When the water gets down in the 30's the threadfin start killing off....Throwing the float n fly is a dead on imitation of the dying threadfin....if youre out on cumberland much during the cold months you will see a lot of threadfin floating and a lot more turned up on their side in the process of dying....the ice just speads up the process and even though the cold didnt last long the ice melting is keeping the water temps down