If you were catching them in shallow water prior to this freeze, I would assume they are not far from there now. Water temps were already in the 30's. I can remember a time we fished buckbrush and caught crappie a couple feet deep after breaking the ice around the brush. The sun would heat the bushes and the water was a couple degrees warmer around the bushes. It only takes a couple of degrees of water temp to move fish. All of that said is assuming you are fishing a shallower lake.