Well, almost pure strains of wild steelhead make their way above Dougan Falls on the Washougal River. Natural barriers, in this case a waterfall, seem to act as good obstacles to separate out the inferior hatchery steelhead from the wild steelhead.
Studies have been conducted over the years to chart the passages of hatchery and of wild steelhead in various watersheds. The Washougal River has no man made barriers, only natural barriers in waterfalls.
“On the Washougal, our data indicate that natural passage barriers (waterfalls) effectively isolate returning wild steelhead from straying, hatchery-origin adults. Above Dougan Falls on the Washougal, less than 3% of returning adults have been identified as hatchery origin. Using this data, WDFW determined this area to be a genetic sanctuary…” (Clark-Skamania FF)
The Native Fish Society published a study by Bill McMillan re wild steelhead with references to the Washougal River and Dougan Falls