Abstract: Frozen roundfish, such as codlike white fish, salmon or trout, having a substantially straight shape is longitudinally split centrally of the fish so that the main portion of the vertebral column is removed, and each of the frozen fish halves are subsequently cleaned and searched for impurities, following which the still frozen fish pieces are portion-packed and freeze-stored. With the view of positioning the fish during the splitting it may be frozen in a faceted shape or with raised fins. When the whole, frozen fish body has been positioned with its vertical plane of symmetry in a well-known position, the fish may be securely held by means of fixing means (59) having a part (68) consisting of a fluidum absorbing and flexible material that may be locked in abutment on the exterior of the frozen fish and freeze firmly thereto. The grip of the fixing means in the fish is so strong that it will not be broken by the splitting of the fish.