yeah, bullkllr I'd imagine if you started with an empty river and tried to just let it happen naturally it would take a while. You'd have to have neighboring rivers with enough of a population that you could get at least one buck and one hen to stray into the empty river and successfully spawn. Then the smolt need to survive and return. Additionally, you would want more strays to occasionally spawn from time to time so that inbreeding doesn't leave them all susceptible to something like a disease that would wipe them all out. The time from egg to return to spawn varies, but I think Chambers fish are like 4-5 years (2 in rearing ponds then some go to sea for 2-3 years, some hang out in the river for a year then go to sea for a couple years). wild fish seem to add a year or two at sea. So, to get returns built up just from strays, probably be a few fish generations. If there were resident rainbows that might help speed things up a little--you would only need one stray hen. (I think the steelhead hen with the male resident bow is usually how the mixing works best.)