In bodies of water that have a fair population of yellow perch, I've had outstanding success using cut pieces of yellow perch. I'm assuming there are perch in Chatfield, so maybe if you can catch one, that will work for you. The perch work well because even a small one (5-8") is much thicker than a comparable sized bluegill. Cutting them into cross-sectional pieces yields a nice, "chewy" piece of bait.
To get a piece, what I do is cut the head off of the perch (you can use this for bait but I usually throw it out into the water -- poor man's chum, though not in Colorado as I believe it's illegal). Repeat cutting in this direction, leaving about 1 - 2" (depending on the size of the cats) between cuts as you work your way back to the tail. You should end up with a bunch of pieces resembling a rectangular chunk of meat that is thicker on top (where the fish's back would be) and thinner at the bottom (where there's less meat due to the internal organs). For the chunks in the middle of the body, rip out the dorsal spines/fins -- they are sharp and may cause the fish to drop the bait quickly.
The last thing you do before you hook the bait is scrape about 85% of the scales off -- for whatever reason, this seems to increase my catch rate. The ones that don't come off will be loose and fall off in the water, which helps disseminate a scent trail. As for hooking the bait, run the hook through the "top" of the piece (the section from the fish's back) if you're using a wide-gap hook, otherwise hook the portion from the fish's stomach (it is thinner).
It's weird, the bait doesn't smell particularly strong, but I've left pieces in shallow clear water buried in the weeds and watched 5-8lb. cats cruise the shallows just before sunset and dig them right out. An amazing thing to see really.