ePiC is right, they get rid of their large brooders at the end of the summer.
But forget it. You don't want those, you want fish that were put in at a smaller size some years ago, and which have survived and grown to the size you want, and have become wild fish -- no longer stockers. Quite a few lakes have those.
I was out at Lon Hagler Res. around September or so last year when the truck stopped by and tossed out about 400 rainbows in the 22-24 inch range. It was ridiculous. These fish were not only totally out of shape with no muscle tone, they were also unsophisticated and dumb as a stick. They didn't even know how to feed themselves in the wild. I went right over to where they put them in, and caught/released a couple just to make sure I knew what they were.
It was no challenge, believe me. As I walked around the shore, I could see little wakes beside me. Those fish were following me! They wanted me to feed them!
I don't know why, but the whole thing just made me feel bad, somehow. It was just wrong. I guess I felt sorry for the fish, and that's not something that happens very often.
Nothing wrong with targeting nice big trout, but the ones you want have survived past the stage of being "stockers" and have grown up in the wild.
I hear you W.E. That is sad in a way...I could feel sorry for the fish as well.
Horsetooth reservior has some big (now wild) rainbows in it. I'm sure most of the stocked lakes and reserviors in colorado have the fish that become smarter than the average stocker and survive to become big 'wild' fish. they also get harder to catch. it's our job to go fool them.;
I was at Chatfield last summer when the truck showed up. They put 4000 8-12 inch rianbows in. Dumbest fish you ever saw. They would hit on anything. a lot were caught within minutes of being released by folks who followed the truck in. 4 hours later I caught 4 or 5 myself in the cove they were released in, in about 5 minutes........Dumb fish.
Last year, the week before Memorial Day, I took the week off and somehow unintentionally ended up following the stocking truck. Caught rainbows one cast after another at Georgetown, then saw the truck at Cherry Creek, then at Jackson. Figured they were stocking for the weekend. If you want stockers, this time of year they're going to be 8-12 inches and wait before the holiday.
I tend to prefer the ones that have been in for a while as well. You can really tell the difference not only in the catching, but the meat will be pink instead of white and much firmer and more tasty.