The full guide
Read straight through, or use the seafood notes above to keep buying, cooking and serving simple.
How to gut a Fish
When you buy fish from a fishmonger they are usually already gutted. If you catch your own fish or buy fish that have not already been gutted it is important to do this to remove the guts.
The demonstration we have shown here is gutting a mackerel but the method is the same for all round fish.
Kitchen kit for this guide
Seafood prep and kitchen kit chosen to make the guide easier to use.
How to gut a mackerel: step by step
Mackerel are among the easiest fish to gut, and once you have done a few it takes a minute or two. You need a sharp knife, a board and cold running water or a bucket of clean seawater.
Step 1: Rinse the fish. Mackerel scales are tiny, so there is no need to scale it.
Step 2: Hold the mackerel belly up and push the tip of the knife into the vent, the small hole on the underside towards the tail.
Step 3: Cut forwards along the belly to the point between the gills, keeping the blade shallow so you do not cut into the guts.
Step 4: Open the belly, hook the guts out with your fingers and pull them towards the head. If you are cooking the fish whole, cut out the gills or take off the head.
Step 5: Run a thumbnail or teaspoon along the backbone inside the cavity to scrape out the dark bloodline, which can taste bitter if left.
Step 6: Rinse the fish inside and out under cold water and pat it dry with kitchen paper. Wash your hands, knife and board in hot, soapy water afterwards.
Do you have to gut mackerel straight away?
Ideally, gut mackerel the same day and as soon as is practical. Mackerel are oily and spoil faster than most fish, and the belly softens quickly in warm weather. If you cannot gut them on the spot, chill them straight away: put them in a cool bag with ice packs, keep them out of the sun and gut them as soon as you get home. Then keep them in the fridge at 5°C or below and eat them within a day or two, or freeze them.
Should you gut mackerel before freezing?
Yes. Gut, clean and dry mackerel before freezing, or fillet them first if you will want fillets later. Wrap them tightly or freeze them in sealed bags with as much air pressed out as possible. Oily fish keeps its quality for less time in the freezer than white fish, so use frozen mackerel within a couple of months for the best flavour, and thaw it in the fridge.
How to fillet a mackerel
Lay the gutted mackerel on its side. Cut behind the head and gill down to the backbone, then turn the knife flat and run it along the backbone towards the tail, keeping the blade pressed against the bones, and lift the fillet away. Turn the fish over and repeat. Trim off the thin belly bones with a shallow cut, then run a finger down the middle of each fillet to find the pin bones; pull them out with tweezers or cut a narrow V either side to remove them in one strip. The videos below show the method on a mackerel, a plaice and a whiting.
How to gut a plaice and other flatfish
A flatfish keeps its guts in a small cavity just behind the head. On the white underside, make a short cut just behind the head, hook the guts out with a finger and rinse the cavity. Trim the fins with kitchen scissors if you like. Plaice, dab and flounder can then be cooked whole or taken off the bone as four fillets, as shown below.
Caught your own? Our mackerel fishing guide covers catching them, and getting rid of fish smells helps with the clean-up afterwards.
How to Fillet fish
Filleting a fish is removing as much of the flesh as possible but leaving all the bones behind. This is a preferred method of serving fish to people not used to eating fish as many people find sifting through bones or finding bones in their dinner very off putting. We have demonstrated how to fillet three different types of fish in our videos. The basic method is the same in that you make an incision just behind the pectoral fin and then run the blade horizontally next to the main central bone towards the tail of the fish.
For larger fish like cod, pollack and haddock this will take several passes of the knife gradually working your way towards the back of the fish.
Filleting is something that takes practice and unfortunately, until you master it, your family may well have to endure the odd bones! It is worth persevering though as a lovely boneless fillet of freshly caught fish is a treat for anybody.
Filleting a Mackerel
Filleting a Plaice
Filleting a Whiting
Skinning a Fish Fillet
How to remove the skin from a whiting fillet
If you are planning on freezing your fish to eat at a later date then it is best to leave the skin on when your freeze it. When you remove it from the freezer, run it under the tap for a few seconds and then the skin will peel off easily.
