Being a long time muskie fisherman, I can tell you guys for certain that some flatheads do feed in very cold water. Last week, just before freeze up, I was at Salt Fork lake with my buddy, and as usual we were trolling for muskies. The water surface temp was 37.7 degrees. We were trolling at a GPS speed of 4.2 mph when this 34 inch flathead hit lure!! This certainly was not a huge suprise to us, because it made the 3rd flathead that we had caught accidentaly in the last 2 weeks out. I also know of 2 other small flathead caught by saugeye fishermen recently! I have no idea how to target these fish this time of year, but I can tell you that they will eat during the coldest of months. They may not eat much, but they do eat.