If you are an avid floater of summer rivers, one the best times to get a feel for a river is to float at mid-day when the water is low and clear and the sun bright and high (admittedly not the best way to catch fish).
In these conditions, especially if you can stand up with your polarized glasses, you can get a very good feel for the structure and habitat of the river. You will see a lot of fish and subsurface life and get a better understanding of where different species hang out.
Keep an eye out for catties as they are numerous in many of our mid sized to larger rivers (I see them much less frequently in small creeks). After awhile, you will note that catties relate to woody cover. When you drift over a submerged log, pay careful attention to detail and you will start to see catfish' tails sticking out from under them. They also like river grass clumps. After awhile, you will also note that catties tend to school up in groups of three to maybe a dozen fish, usually adults in the same size range. When you see such a group in faster current, they are likely on patrol for food. Groups that are laid up in cover or on a sandy bottom pot-hole are less likely to eat. But they stick together. If you catch a cattie, keep fishing that spot for awhile as you may get additional fish.
I remember one evening at Harper's Ferry where I was fishing a chute of fast water between two giant boulders drifting a crayfish pattern for bass... and caught cattie after cattie. There was a group of them laid up in that current like trout waiting for nymphs.