If you want to skin it straight away then you will need to run a filleting knife between the flesh and the skin starting from the tail end. While doing this hold on tightly to the skin at the tail end. This is demonstrated in our video below.
Knives
If you go into an angling shop you will have a choice of knives ranging from bait knives, gutting knives, filleting knives and penknives. It is not necessary to have all these different types of knife. A filleting knife can be used for cutting bait, gutting and filleting and the only other knife needed would be a small penknife for cutting fishing line and small strips of bait.
A good filleting knife should have a thin flexible curved blade and the blade should be at least 6" (150mm) long. Some filleting knives have sheaths to protect both blade and fingers and some have buoyant handles so that they float if dropped overboard!
Please be aware of the current laws regarding knives and where they may be used. We only sell knives to people aged over 18
Common questions
- How do you gut a round fish?
- Slit the belly from the vent up towards the head, lift out the guts, and rinse the cavity clean. The method is the same for all round fish, such as mackerel, whiting and pollack.
- How do you fillet a fish?
- Make an incision just behind the pectoral fin, then run the blade flat along the central backbone towards the tail, lifting the fillet cleanly off the bones. Repeat on the other side.
- How do you skin a fish fillet?
- From the tail end, run a filleting knife between the flesh and the skin while holding the skin tight. If you froze the fillet with the skin on, a quick rinse under the tap lets the skin peel away easily.
- What knife do you need to fillet fish?
- A thin, flexible, curved filleting knife with a blade at least 6 inches (150mm) long. One good filleting knife will handle gutting and filleting; you do not need a drawer full of blades.
- Do I need to gut fish straight away?
- Gut it the same day and as soon as is practical, especially oily fish such as mackerel, which spoil quickly. Until then, keep the fish chilled in a cool bag with ice packs and out of the sun.
- How do you clean a mackerel?
- Mackerel have tiny, soft scales, so you can usually skip scaling and simply rinse the fish under cold water. Slit the belly from the vent to the head, lift out the guts, and scoop away the dark bloodline along the backbone with a thumbnail or teaspoon, as mackerel have a pronounced one that can taste bitter if left. Take care not to burst the gall bladder, then rinse the cavity and pat dry.
- Which fish need scaling before filleting?
- It depends on the fish and how you plan to cook it. Large-scaled fish such as grey mullet, bass and sea bream want scaling if you are keeping the skin on for grilling or roasting, while small-scaled fish like mackerel and plaice rarely need it. If you intend to skin the fillets, you can skip scaling altogether, as the scales come away with the skin.
- How do you remove pin bones from a fish fillet?
- Lay the fillet skin-side down and run a fingertip along the centre line to feel the row of fine pin bones. Grip each bone close to the surface with fish tweezers or clean pliers and pull in the direction it points, usually towards the head, so the flesh stays intact. Pin bones are most noticeable in oily round fish such as salmon, herring and larger mackerel.
- What is the difference between filleting a flat fish and a round fish?
- A round fish such as mackerel or bass gives two fillets, taken by running the blade along each side of the backbone from head to tail. A flat fish such as plaice or sole gives four smaller fillets, two from the top and two from the bottom, cut from a central incision down the backbone out towards the fins. Flat fish take a little more patience but the principle of keeping the blade against the bone is the same.
- How do you cook a whole mackerel once it is gutted?
- Once gutted, score the skin three or four times on each side, season inside and out, and brush with oil. Grill, barbecue or pan-fry over a medium-high heat for around three to five minutes per side, turning only once so it does not break up. It is done when the flesh is opaque and flakes easily and the skin lifts away cleanly.
- Do you gut mackerel before freezing?
- Yes. Gut, rinse and dry mackerel, or fillet it, before freezing. Wrap it tightly, use it within a couple of months for the best flavour and thaw it in the fridge.
- How do you gut a plaice?
- Make a short cut on the white underside just behind the head, hook out the small bundle of guts with a finger and rinse the cavity. Plaice can then be cooked whole or filleted.
