I can give a small example of how limits improved one specific lake here in Ohio.
We have a small lake on state land that has been around for many years and the gill fishing was always just so-so. if you were really lucky you could catch a mess of gills, but anything over 8" was a real trophy, and if you got a 9" crappie then you hit the jackpot. Being northwest Ohio, and very few lakes to fish, this little lake got a ton of pressure in the summer.
About 10 or so years ago the DNR put a 10 fish limit for gills and crappie and ticked a lot of people off. In the past 4 or 5 years though, I have been able to ice fish and open water fish and usually can pick up a limit of gills in and hour or so on good days, sometimes I still have to sort through small gills. BUT now those ones I'm throwing back are bigger than the largest we used to catch. This year I have fished this lake at least 10 times on the ice, and I have only got my limit 3 times, but the gills are running 8'-9 1/4" consistantly and the very few crappie I have caught have been over 13". So this fishery has been greatly improved with limits in place.
Now, this lake is a smaller lake so I am not saying limits would have as much impact on some of the larger lakes, but I do think over time it would have to have some kind of impact.
I fish a lot of different lakes in Michigan and a few in Indiana and can typically find fish on any lake I go on, but I will sat that, on average, I do less size sorting in Michigan than I do in Indiana.
