There are a few fish not affected by the colder water and trout is one of them. As with crappie and smallmouth bass, trout will feed and remain active in colder water.
Trout actually prefer milder temperatures all year long and will move to cooler streams and rivers. Trout, in a natural stream, hold in areas with a current and where there are riffles on the surface to look for bugs and prey to hit the surface. This is why fly-fishing is so productive for landing trout. This is one of the oldest but best ways to fish for trout in a stream or river because of the natural look and presentation of the bait.
Over the years I have gotten to do a lot of fly-fishing for trout and a lot of other fish and most of the time I had a good trip. This is a style of fishing that by simply modifying the rig some you can adapt it to bluegill or bass fishing very easily.
On several bass fishing trips with a fly rod I have caught nice size keeper bass. You also get a much better fight when using a fly rod. Bluegill can be caught one after the other using a fly rod in the summer. I have even hooked into decent size catfish in the lakes by using a fly rod while bluegill fishing. You talk about a fight — that was one!
Fly-fishing is not a fishing style you just start doing. It takes some practice to get used to but is well worth it. If you never tried it you don’t what you are missing.