scrape and freeze is always a good option with any skin. You say you want to "process" them, but what are you going to do with them? Bow backing or leather goods or what? One way to produce useable leather from fish is bark tanning- the guy Yosemitie Ben mentioned is great at this technique. Basically, you scrape and descale, then soak in cool tannin solution. when dry, it's a stiff, but useable leather. For Bow backing, you don't tan it, just use it like "rawhide".