I don't think fish get near as lethargic as some might think. Their metabolism might slow down but not the ability to swim. I caught bass last year in less than a foot of water with ice on the lake. And I could see them come hit the lure. And they were anything but slow moving. Fishes is a fish in that regards. Also, what is the odds of so many fish being at the one relatively small area of the intake? Over acres and acres of the lake. I'd think you could damp a boat out from the intake if that was the case and catch fish all day.