I read an article in In-Fisherman that was discussing the decline of panfish numbers in Minnesota. Particularly, the decline of larger sized panfish. A contributor to the article was Dave Weitzel of the Minnesota DNR. He has been conducting research into why the decline is happening and how best to remedy the situation.

https://www.in-fisherman.com/editorial/managing-for-big-bluegills/382986
https://www.dnr.state.mn.us/fisheries/index.html