There are MANY catfish in the main channel. In the upper canyon they'll be small but those that are big enough to skin (8-10") are good eating with a little tobasco or bacon. You might occassionally get one bigger, but not more than a pound or so and usually only half that. Down in Grey Canyon there are some deeper holes and bigger fish. In the upper canyon nightcrawlers on short-shank #10 hooks with slip-egg sinkers work best, but they'll take lunchmeat, cheese, whatever. In the big deep holes I hear mice work well. Catfishing is great for the kids. We had a contest and the winner caught five (5) fish on one (1/3) of one nightcrawler before having to re-bait. If you find a school you'll be hauling them in right and left.
There are small trout in Rock Creek. My buddy caught 3 a couple weeks ago in under an hour. But they are small. Creek's not big enough to support larger fish.