While I agree crappie grow much quicker and bigger in the south, I'd like to see the data to support an average 4 year old crappie measuring 16" and weighing 3 lbs in Mississippi compared to 9" and 1/2 pound in pennsylvania. Something tells me your average 3 pounder is a little older than 4 years.
Me, too. The 9" stat sounds pretty spot-on for northern, cold climate crappie. I've seen the statistical work on Minnesota crappie, a very cold environment, and it confirms that sort of length at that age. But, I have also seen Florida stats, warm water/long growing seasons, that don't point to anything close to an "average" of 3 lbs. at 4 years.
Now, I suppose there could be something special about Mississippi.
A bit of hyperbole in the article I'd guess. 3 lbs. crappie, anywhere, are likely statistical outliers, I'd imagine, not average, at 4 years.