The Minnesota Department of Natural Resources says over the years, efforts to slow the spread of zebra mussels and other invasive species have been effective. But each summer new challenges arise.

"We see bass and crappies and sunfish and northerns," said fisherman Mark Zachmann.

Mark Zachmann and his brother Jim know a good fishing spot when they see one. And for most of the summer, luck has been on their side.

"Any of these lakes in Minnesota, if you fish early this time of year, you can catch those kinds of fish," said Mark Zachmann.

But when the Zachmanns and others leave the lake, there may be more than just the fish they reeled in that are riding along.

"It's really important to remember that humans are the ones who spread aquatic, invasive species," said Christine Hokkala-Kuhns.

Hokkala-Kuhns is a regional watercraft inspection supervisor with the DNR. They've been proactive at public accesses across the state, such as Big Lake, setting up decontamination units that clean boats.

The DNR uses hot water - which up to 140 degrees - and high pressure to kill and remove any invasive species form the boat.

That includes zebra mussels but also an invasive algae called starry stonewort which has now been detected in 18 Minnesota lakes. Boaters who take part get a sticker to help spread the word about invasive species - including the fact that not everyone is familiar with the boat plug law.

"You want to make sure that all the plugs are removed from your watercraft, your bilge area. The live wells, the bait wells. And any other plugs you may have in your watercraft," said Hokkala-Kuhns.

The DNR hopes a little bit goes a long way.

"We really want everyone to remember that they are a part of the prevention and so the small steps they take now can help prevent a new infestation in the future," said Hokkala-Kuhns.

The DNR said about 8% of Minnesota lakes are infested with invasive species.

Algae like starry stonewort begins growing under the ice in the winter and can push out native plant species, hurting the fish population.