in a method for manufacturing fish tail pieces of the same length a fish conveyed transverse to its longitudinal axis in conveying troughs is displaced in the conveying troughs by a pulling engagement of its tail fin and is transversely cut after reaching the desired position . the device for carrying out this method comprises a gripping device in the form of a circular disc with a number of pincers which run with the trough conveyor and clampingly seize the tail fins . the diverging movement of the pincers which , due to the circular path , diverges from the conveying direction of the trough conveyor effects the displacement of the fish , this displacement being ended by the severing of the tail fin by means of a circular knife whose position can be adjusted .