To clean, retaining the head, slit from under the head down to the tail.
Remove entrails by hooking the finger under the throat and pulling down towards the tail. Wash well. A rubber glove may be used for this step.
If the head is not required as with, for example, mackerel and herring, cut it off with a sharp knife before boning.
Slip the sharp knife under the bone on each side of the fish in turn, open and remove the bones.
An alternative method which may be easier for the inexperienced is to turn the fish open-side downwards. Press down on the back with the heel of the hand and loosen the bone.
Turn the fish over and starting at the tail end, place the blade of the knife under the bone and push along the spine to release. Feel the surface of the fish with the fingers to ensure there are no stray bones. The round fish is now ready to be cooked.