Fresh mussels can be stored in the refrigerator for several days before cooking and eating them. The key is to package them carefully so that they don't go bad. Mussels require some moisture to remain fresh, but should not be immersed in liquid for extended periods of time. If you don't plan to eat the mussels within a few days, you can also cook and freeze them. Storing mussels in the freezer will keep them fresh and edible for several months.
Storing Fresh Mussels in the Fridge
Remove the mussels from their mesh bag and place them in a bowl. Make sure the bowl is large enough to contain all the stored mussels, so that none are peeking over the edge.
Soak a dish towel with cool water and wring it out until it is just damp. Drape the dish towel over the top of the bowl, covering the opening.
Place the bowl of mussels in the refrigerator. Make sure to keep the towel damp. A small amount of liquid will drain from the mussels into the bottom of the bowl. Pour out that liquid each day to keep the mussels fresh.
Remove the mussels from the bowl when you're ready to cook them. Transfer the mussels to a colander and rinse them with fresh water to remove any residue from their shells before cooking them. It you're planning on freezing the mussels, reserve the cooking liquid after they're finished.
Storing Cooked Mussels in the Freezer
Remove the meat from cooked mussels' shells and place it in a freezer-safe, airtight container to keep the meat from becoming freezer burned.
Completely cover the mussels with the broth that they were cooked in, leaving about an inch of space at the top of the container.
Store the mussels in the freezer for up to four months.