Cooked mussels

Shellfish is a culinary term for some aquatic invertebrates used as food: molluscs, crustaceans, and echinoderms. It is not a scientific term, and its use may vary from place to place.

Both saltwater and freshwater invertebrates are considered shellfish. Molluscs commonly used as food include the clam, mussel, oyster, winkle, and scallop.

Some crustaceans commonly eaten are the shrimp, prawn, lobster, crayfish, and crab.

Echinoderms are not eaten as commonly as molluscs and crustaceans. In Asia, sea cucumber and sea urchins are eaten.