Two fish being filleted

How to fillet a fish

Watch our video guides to learn the correct techniques for filleting round fish, such as mackerel and sea bass, as well as flat fish like plaice and sole.

Master the classic cookery technique of preparing a round or flat fish with our easy video tutorials and step-by-step information. We show you how to trim the fins, then remove the innards and bones in order to extract as much of the fillet as possible. It’s important when buying fish to check that is fresh, so we’ve also included some tips for what to look out for.

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Equipment required:

  • Chopping board
  • Large knife
  • Kitchen scissors
  • Filleting knife or medium knife with flexible blade (as sharp as possible)
  • Tweezers or pliers

How to fillet a round fish

  1. Remove head by cutting at an angle just under the fins near the head on each side, and then under the fin on the underside.
  2. Snap the head off, removing any innards.
  3. Make an incision along the skin on the back of the fish, to one side of the dorsal fin.
  4. Place the tip of the knife in and run from the head to the tail, along the bones. Midway along the fish, place the knife down and through to the underside of the fish, and then run the knife along the whole fillet, to the tail. Remove the fillet by stroking the knife under the fillet from the mid point of the fish, towards the head, then remove it from the frame. Repeat on the other side. Trim skin around the fillets to neaten them.
  5. Pinbone the fillet, using tweezers to pull out the sturdy bones from the centre of the fillet, or cut along either side of them and pull the whole strip of bones out.

How to fillet a flat fish

  1. Remove the head by scoring through the skin with a sharp knife and then using scissors to cut through.
  2. Using a flexible fish filleting knife, cut down the central line until you come into contact with bone. Cut a small incision across the tail.
  3. Rest the knife on the backbone and draw it down, listening for the knife pinging along the bones, repeating until you begin to get underneath the fillet.
  4. Use a long sweeping action to stroke the fillet from the bone and pull the fillet away. Repeat on the other side, then turn the fish over and repeat until you have four fillets.
  5. Skin the fillets by placing skin-side down and turning the fillet so that the narrowest side is towards you. Hold the fillet with one hand, then position the knife so it’s nearly flat with the board, but slightly angled so you’re cutting down towards the skin. Use a sawing motion, trying not to cut into the flesh as you go.
  6. Cook as desired. The fish can be simply fried in butter on a high heat, after being rolled in seasoned flour.

How to check if fish is fresh

  • The fish should smell pleasantly of the sea – if it smells fishy, it may be off.
  • If you press the fish lightly with your finger, the flesh should spring back. If it remains, the fish is no longer fresh.
  • The eyes should be bright and shining – dull eyes mean the fish is past its best.
  • The fish skin should be firm, bright and metallic if fresh. Any discolouration or dull spots indicate the fish has aged.
  • If you pull the gills open, the insides should be bright pink-red – a dark bluey-purple colour means the fish isn’t fresh.
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Put your fillets to good use in a range of delicious fish recipes. Also watch our video for how to prepare a whole fish and guide on how to prepare crab.