim rafts and ladders
  • Create a costly problem for power plants, cities and residents when they clog water intakes
  • Filter tiny food particles out of the water, which can reduce available food for larval and other animals, and can increase aquatic plant growth as a result of increased water clarity
  • Attach to and kill native mussels


Zebra mussels are small animals with a striped, D-shaped shell composed of two hinged valves joined by a ligament. The shells are typically one-quarter inch to one and one-half inches long, depending on age, with alternating yellow and brownish colored stripes. Adults are typically fingernail-sized and attach to hard surfaces underwater.


A single zebra mussel can filter one quart of water per day while feeding primarily on algae. They live underwater, attached to natural and [human]made substrates such as rocks, wood, plants, native mussels, pipes, docks, boat lifts, swim rafts, moored watercraft, and other debris. A female can produce 100,000 to 500,000 eggs per year. Fertilized eggs develop into microscopic, free-living larvae, called “veligers,” that form shells. After two to three weeks, the veligers settle and attach to a firm surface using tiny fibers called byssal threads. Beds of zebra mussels can reach tens-of-thousands within a single square yard.

Origin and Spread

The zebra mussel is native to Eastern Europe and Western Russia. The species was unintentionally introduced into the United States’ Great Lakes through the discharge of contaminated cargo ship ballast water. They were first discovered in the Great Lakes in 1988 and were first confirmed in the Duluth-Superior Harbor in 1989. 

The zebra mussel (Dreissena polymorpha) is a prohibited invasive species, which means it is unlawful and a misdemeanor to possess, import, purchase, transport, or introduce this species except under a permit for disposal, control, research, or education.

Boats at public accesses found bearing invasives are required to be decontaminated. The county and DNR operate mobile decontamination stations at various locations from May to September.

Find a location of the mobile unit:

Call 218-824-1055
Text CWCDECON to 1-833-258-7509

What you can do

People spread zebra mussels primarily through the movement of water-related equipment. Mussels attach to boats, docks, swim rafts and boat lifts. They can also attach to aquatic plants. Adult mussels can survive out of water – less than five days in dry conditions, but up to 21 days in very wet conditions, like inside dock and lift pipes. Microscopic larvae – or veligers – can survive in water contained in bait buckets, live wells, bilge areas, ballast tanks, motors and other water-containing devices.

Whether or not a lake is listed as infested, Minnesota law requires water recreationists to:

  • Clean watercraft of all 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
  • Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body

In the United States and Canada, facility managers use pesticides to kill zebra mussels in closed systems, such as water-cooling systems of power plants. Many pesticides used in closed systems are not allowed for use in open water. In natural waters, such as lakes or rivers, attempts to control zebra mussels are uncommon and considered experimental.