shellfish

An oyster or clam is what we call shellfish.

When people talk about seafood, they often mean fish like salmon or cod. But sometimes they also include other ocean creatures with hard outer shells. Shellfish can be anything from clams and mussels to shrimp and scallops. Sometimes a restaurant will have a special section on their menu for shellfish dishes, which might include things like oysters Rockefeller or lobster rolls. These are usually more expensive than the regular fish options because they're considered a treat, but many people love trying different kinds of shellfish when they go out to eat.