Shellfish's a culinary and fisheries term for exoskeleton bearing aquatic invertebrate used as food, including various species of molluscs, crustaceans, and echinoderms. Familiar molluscs enjoyed by humans include many species of clams, mussels, oysters, winkles, and scallops. Some crustaceans commonly eaten are shrimp, prawn, lobster, crayfish, and crabs. Echinoderms aren't as frequently harvested for food as molluscs and crustaceans, but sea urchin roe's quite popular in many parts of the wor… (More on Shellfish)