A fish fillet board has a clamp whose jaws have a horizontal line of action extending substantially parallel to the work surface of the base of the board. Thus, when the jaws hold the fish on its side against the base, they grip the fish by its lower lip to partially paralyze the fish and render it immobile. The clamp may be designed to be quickly and easily attached to and removed from the base, as well as inverted, so that the fish may be flipped over during filleting without releasing the clamp from the lower lip of the fish.