ST. PAUL, Minn. (AP) - The Minnesota Department of Natural Resources says boaters are violating rules against aquatic invasive species at an unacceptable rate.

The agency said Monday that the violation rate is 20 percent so far this year. Maj. Phil Meier, the DNR Enforcement Division operations manager, says the majority of those violations could have been avoided.

As part of a stepped up efforts to combat aquatic invasive species like zebra mussels, the DNR began extra patrols May 12 that will continue through the summer.

Through June 6, conservation officers issued 193 criminal citations for invasive species violations, 463 civil citations, 975 written warnings and 267 verbal warnings for a total of 1,898.

Last year, the DNR issued about 850 citations or warnings, compared with 293 citations and warnings in 2010.