Having had the pleasure of working on some creeks where were marked all the smolts and captured all the adults that went back upstream we learned a lot about wild fish straying. They do, a lot.

With steelhead, about 1/3 of the adults had been marked as smolts. Now, some of the other 2/3 did come from downstream of the rack (1 mile of a 7.5 mile anadromous zone) they all didn't come from there. Plus, we marked all the kelts with numbered tags. Got a goodly number of repeats annually and NONE had been marked. We did get one marked recovery in the Union River and one in the Nisqually.

As to coho, we got better levels of return but still straying. One year, all the adults that had been marked in Salmon Creek returned to Snow. I know they are close, bit ALL?? And, Salmon got a decent unmarked eascapement.

We really don't know how much the wild fish stay because we don't mark and recover them with the same effort we give hatchery fish; it's easier to mark them. And, we don't have intensive recovery efforts.