Live mussels (without shells removed) should be stored in open containers in the fridge, loosely covered with clean, damp paper towels or cloths to prevent them from drying out. The optimum storage temperature is 4-8°C. Temperatures of 1°C or lower (especially freezing temperatures less than 0°C) can kill shellfish.
Do not store shellfish:
In airtight containers (boxes or bags) because they need to breathe
In water or directly on ice since the fresh water may drown them
Discard mussels, oysters, clams or any other live shellfish if their shells crack or break
Discard any shellfish if the shells are open and do not close when you tap them - live shellfish will "clam up" if their shells are tapped