New Aquatic Invasive Found in Sturgeon Bay

A routine aquatic plant survey conducted for the City of Sturgeon Bay revealed the first presence of an invasive species new to Lake Michigan.

Starry stonewort, an invasive macroalgae, has been verified in the Sturgeon Bay Channel. It is the first confirmed discovery of the invasive plant in Lake Michigan and the first occurrence in the state outside of six southeastern Wisconsin lakes.

The population was discovered during the plant monitoring survey by a lake management contractor. The contractor provided photos and live specimens to the Wisconsin Department of Natural Resources and invasive species staff confirmed the finding through a verification process involving staff and independent experts from the New York Botanical Garden.

Bob Wakeman, DNR aquatic invasive species program coordinator, said the discovery reinforces the need for boaters to take action to stop aquatic invasive species. To prevent the spread of starry stonewort and other aquatic invasive species, Wisconsin law requires all boaters to:

  • Inspect boats, trailers and equipment including anchors and other places that accumulate sediment;
  • Remove all attached aquatic plants, animals and mud;
  • Drain all water from boats, vehicles and equipment; and
  • Never move plants or live fish away from a water body.

“Given Sturgeon Bay’s popularity as a destination for recreational boaters and anglers from across the region, starry stonewort has the potential to spread to many new lakes,” Wakeman said. “All boaters have the ability to stop the spread of invasive species by removing plants and draining water before leaving the boat landing.”

To help communities respond to this new threat and other aquatic invasive species, DNR can provide grants of up to $25,000 to start Clean Boats, Clean Waters watercraft inspection programs and fund management actions for recently discovered pioneer populations. Clean Boats, Clean Waters programs often use community volunteers to serve as watercraft inspectors at local boat launches. DNR also encourages citizens to become engaged in the Citizen Lake Monitoring Network, which provides access to training from lake experts from across the state.

Starry stonewort was first discovered in the U.S. in the St. Lawrence River in 1978 and has been documented in portions of the eastern Great Lakes as well as various inland lakes in Michigan, Indiana and Minnesota. It is becoming regarded as the most aggressive invasive species in inland lakes and has been recorded replacing other nonnative and nuisance species, including Eurasian watermilfoil.

It was discovered in Wisconsin 2014 and has negative effects similar to other invasive aquatic plants. By forming dense mats of vegetation, starry stonewort can reduce the diversity of aquatic plants in a lake. It can also impede movement of fish and other animals, and may impact spawning activity of some fishes. Mats growing to the surface can reduce water flow and make recreational activities difficult.

To learn more about starry stonewort, visit, and search for “regulated invasive algae.”

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