All of sudden..Flatheads

My house on the Rock River in N. Illinois has been in the family since 1953.
I don't remember ever catching anything but Channel Cat with the occassional
Flathead or Blue and nothing over five pounds or so. This year, however, in
the stretch of river that runs from my place to a couple of hundred yards
upstream, they've been catching 25 to 55 pound Flatheads. I noticed since
last year an abundance of Redhorse Suckers and Sheepshead. Could it be the
increase in food supply has caused the increase in Flathead size? They're
being caught on Bluegills which aren't even naturally in the river. Other
things of note this year...The river is unusally low due to the drought,
making the stretch in front of my place one of the deeper parts of the river
(maybe, therefore, the Flatheads are congregating here). Also the river is
cleaner than it used to be when I was young and we've also had extra hot
weather this Summer. And finally, due to the low water (and I suspect, the
cost of replacement propellors) there hasn't been near as much pleasure boat
traffic this Summer.
Unfortunately, I haven't caught mine yet (just an 8lb Blue the other night)
but I'm trying.

When I went down the other night, my neighbor called out that he had another
big one on. I haven't had a chance to see the pictures yet but I heard his
wife call out "Oh, my God" when he got it into the net.

Tom