Preliminary results from systematic monitoring of Wisconsin lakes for aquatic invasive species confirm that boaters, not ducks or other birds, are spreading the invaders around, state and University of Wisconsin-Madison researchers say.
None of the wilderness lakes surveyed – those in remote places and easily accessible only to wildlife – had any invasive species present while there was a direct link between the presence of invasive species and boat access from public and private property.
Thirty percent of the lakes with boat access, however, had Eurasian water-milfoil, 18 percent of the suitable lakes surveyed with boat access had zebra mussels, and three lake systems with boat access had spiny water fleas.
“The fact that accessible lakes are the ones that are invaded indicates that these species are moved by boaters,” says Alex Latzka, a University of Wisconsin-Madison graduate student involved in the research. “While birds could transport invasive species from one lake to another, our finding that remote lakes do not have invasive species strongly indicates that birds are not an important factor.”
In recent years, DNR and the UW-Madison have collectively surveyed 450 lakes for aquatic invasive species like zebra mussels, Eurasian water-milfoil and spiny water fleas.
UW-Madison researchers looked for aquatic invasive species in a range of lakes, including wilderness lakes.
DNR focused its sampling on those lakes more likely to have invasive species present because they had boat access that ranged from wide, paved public boat launches to private boat launches to yard access. DNR is two years into its 5-year sampling effort to understand the prevalence of aquatic invasive species in lakes statewide and also to understand whether efforts to slow the spread are working.
Two years of sampling is not enough to tell if the rate of spread is slowing in lakes with boat access, although there are some positive signs, says Scott Van Egeren, the DNR limnologist who coordinated DNR’s sampling over the past two years.
The number of lakes DNR surveyed and found with the different invasive species was about the same for both years. Finishing up the five years of monitoring will help provide information on the rate of the spread.
Most lakes with boat access were still free of the worst invasive species; 70 percent of the lakes with public access surveyed were free of Eurasian water-milfoil, despite the fact the invasive plant has been present in Wisconsin for more than 50 years and is considered a relatively widespread aquatic invasive species. And 82 percent of suitable lakes with public access are still clear of zebra mussels, present inland for more than 20 years.
“While we did find one or more invasive species in many of the lakes with private and public boat access, the prevalence of any one of them is relatively low given that some of these invasive species have been present in Wisconsin waters for decades,” Van Egeren says.
Bob Wakeman, who coordinates DNR response to aquatic invasive species, says the preliminary results underscore how important it is that boaters take the required steps to prevent the spread of aquatic invasive species.
Regulations since 2006 for oceangoing ships have effectively halted the introduction to the Great Lakes of new invasive species, Wakeman says, “so it’s up to boaters to keep those invasive species already in the Great Lakes from being spread to inland lakes.
“Out of 184 invasive species introduced to Lake Michigan over the past century, just 29 have made it to inland Wisconsin lakes,” Wakeman says. “Boaters have done a good job in recent years in following the rules, and they can continue to keep the damaging species out of inland waters as long as they take a few minutes to take some simple steps. “And we’re happy to say that ducks are not going to undo your hard work!”