The Minnesota Department of Natural Resources is holding mandatory invasive species training sessions around the state for lake service providers.
Employees of any business that moves boats, docks or irrigation equipment must have the training before the business receives a permit from the state.
About 800 businesses had workers trained last year, but many still don't have permits, said training coordinator April Rust.
Rust said the training will help slow the spread of invasive species like zebra mussels.
"We could really slow down the spread of a lot of species if everybody that's moving equipment between very different water bodies knows what to look for and how to decontaminate properly," she said. "Just a little bit of knowledge goes a long way."
Hundreds of workers still need the training, she added.
"The lake service providers attend a half-day training," Rust said. "They take a test, and once they pass that they can apply online for a permit and receive that in the mail. They are supposed to have a permit before they are working in the water."
More than 20 training sessions are being offered around the state this month and in March.
Businesses can be cited and fined if they move equipment into or out of a lake without a permit, Rust said. The minimum fine is $175.