Vilas Land and Water summer boat washes prevent the spread of aquatic invasives

During busy summer months in the North Woods, Vilas County Land and Water Department hosts a series of free boat washes at popular public landings to help prevent the spread of aquatic invasive species such as the spiny water flea.

With this year’s schedule wrapping up over Labor Day weekend, Vilas County Land and Water’s Cathy Higley and staffers who helped with the program gave a brief overview of how things went.

Grace Maurer, lake monitoring and protection technician, said that it was great getting to interact with the community and North Woods visitors to spread awareness about AIS, specifically spiny water flea, while operating the decontamination unit throughout the summer.

“It was awesome seeing people care and appreciate our efforts and wanting to do their part in AIS prevention,” Maurer said. “It would be even better if we had more of this and more decontamination participation and openness as our work correlates to lake health, but even just talking with people and reminding and informing them about AIS seemed to make a difference.”

She added that some people wished the unit was available more often, while others were hesitant about the whole topic and process. “Caring is crucial!” Maurer reminded.

Higley noted that full data has not been processed yet, but that she expects much of the decontamination information to be similar to last year’s numbers. The biggest difference was that last year, the department was able to put in 152 volunteer hours where they decontaminated a total of 39 boats, which had to be decreased to closer to 100 hours this year.

Target lakes included Big Muskellunge, Star, Plum and Trout lakes. Big Muskellunge Lake is located 3 to 12 miles away from the three Vilas lakes that are already known to contain the spiny water flea: Plum Lake, verified in 2019; Star Lake, verified in 2013; and Trout Lake, verified in 2014.

In Vilas County, spiny water fleas also were discovered in Stormy Lake near Conover in 2007, and Ike Walton Lake in 2015.

Spiny water flea infestations

The locations of these cleanings were selected due to their proximity to three Vilas County lakes that are known to have spiny water fleas in an effort to keep them out of the surrounding waterbodies. Other factors considered when choosing the locations included the ability for wash water to infiltrate vs. run off into surface waters, boater traffic rates, and space available at the launch area.

According to the Wisconsin DNR, spiny water fleas entered the Great Lakes in ship ballast water from Europe in the 1980s. Only about ¼- to ½-inch in length, individual water fleas may go unnoticed, however, the species tend to gather in masses on fishing lines and downrigger cables, so anglers may be the first to discover a new infestation.

Spiny water fleas are predators — they eat smaller zooplankton (planktonic animals), which puts them in direct competition with juvenile fish for food. Young fish have trouble eating these water fleas due to their long, spiny tails. They produce rapidly through parthenogenesis, commonly known as asexual reproduction, which means that no males are required and populations can explode in number, the DNR said.
Once these spiny water fleas are introduced into a waterbody there is no effective strategy to control the invasive species, which is why preventing their infestations is so important.

The boat decontamination program is operated in partnership with UW-Oshkosh to offer voluntary washes using hot pressure washing. In Vilas County, the program has been in place since 2018, although it was halted from 2022-23 in order to make it more financially sound. It returned in 2024.

For more information or to volunteer to be a part of the program, contact Cathy Higley at Vilas County Land and Water at 715-479-3738.