It's a blitz of sorts. There are so many flies on that trout, including the big boys, tend to lose a little bit of caution and come to the surface readily for the calories. But smallmouths react the same way, as do fallfish, white perch, sunnies, and any other species that might be in the river. I've even seen people catch white catfish on this hatch in Pennsylvania. :eyecrazy:
The fishing isn't too tough...a size 12 or 14 White Wulff on about 5X with a dead drift seems to work just fine. If there's just too much meat on the water and the fish don't notice your fly, a quick skate or two can draw their attention.