How do I prepare and cook a whole fish?

Scaling, gutting and slashing — plus why whole fish is easier to cook well than fillets.

Difficulty: intermediate
Time: 30 min
Read: 2 min
Safety: caution

Short answer

Ask the fishmonger to scale and gut it and most of the work disappears. Then slash the thickest part to the bone so it cooks evenly, and cook until the flesh at the backbone is opaque.

Whole fish is cheaper, better value and considerably more forgiving than fillets — the bones and skin protect the flesh and keep it moist. The preparation looks daunting and is mostly done at the counter if you ask.

Safety

Fish bones and fins are sharp. Handle gills and dorsal fins carefully, and use kitchen scissors rather than pulling. Keep raw fish separate from other foods, refrigerate promptly, and cook until the flesh is opaque and flakes.

What you'll need

Whole fish
Kitchen scissors
Sharp knife
Fish scaler or a blunt knife (optional)

Step by step

Ask the fishmonger to scale and gut it.Free, done in a minute, and it removes the messiest part entirely. Ask them to trim the fins too.
Scale it yourself if you must.Inside a large bag or in the sink — scales go everywhere. Scrape from tail towards head with the back of a knife or a scaler, then rinse.
Check it is properly gutted and rinse the cavity.The dark line along the backbone inside should come away. Rinse and pat dry inside and out.
Trim the fins with scissors.Dorsal and pectoral fins are sharp and serve no purpose on the plate.
Slash the thickest part.Two or three diagonal cuts down to the bone on each side. This is what makes a whole fish cook evenly rather than being dry at the tail and raw at the shoulder.
Season inside and out, and fill the cavity.Salt generously, including in the slashes. Lemon slices, herbs, garlic or fennel in the cavity flavours from the inside.
Cook hot — roast, grill or barbecue.Around 200°C for 20-30 minutes depending on size. Skin-on protects the flesh and crisps well.
Test at the backbone.Push a knife tip into the thickest part next to the spine. The flesh should be opaque and lift cleanly from the bone.

Tips

Look at the eyes and gills when buying. Clear bright eyes and red gills mean fresh; cloudy eyes and brown gills do not.
Serving is easier than it looks: run a knife along the backbone, lift the top fillet off, then lift the whole skeleton away in one piece.
Keep the head and bones for stock. Fish stock takes twenty minutes rather than hours.

Questions people ask

Why slash a whole fish?

It lets heat into the thickest part so the whole fish cooks evenly, and it lets seasoning reach the flesh rather than sitting on the skin.

How do I know when a whole fish is cooked?

The flesh at the thickest point next to the backbone should be opaque and lift cleanly away from the bone.