This first attachment shows 26 years of Wisconsin trout stamp sales data. Central office fish folks had the nerve to count every Patron Card buyer as one trout angler which is FRAUD. Only a small percentage of PC buyers are trout anglers. Plus TU folks buy multiple stamps to support the program.
In the 1980s Wisconsin had almost 200,000 trout anglers. The low point was 1991 when special regulations were implimented back in 1990. An the numbers have never come back since. I do not have data for Minnesota but do believe if I did it would show the same thing.
The second attachment is an example of the Big Green River showing trout numbers at ~100/mile back in the 1960s – 1980s and then jumping up to ~3000/mile+ in the 1990s – present. I could give you a ton of examples. If you have fished trout streams recently you might even think we have a problem.
Aside from record trout numbers and a big angler decline there have been other changes. Early on locals fished and they were primarily bait and spin anglers. Now fly anglers predominate. There have been several studies that show total trout harvest is now less than 10%.
In summary, the trout fishing in the Midwest is the best it has ever been. Tons of trout, nobody fishing, and those that are fishing are mainly fly anglers who practice catch and release.
Don’t be afraid to keep a few trout. There are some rivers that actually could use harvest — Upper Kinni, Coon Valley. High trout populations make them stunted.