if he looks like this, its a black crappie. My "daughter" caught this little 4" one a few weeks ago.
I really don't understand Minnesota's "native" fish rules. Kids 0-16 years are allow to keep and transport up to 4 of each species UNDER 13" for home aquarium "educational" use but people 17+ are not. You can also get them from a pet store BUT you MUST have the receipt for the purchase.