Mike Wagenbach wagen13 at yahoo.com wrote:

> > the colony is a few miles from the mouth of the Puyallup River, and
> > a portion of coho and chinook salmon fry/smolts have been
> > marked with small (1mm) stainless CWTs.

> Hadn't thought of this aspect of salmon tagging. Are the tags harmless
> to animals that eat the smolts

Hi Mike -

These tags are fine gauge stainless steel wire about 1mm in length. They
are placed
in the snout of the fish with a retractable needle, (hopefully) stay in
place for the life
of the fish, and have to be found by someone using an electronic (magnetic)
detector.
The little-bitty wires are etched with a series of coded marks, and visually
read under
a microscope. Kind of an arcane art. I read that some of the new tags are
etched with
regular numbers rather than dots-and-dashes or whatever. The codes are
generally a
'batch code' for a large group of fish (<40,000 to hundreds of thousands of
smolts per
code; if the managers know what hatchery, hatchery pond, feeding regime,
release date,
downstream migrant trap, etc., etc. are associated with each code, the
survival rates of
each treatment group can be determined and compared, as well as the harvest
rates by
sport, tribal or commercial fisheries, etc. Potentially even predation by
terns??)

As the tags are commonly found in guano, I imagine that they shoot through a
tern like
corn through a heifer or a penny through a 3-year-old, and cause no harm to
the birds.
As they say... "this, too, shall pass".

Hope this helps,

Jon. Anderson
Olympia, Washington
festuca at olywa.net