Shoe,
No reason to go round and round...but take a look at the pictures I posted.
I didnt high-grade those perch in either picture, the first is a 50 fish limit, the first 50 I caught. Same with the other picture.
The smaller fish in the first picture were almost entirely males, but the same age class of fish as the larger females. There was only 1 major age class of perch in that lake...and they were caught out in mainly 2006 and 2007. What was left of the age class was blasted in 2008, the last year I did real well on perch. It was a gradual change, in 2006, I rarely spent more than an hour to find a school of perch and limit. In 2007, I typically had to fish a half day to get on them and limit. In 2008, I limited one time and it was an all day deal to get on them. Once you located a school of perch, you could either catch them all or limit on them.
The reason you saw no major change in size is that there wasnt different age classes, everyone was pounding the same fish/age class.
The water conditions probably did contribute to unsuccessful spawning of the perch in those years, but the only disease that particular age class suffered from was filet knives...