I haven't been around the Skokomish since the old de-watered days of the North Fork, but I wouldn't be so sure that steelhead could not pass the Staircase Falls. I'm pretty sure that even the FERC licensing documents put together by Tacoma Public Utilities did not call it a complete blockage to all species. If steelhead could pass, I think there is somewhere around 7 miles of spawning and rearing a habitat above it that they could use. (Based on ~ 30 year-old memory, so take that for what it is worth.)