Before preparing a whole fish, it is important to ensure it is fresh. The gills should be moist and bright red, the eyes full, shiny and slightly bulging, and the skin glowing, pearly, taut and adhered to the flesh which should be firm and elastic. The scales should be shiny and still firmly attached, and the fish should have a pleasant smell.
Fish is prepared in four stages: scaling, trimming, gutting and, if necessary, filleting. Fish is generally scaled before it is gutted, as it is easier to scale if the belly is slightly rounded. The tools used are a fish scaler or the back of a knife. One hand holds the fish by the tail and the other removes the scales by moving the scaler at a 45 degree angle along the fish, working from the tail towards the head.
Trimming fish involves removing the fins. It is often necessary to wear gloves to do this in order to prevent injury, as the fins of some fish can be very sharp or secrete venom.
There are several methods for removing the guts. The easiest way is to extract them is by cutting the stomach open. It is also possible to make an incision of one or two centimetres near the gill.
Filleting is definitely the operation which requires the most dexterity. Round fish produce two fillets while flat fish produce four. These tasks are often performed by the fishmonger or carried out on board factory ships where fish is processed, packed and frozen. It is also possible to buy fillets, cross-section slices (steaks) or pieces of fresh or frozen fish. The best way to defrost fish is to place it in its original packaging in a refrigerator for between 18 and 24 hours.