I've seen pirahnas down to about 60F and up to about 95F, but that was only for short periods of time, prolonged life in those temps would result in death. It is possible that it was just released, and in search for food as temp decreases (to a certain point) to keep themselfs alive, bit a hook and got caught. Here in Iowa they have caught pacus in the lakes but that is rare.
As for releasing an oscar in NJ, yes that is irresponsible, but chances are that at the time they were releasing it, he had no idea of what he was doing.