MINNEAPOLIS — More boat inspectors are on patrol at Minnesota lakes and rivers to help stop the spread of invasive species, including zebra mussels, and authorities say they will be more aggressive about issuing fines to violators as they try to change boater behavior.

Counties are also beefing up inspections, thanks to $10 million in state funds.

Greg Salo, of the Department of Natural Resources’ enforcement division, said the state’s 148 conservation officers are out issuing tickets over the holiday weekend. He said 17 percent of boaters stopped at checkpoints disobey rules.

“The first few years we tried to focus on education; it’s kind of a culture change for people,” Salo said. “But we’ve gotten to the point now, to get the rest of the public to change, we have to take a stronger approach.”

More than 500 Minnesota rivers, lakes and wetlands are listed as infested, including more than 200 with zebra mussels, which can clarify water but also clog motors and hurt swimmers with their sharp shells.