Clarias catfish have accessory breathing organs that allow them to breathe atmospheric oxygen even when there is no dissolved oxygen in the water. Selling fish alive until sold maintains them in the highest quality until purchased by the final consumer. Keeping the fish wet, either in a tank of water or even under a wet fiberglass rice bag could keep them alive for days as long as they have access to air. But once they die, they deteriorate just like any other fish. Rice bags are available anywhere for essentially no cost. Keeping the bags wet allows cooling of the fish through energy loss through the heat of vaporization. Not all African catfish can breathe atmospheric oxygen but Clarias are far and away the most important, most numerous catfish on the market.