"Wolfgang" wrote in message
...

"Bob Weinberger" wrote in message
news:MYBii.8255$DM4.5582@trndny06...
snip
Meanwhile, and not so incidentally, I've seen indications in recent years
that the salmons' famed fidelity to their natal streams is not so
hard-wired and infallible as was once supposed. I believe the issue, like
so many others (lifelong monogamy in various species comes quickly to
mind) is still pretty controversial, but even the staunchest advocates
(well, at least among those who take their heads out of their asses long
enough to enjoy the novelty of free oxygen) have had to admit at least
that there are occasional and incontrovertible exceptions.
snip
Wolfgang
The tendency for a relatively small % of salmon to stray from returning to
their natal streams to spawn has been known for at least 30 years, maybe
longer. However, of all the studies that I have seen, none ever documented
straying of more than one or two drainages past their natal stream, though
I seem to recall several reports of fish straying into and spawning in
streams that were significantly short of reaching their natal streams.
Fishery Bio's theorize that this, along with the tendency for some salmon to
stay in the ocean for lesser or longer than "normal" periods (e.g. Chinook
may stay anywhere from 1- 5years in the salt), is an adaptation for
repopulating streams that suffer a temporary catastrophe. That's why the
Coho Salmon run on the North Fork of the Toutle river, which was devastated
by the eruption of Mt. St Helens was back to pre-eruption levels within
about 5 years.

Bob Weinberger