Classification of Fish

Fish are broadly classified as FINFISH and SHELLFISH.

Finfish

White Fish

White fish are sometimes referred to as "lean fish" because all the oils are contained in the liver, which is removed during gutting. White fish are further sub-divided into:

• Round White Fish
  Examples include cod, haddock, hake and pollock
  
• Flat White Fish
  Plaice, lemon sole, brill, turbot, black sole are common examples of this category
  
• Cartilaginous Fish
  Ray, rock salmon and shark are examples

Oil-Rich Fish

Oil-rich fish are so called because the oils are distributed throughout the flesh of the fish. Mackerel, herring, salmon and trout are common examples.

Occasionally you will find fish classified in a different way:

Demersal
Demersal fish are those which live on or near the sea bed. Round and flat white fish fall into   this category.

Pelagic Fish
Pelagic fish swim in mid-waters or near the surface. Oil-rich fish such as mackerel, herring and tuna are common examples.

Shellfish

Molluscs
Molluscs can be divided into three categories:

• Uni-valve Molluscs
  Uni-valve molluscs are those with one shell – periwinkle and whelks.
  
• Bi-valve Molluscs
  Bi-valve molluscs are those with two shells hinged at one end – mussels, oysters and scallops are good examples.
  
• Cephalopods
  This type of shellfish has no outer shell, but just a single internal one called a pen. Examples include squid and cuttlefish.

Crustaceans

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