Bivalve and Shellfish

Bivalve noun - Marine or freshwater mollusks having a soft body with platelike gills enclosed within two shells hinged together.

Shellfish and bivalve are semantically related In some cases you can use "Shellfish" instead a noun "Bivalve".

Shellfish noun - Invertebrate having a soft unsegmented body usually enclosed in a shell.

Bivalve and shellfish are semantically related in crustacean topic. You can use "Bivalve" instead a noun "Shellfish".