ST. PAUL — The Minnesota Department of Natural Resources says more boaters are beginning to understand the state’s invasive species laws, and as a result the rate of violations is going down.

Of the more than 168,000 boats inspected in 2015, 3 percent arrived at lakes carrying plants or invasive species. Meanwhile, 95 percent of boaters had pulled the drain plug as required — the highest rate since the DNR started tracking inspections two years ago.

But zebra mussels were found in several new lakes this summer. The DNR said at least 550 of Minnesota’s 11,000 lakes

have some kind of invasive species.

“As more lakes become infected the opportunities become higher,” said Ann Pierce, DNR section manager of ecological water resources. “We have to become more diligent.”

Minnesota trained 660 watercraft inspectors this summer to slow the spread of aquatic invasive species.

“Our long term program has resulted in people understanding why it’s important to follow what the laws are and that’s why the violation rates are going down now,” Pierce said.

Jeff Forester, executive director of the Minnesota Lakes and Rivers Advocates, said the DNR needs to do more inspections. He said he believes every boat ramp at “super-spreader” lakes like Minnetonka and Mille Lacs should be monitored and all highways leading into Minnesota should have decontamination stations.

“Boats coming into the state should be stopped and decontaminated,” Forester said.

Pierce said that plan is not feasible and would be too expensive.