Minneapolis Parks and Recreation workers stood sentry at boat launches for 16 hours a day from April 28 through Nov. 30 last year, looking for zebra mussels and other aquatic invasives.

In those 3,472 hours, they found zebra mussels on one sailboat (twice) and possibly on two fishing boats at Lake Harriet.

But the monitoring was worth it, said Deb Pilger, director of environmental management for the parks district.

"If these species get into our lakes, whether it’s spiny water flea, hydrilla or zebra mussels, they’re impossible to remove," Pilger said. "And with zebra mussels, there are other costs associated with managing them."

The monitoring will take on a slightly different flavor once the ice melts off the lakes this year. In addition to checking boats entering and leaving the lakes (about 4,500 last year), the workers will also act as "public information ambassadors," offering information about concessions, trails and other amenities around city lakes, Pilger said.

The park board is expected to approve the changes for the upcoming season at its meeting Wednesday.

Pilger said the monitors may not start until May 1 or even later this year, given the expectation of a late ice-out this year (and the memory of a late one last year). Last year’s experience also means they’ll work reduced hours September through November, with November bringing an on-call system for inspectors. Boaters will find launches locked, but Pilger said the district will guarantee an inspector will show up within 15 minutes of being called to open the access.

Pilger said the plan emphasizes education over enforcement, and aims to have boaters picking up on the fine points of ridding their boats of zebra mussels and milfoil. (The aquatic plant hydrilla, which Pilger mentioned, isn’t in Minnesota yet.)