Fish and Shellfish

Don’t believe the  term shellfish. These edible critters are not true fish.  Some are crustaceans, characterized--and classified--by their hard outer surface  (also called an exoskeleton) and fleshy underlying tissue. Examples include lobster, shrimp, and crab.  Other shellfish, such as oysters and snails, are classified as mollusks, animals with a fleshy body inside a shell. 

 In contrast, true fish have fins and scales, and are sometimes referred to as finfish to distinguish them from shellfish.

From a nutritional standpoint, fish and shellfish are quite similar. Both are excellent sources of protein and are low in fat.