[header] How to fillet a mackerel [title] Place the fish onto a cutting board. [title] Fold down the pectoral fin (on the side of body) against the head. [title] Put the blade of your knife behind the folded fin, holding the knife at a slight angle. 
[title] Sever the head and fins from the body in one slice of the knife. [substeps] When you are cutting a mackerel, do not press down with the hand holding the fish.