Minnesota natural resources officials fight invasive species with laws, higher fines and more inspections. But that may not be enough.
A bit of psychology might help stop zebra mussels from moving from one of the most popular lakes in the state.
As he stands at a public boat launch, Rick Klocek, a marina owner on Lake Minnetonka, talks about what zebra mussels are doing to the lake.
"You go out to Big Island, it's just scary out there what is going on," Klocek said. "All the clams are full of the zebra mussel, every piece of stone or tree bark, plastic bags, weeds are full. It's really bad."
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Zebra mussels were first found in Lake Minnetonka two years ago. Since then, the mussels have spread quickly by hitching a ride on boats, vegetation and rocks. The mussels are crowding out native species and threatening the lake's water quality.
The zebra mussels are a stubborn nuisance, said Nate Beaver, watercraft inspector for the Department of Natural Resources.
"They will attach to any hard surface and also vegetation and rocks. People will cut their feet on them in the lake when they are walking on the rocks," Beaver said. "Any hard surface and vegetation, they'll attach to."
To stop the spread of invasive species, Minnesota law requires people to clean, drain and dry their boats before entering and leaving the water. But recent surveys by the state Department of Natural Resources and other groups find that one in five boaters are not complying with the law.
At Lake Minnetonka, Hennepin County is trying to grab boaters' attention. Bright lights draw attention to a new invasive species inspection station. Big signs instruct boaters to remove all vegetation and weeds, drain and dry their boats.
University of Minnesota research helped with the design of the county's new $40,000 inspection station. Hennepin County's Angie Timmons says that research found most boaters were aware of the problem of invasive species but were unsure what they should do about it. The new design addresses that problem, she said.
"Creating some physical space so that it's very easy and obvious to boaters to understand what they should do and where to do it and giving them those prompts to remind them specifically what they should do," Timmons said.
The university research also found there was social pressure at launches to move in and out of the water quickly to make way for other boaters. That kept boaters from taking the time to remove invasives.
The new program, which rolled out several weeks ago, is already working, Timmons said.
"People generally are following the instructions," she said. "They appreciate having the space and the cues to know where to go and how to do it and getting that reinforcing mesage that their actions do make a difference."
Controlling invasive species in Lake Minnetonka is critical because so many boaters go from Lake Minnetonka to other Twin Cities lakes.
"The number one place that people come from or go to next if they are using a Minneapolis lake other than another Minneapolis lake is Lake Minnetonka and that was very frightening to us," said Deb Pilger of the Minneapolis Park and Recreation Board.
"The possibility of us getting infested with zebra mussels increased dramatically. It just became a much more real threat to us because of people moving in and out," Pilger said.
Concern over the spread of zebra mussels from Lake Minnetonka led the city to step up its own invasive species enforcement, she said.
Beginning Friday, the city will cut the number of hours public boat launches are open at Lake Calhoun, Lake Harriet and Lake Nokomis. That's so inspectors can look over boats as they come and go during the most busy times.