I think the Yough issues were touched on a few years back in a thread on here. While many tailwaters have brown trout that don't require feeders to spawn. They'll do it mid river if they can find the right conditions. Between Confluence and Ohiopyle, I can think of 3-4 spots that would be possible spawning area. In that same section, how many tribes flow in this would give fish passage and have the required bottom? I'm not sure there's one. While I don't rule out reproduction, it's minimal at best.
If you could combine the Yough temps / flows with the feeders of the Lehigh..... You'd have a dandy