Steelhead have a high incidence of straying, both wild fish and hatchery fish. It's a survival mechanism, to spread the gene pool far and wide to colonize new habitat and/or prevent natural occurences (floods, volcanoes, blocking slides, etc.) from eliminating the genetic characteristics of that particular run. Good example was when St. Helens blew, most of the fish from the Toutle went up the Kalama instead. When you get a tag like tat, you're supposed to contact the nearest WDFW office.