Aquatic invasive species prevention efforts show signs of success, DNR study says

MADISON. – There is good news in Wisconsin’s ongoing efforts against aquatic invasive species.

A new study by the Wisconsin Department of Natural Resources shows the spread of aquatic invasive species is stable, indicating prevention efforts may be working. A five-year search of 1,000 lakes — the largest effort of its kind in the country — revealed the rate of spread has not increased, but has remained stable.

Water lettuce
After an off-duty DNR employee discovered invasive water lettuce in Lake Mendota during the summer of 2015, a quick response by staff members as well as volunteers from the Clean Lakes Alliance, the UW-Madison’s Center for Limnology and the Hoofer Outing Club successfully eliminated the plant along the lake’s south shore.
Photo Credit: DNR

In addition, the survey showed that some of the most damaging aquatic invaders are being successfully kept out of the majority of Wisconsin lakes but that good news doesn’t mean we’ve stopped the spread. There is still a great deal of work everyone can do.

“While the stable invasion rate suggests our prevention efforts are having an impact, we would like to achieve an actual decline in the rate of spread,” said Bob Wakeman, DNR statewide aquatic invasive species program coordinator.Our next steps are to identity gaps in our education and outreach program to boaters and others who may unwittingly transport and introduce invasive species.”

This fall, Wakeman said DNR is making a special effort to reach out to waterfowl hunters. A few simple steps can help prevent decoys, boats, blinds and dogs from carrying aquatic invasive species from one hunting area to the next, Wakeman said. Before launching or leaving a water body:

  • Inspect waders, boats, trailers, motors and hunting equipment, including boots, blinds and dogs.
  • Remove all plants, animals and mud.
  • Drain all water from decoys, boats, motors, livewells and other hunting equipment.
  • Never move plants or live fish away from a water body.

The study project, funded largely by the federal Great Lakes Restoration Initiative, included efforts by a 150-member team of DNR staff, researchers, partners and volunteers that scoured lakes throughout the state for invaders such as Eurasian water milfoil, spiny water fleas, zebra mussels and purple loosestrife. Efforts focused on lakes with public boat access because boats are a primary pathway for invasive species to spread.

While the researchers discovered at least one undesirable species in nearly 75 percent of the lakes, it appears the most concerning invaders are being successfully kept out of the majority of lakes. For example, 90 percent of the lakes remained free of zebra mussels and 75 percent of lakes did not have Eurasian water milfoil.

“The study’s findings are important in a number of ways, including documenting conditions in lakes that have not been sampled before,” said Maureen Ferry, an aquatic invasive species monitoring coordinator for DNR and leader of the research effort. “Theoretically, invasion rates should increase over time because each new lake that hosts an invader can contribute to the spread. We found a constant rate, which suggests something – hopefully our outreach and education efforts – is preventing that acceleration from occurring.”

In recent years, those efforts have included campaigns such as Clean Boats, Clean Waters, which uses teams of volunteers as well as some paid staff from the DNR, Sea Grant and other organizations to help with boat and trailer checks to prevent the spread of aquatic invasive species. DNR also provides a variety of support to lake groups and communities to implement best practices and participate in monitoring and research efforts such as the five year study.

The research also showed that few of the newly detected species were actually new to the lake they had invaded; most had been lurking for some time in lakes that had never been monitored. The finding is important because early detection can lead to improved control with reduced economic impacts over time.

“Detecting invasive species early in establishment leads to much better control over time. So it’s really important for citizens to help monitor and report early populations,” Wakeman said.

In the months ahead, DNR also will continue its work to stop the spread of aquatic invasive species such as water lettuce and water hyacinth that may escape from water gardens, said Wakeman. For more information on Wisconsin’s invasive species rule and what hunters, anglers, boaters and other outdoor enthusiasts can do to prevent the spread of aquatic invasive species, search the DNR website,, for “Aquatic Invasive Species.”