Boater access to two more Minnesota lakes is being tightened in hopes of preventing the spread of aquatic invasive species.

Seven Lakeview Township accesses on Lake Melissa and Lake Sallie south of Detroit Lakes have been closed for boat launching and removal, though they remain open for swimming and other uses.

The lakes aren't being closed to the public, however. Each lake has one state access that isn't affected by the closures, said Dave Knopf, township chairman. "It will make it a lot easier monitoring people coming and going from just one access,'' Knopf said. "Otherwise it would be impossible to monitor those two lakes.''

The Department of Natural Resources, lake association and community volunteers plan to inspect boats at the state accesses.

Zebra mussels have been found in nearby Pelican Lake, and Knopf said the township and Melissa-Sallie Lake Association is trying to prevent the infestation of those two lakes.

"We don't know it will succeed, but we want to at least try,'' said Mary Ann Bond, president of the association. "By having one access point on each lake, chances are greater of catching a boat with invasive species.''

Boulders were placed Thursday at the closed accesses.

Minneapolis park officials recently imposed new restrictions on boat traffic on city lakes, closing accesses when inspectors aren't present. And Shorewood now requires boats to be inspected before launching in Christmas Lake.