A processing apparatus for use in the processing of transverse fish body sections includes a support frame and a video camera for providing a video image of a transverse fish body section to be processed when aimed at the fish body section along a preselected line of sight. A fish section support is provided for supporting the transverse fish section substantially over its area. The support can be invisible on the video photo image and preferably includes a plurality of spaced apart beams which are of a small dimensional width so that they do not appear on the video photo image that contains the fish body sections. A fluid jetting knife is movable with respect to the transverse fish body section for cutting the section with a pressurized fluid stream and positioned to traverse both the fish section and the support means during the cutting operation.