Thank you to our folks in Iowa DNR, Spent a lot of time at the hatchery at rathbun and learned so much.
http://adventure.howstuffworks.com/outdoor-activities/fishing/fish-conservation/fish-populations/fish-stunting1.htm

LOL Steve not everyone is a
Superintendent of Public Works.

Limit was generated by fisherman, Nothing to due with fish biologist in iowa. Water quality should be more of a issue right now then limits of panfish. Metals, pharmaceutical drugs flushed down the drain, drainage from stock yards coming right out of your faucets, And is getting worse. The meat of a fish is not what it use to be. Thats another reason we made our own lakes to keep our fish as healthy as possible.
I would like to give a heads up about bait shops I have discussed how this has affected them, And yes it has. Due to this small limit people do not travel and fish in iowa as much as they did. That hurt fishing license from out of states folks. I caught one fellow and he told me with gas prices and hotels, its just too much to travel 100 miles for 25 fish. So to the fellows that wanted the limit set you won.

Crappie are very prolific and will overpopulate a small lake very quickly. They can crowd out other species like bass and cause both species to be stunted. Crappie don’t have a really long life cycle, so hundreds of thousand die out annually, the ice out in the north also kills thousands, We also have DNR that can produce annually millions of fries at the hatcheries, I have 6 ponds that I have done yearly reports, and this is a serious issue when the fish are not removed. Disease has rendered a prolific effect on one pond where none were removed. I also have one pond that only one crappie populated with 3 males, it with 2 years has been over populated. I have numerous other species that we have introduced to keep our records in check to see how we can keep the fish in from over populating and still keep the fish from being stunted. I can keep going on and on, but so far if you want to put a limit on fish, Do a length limit rather then a quantity. I am tell you one female can over populate a pond and if you allow it to go serious issues will evolve. Thanks and keep a wet line and better yet take as many kids fishing as you can.