Electo-fishing can be easily done without harming the fish. I doubt those are threadfin shad and they are likely gizzard shad. Threadfins will usually die during winter water temps of many lakes. While threadfin shad die at 42-degrees F., gizzards can withstand cold water, under the ice. But when their density is too dense and competition for food causes them to decline, they will die from stress in cold temperatures.
