WE HAVE RAIN BUT PROBLEMS STILL EXIST
With the rain everyone has hopes that the drought
thing is all done, gone, bye bye but the effects will linger. Even with the
rain flows will drop down below average again by around the 10th of November
according to the Northwest River Forecast Center. So just when you think your safe this will materialize.
A retired staffer sent this a bit back and it is about to become relevant.
You noted, correctly, that low flows may not let Coho
penetrate as far up the tribs. This means that, for a given spawn, fewer smolts
will be produced. In the extreme drought at Snow, more Coho spawned in half the
stream. We got half the smolts. Second thing that happened, and this will be
critical because they use Index sections to survey, is that there will be more
fish in the indexes because they can't get higher. We saw this, too,
since we surveyed 100% of the anadromous zone. So, the estimated Coho
escapement for 2015 will be reported as a number that is "higher"
than reality and this will lead to a larger forecast in 2018.
As to chum, the method I have seen to estimate
escapement is a mean number of fish days; how long a live fish is in the index.
The number used in PS was around 10. Again, in the drought year, Snow and
Salmon creeks had different survivals with Salmon being less than a week.
The result was that the official escapement for Snow was higher than the
official escapement for Salmon, even though Salmon had about twice as many
spawners. We cut tails off of all carcasses so we only counted them once.
In another drought in the mid-80s, a stream in Hood Canal never had a
single live fish. One week, zero. Next week, post rain, 100 dead. By the
"official" method there was no escapement. Plus, chum will also be
affected by how far upstream they get.
Escapement methodologies are built on averages and
Posted on Sat, October 31, 2015
by Dave Hamilton