Here are some tips on buying fresh shellfish. Fresh oysters, clams, scallops, mussels and cockles should have tightly closed shells or they should close their shells when you tap them. Choose shellfish that smells mild and fresh. Refrigerate it immediately and keep it cold (below 4°C). It is also important to separate your shellfish from other food in your refrigerator to avoid cross-contamination. Raw shellfish can carry bacteria or toxins that can cause food-borne illness.