An apparatus for cutting free the flank bones of decapitated, slaughtered fish with opened abdominal cavities which are transported on transport saddles as supporting bodies for securely receiving the fish in their abdominal cavities, comprising an upper bone guide, a lower bone guide and a separating assembly for releasing fish fillets from the flank bones, wherein the separating assembly, which can be brought from a standby position into a working position and vice versa, comprises a fish fillet from fish flank bones separating means having at least one cutting edge and having a corresponding counter-surface, characterised in that a covering element, for covering regions of the at least one cutting edge of the separating means located in an effective region of the fish fillet from fish flank bones separating means inside the fish, is assigned to the separating means, and the covering element is designed and configured such that the covering element can be automatically adjusted with respect to the position of the covering element in relation to the fish fillet from fish flank bones separating means.