Once again, you're looking for simplistic answers to complicated issues. Crappie populations are affected by many different factors.
#1: Minimum size limits on crappie are not the answer for every body of water. There have been cases where minimum size limits had no effect on average size, or actually made crappie fishing worse due to a large number of fish not reaching harvestable size.
http://www.tn.gov/twra/fish/Reservoir/Re...appie.html
http://files.dnr.state.mn.us/publication...ts/552.pdf
http://pubstorage.sdstate.edu/wfs/337-F.pdf
#2: Since when does "every boat there kill every crappie over 6 inches"? Do some people keep crappie smaller than they should? Probably. But most of the people I've seen there realize there's not enough meat on a crappie under 10" to be worth the effort to clean them and throw them back.
#3: You act like every boat is a panfish sucking vacuum that slurps up every fish in its path. Not everyone catches a ton of fish every trip. Yeah, there are 100+ fish days, but those are rare, even in "good" years. A lot of people catch a few or get skunked because the weather isn't right, or they don't know where to fish, or they don't have the right bait or presentation.
Minimum size limits are only effective on bodies of water that have high populations of young panfish, fast growth and a lot of fishing pressure. I don't keep a lot of fish, so length and creel limits would not affect me. I would support them,
IF there were evidence there was a problem caused by overharvest and they would be effective on a
SPECIFIC body of water. Implementing them willy nilly can cause stunting, which is
MUCH harder to fix than simply putting a minimum size limit or creel limit in place. Ask those southeastern guys with lakes and ponds full of 5" perch no one wants to bother fishing.
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