The Northern California Fly Fishing Board

that's a great question. My guess is that it won't have much of an effect on the hatches other than they might interpret it as cloud cover. However, if it's very smoky on the river, it will probably effect how the bugs react once they are out of the water. If you're thinking of fishing this weekend i would shoot for a river tucked deeper into the canyon. (as opposed to the stan at knights ferry) it will be less smokey.

P.S. there is a possibility that everything i've just said is completely wrong.