Whether Dungeness, king, horseshoe, rock, blue or snow, all crabs are caught alive in pots or nets -- and should be kept alive until you are ready to cook them. How you store the crabs after pulling them out of the water largely determines how long they stay fresh before boiling them for consumption.
The Sooner the Better
Crabs should be cooked as soon as possible after being caught, preferably within a few hours. Store and transport them cool, damp and alive. Place crabs in an ice chest, cover with a towel or burlap bag soaked in salt water, then topped with another layer of ice. Cook while still alive, or kill and clean them just prior to dropping into boiling water. If you must kill them earlier, they will generally stay safe to eat for a few hours, according to the Washington Department of Fish and Wildlife.