Shellfish are broadly divided into molluscs like mussels, oysters, and scallops, and crustaceans like shrimp, crab, and lobster. Finfish are divided into whitefish like cod and haddock that contain oils in the liver, and oil-rich fish. Whitefish are further subdivided into round whitefish such as cod, haddock, hake, and pollock.

1. Fish Facts - Fish
Classification
Jamie Bellingham Y7 2011

2. Shellfish
• Shellfish are broadly divided into two
categories—molluscs and crustaceans

3. Molluscs can be divided
into three categories:
• Uni-valve molluscs have one shell—
periwinkles, whelks and limpets. These
molluscs can be found on the seashore.

4. Bi-valve molluscs
• have two shells hinged at one end—
mussels, oysters and scallops.

5. Cephalopods
• have no outer shell, just a single internal
one called a pen. Examples include squid
and cuttlefish.

6. Crustaceans
• are mobile creatures with hard, segmented
shells and flexible joints. Examples include
prawns, shrimp, crab and lobster.

7. Finfish
• Finfish are divided into whitefish and oil-
rich fish.

8. Whitefish
• are sometimes referred to as "lean fish"
because all the oils are contained in the
liver, which is removed during gutting.

9. Whitefish are further
sub-divided into:
• Round Whitefish—Examples include cod,
haddock, hake and pollock.