Types of Fish
Fish are broadly classified as Finfish and Shellfish.
Finfish are divided into white fish and oil-rich 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
Examples include 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 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 and Pelagic Fish. Demersal fish are those which live on or near the sea bed. Round and flat white fish fall into this category. Pelagic fish swim in mid-waters or near the surface. Oil-rich fish such as mackerel, herring and tuna are common examples.
Shellfish are broadly divided into two main categories: Molluscs and Crustaceans.
Molluscs can be divided into three categories:
- Uni-valve Molluscs
Uni-valve molluscs are those with one shell – periwinkle and whelks.
- Bi-valve molluscs are those with two shells hinged at one end – mussels, oysters and scallops are good examples.
This type of shellfish has no outer shell, but just a single internal one called a pen. Examples include squid and cuttlefish.
Crustaceans are more mobile creatures with hard segmented shells and flexible joints. Examples include prawns, shrimp, crab and lobster.
Yuor local fishmonger is an expert and will be able to advise you what fish is plentiful and good value for money.
Choose whole fish with bright, prominent shining eyes, bright red or pink gills, distinct skin colour and above all a clean fresh ‘sea smell’. Fillets should be translucent with no sign of discolouration. Remember to get your fish into the fridge as soon as possible – remember it’s highly perishable and must be kept cool.
If the task of preparing a piece if fish is daunting, your fishmonger will be happy to fillet or skin the fish for you.
Fish can be offered for sale prepared in a number of different ways:
Whole ungutted fish: Whole fish should not have burst bellies as this is an indication of spoilage.
Gutted fish: Gutted fish should be free of all gut pieces, with clean washed gut cavity. The head may or may not be left on. If the fish is cooked "head-on" the gills should be removed as should every trace of blood along the back bone.
Steaks and Cutlets: Steaks and cutlets are made by cutting across the backbone of the fish. Steaks and cutlets should be about 2.5cm/1 inch in thickness. All traces of blood must be removed from steaks/cutlets. Steaks/cutlets should be neatly cut.
Block fillet/Butterfly fillet: With this type of fillet the flesh is cut from both sides of a fish with the two pieces remaining held together by the skin. Small whiting, herring and mackerel are often filleted in this manner.
Side/Single fillet: This is a slice of flesh removed from one side of a fish by a cut made parallel to the back bone. All fins and bones, with the exception of pin bones, are removed. Cod is usually filleted in this way.
Darne: A darne is a portion of a fillet cut perpendicular to where the backbone used to be. Salmon is often prepared in this way.
Ray: Normally sold as wings with the skin removed.
Monkfish: Often the head is removed and just the tail presented. The skin is normally removed.
Rock salmon: Difficult to fillet and skin. Normally it is presented for sale in lengths (filleted and skinned) with just the central cartilage remaining.
Squid: Usually presented with head and tentacles removed and body opened out resembling a triangular shape.