Fact of life in fishing. State regs vary dramatically. But then so does the climate, which the various DNRs have to cope with to manage it. You don't have to come north either. There are lakes in Texas where the crappies also go deep enough in the winter that mortality is well over 90% on all releases, including those that don't look to be stressed and swim away. There you may not release any during particular times of the year, but must keep all and apply any caught to the prevailing limit. There seems to be a point somewhere in the twenty foot depths below where crappies brought up too quickly cannot tolerate the rapid change in depth and are mortally injured even if not visibly at the time.

A whole lot depends on the professional experience of local managers and they don't always agree with each other or with the politicians who fund them either.

The farther north one goes generally but not always the more stress our game fish are under, especially as one approaches the northern limits of their ranges. That process reverses where northern species approach the southern limits of their ranges. They have to be managed differently in different areas. It is up to us to adapt, I guess.