September 12, 2025–OTTER TAIL COUNTY, MN – Otter Tail County wants residents to know that the Minnesota Department of Natural Resources (DNR) has found zebra mussels and starry stonewort in Anna Lake near Underwood.
What is Starry Stonewort?
Starry stonewort is an invasive aquatic alga. It can form thick mats that make it hard to swim, fish, and boat. It also crowds out local plants that fish and wildlife need. You can spot it by its white star-shaped parts. These parts are easiest to see in late summer. Since 2015, starry stonewort has been found in 36 lakes and rivers in Minnesota. Starry stonewort has never been completely removed from any lake or river in the U.S. However, finding it early helps manage it better. Treatment can help reduce the spread. These harmful species spread when pieces are not cleaned off boats and equipment.
Prevention is Key
“We have watercraft inspectors at public accesses throughout the county, but we can’t be at every access all the time,” said Spencer McGrew, Otter Tail County Aquatic Invasive Species Specialist. “The public needs to do the right thing about clean, drain, and dry protocols every time they move between waterbodies.”
What the Law Says You Must Do
- Clean boats, trailers and equipment to remove water plants and harmful species
- Drain all water and leave drain plugs out when moving boats
- Throw away 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 to another lake
Extra Steps You Can Take:
- Clean boats and equipment at free stations (find locations at mndnr.gov/decon)
- Spray boats with high-pressure water or rinse if high-pressure water is not available
- Dry boats and equipment for at least five days before using them in another lake
Report Suspected Invasive Species
Call a Minnesota DNR water expert (mndnr.gov/invasives/ais/contacts.html) if you think you have found zebra mussels, starry stonewort, or any other harmful species in a lake where they haven’t been found before.
For more information about starry stonewort, please find the Otter Tail County Aquatic Invasive Species Handbook at ottertailcounty.gov/environment-natural-resources/invasive-species/