I witnessed something a while back that I have never seen in all my years on the river, and have yet to figure out what the heck was happening. We were sitting on the riverbank, the river is a smaller river, average about 30 to 50 yards wide, with some deep holes around 30', but mostly between 10 - 15' with a lot of shallow riffles, with a decent current most places. The hole we were fishing was about 50 yards below a riffle that is probably a quarter of a mile long, and the water where we were fishing was probably between 5 - 12' deep depending on where you cast. Just before dark, before we even fired up the lantern, we started to notice it. Flatheads, by the DOZENS, were swimming/floating by very slowly with their mouths gaped open, pointing straight up at the sky! They were not acting like they were in distress or anything, and we caught fish later that night off the bottom, so I don't think they were in trouble or anything. This went on for an hour or more. My brother and I could not figure out for the life of us what was going on. There was no moon that night, and it was well before the spawn, probably mid June or so. Any ideas what was going on??