Being from the mid-west when we talked about ‘fish’ we were talking about bullheads, walleye, crappie, northern, and we’ll throw in catfish. Out here on the east coast it’s different.
Seafood is a general term but there are differences between fish, crustacean shellfish, and molluscan shellfish. Fish have fins but no legs and no shells. Crustaceans are aquatic animals with jointed legs and a hard shell. mollusks are not fish but aquatic animals with hinged, two-part shells, spirals shells, or no recognizable shells. Here are examples.
Oysters and clams
Squid and Octopus
Keep your fork