From the MN DNR:
"The new northern pike fishing regulations, which were announced recently and go into effect on the May 12 fishing opener, have three distinct zones to address the different characteristics of pike populations in Minnesota, according to the Department of Natural Resources.
Each of the zones – north-central, northeast and south – provide protection for different sizes of pike, and there are reasons for those differences.
“We’re continuing to let anglers know there are new pike regulations for those who want to keep pike on inland waters,” said Chris Kavanaugh, DNR northeast region fisheries manager. “We also want to share the thinking behind the new regulations.”
The north-central zone is the largest of the three zones, and here the possession limit is 10 northern pike, but only two can be longer than 26 inches; and all from 22 to 26 inches must be released.
“We’re responding to angler concerns about the over-abundance of small, or hammer-handle, pike in the north-central zone,” Kavanaugh said.
Through anglers keeping small fish but protecting the 22 to 26 inch pike, the objective in the north-central zone is to both reduce the abundance of small pike and allow medium size pike to grow larger.
The advantages of growing larger pike are twofold. While protected these medium size pike will eat small pike, helping reduce abundance of small pike. And when they eventually grow out of the protected size range they will be a more desirable size for keeping."