Is it a good idea to fish small rivers in fall for Flatheads when cold weather is moving in? Water is cooling down fast and the little river i fish at its deepest hole is about 12 ft deep average is 3-4ft. do the fish stay there even during winter or do the head down into the lake where the water is deeper? Planned to give it a shot this weekend in the small river but not sure if i should head to deeper water since the temperature is dropping. The lake temp is about 68 degrees river not sure prob 55-60.