A clam, oyster, or mussel can remain alive and healthy for days, and sometimes a week or two, out of its natural seawater environment because it can tightly clamp its shell. By doing so, the mollusk maintains its own liquid eco-environment within its protective case. A scallop, on the other hand, cannot snugly shut its two shells. Once pulled from the water, its juices run out and the coming of the three Ds - death, desiccation, and disease agents - is imminent. Professional scallop gatherers, therefore, usually shuck the bivalve on the boat, discarding the quick-spoiling viscera.
** Asian Recipes