[env-trinity] Willow Creek Juvenile Salmonid Outmigrant Monitoring In-Season Update

[Bill_Pinnix at fws.gov]

Willow Creek Downstream Migrant Trap Site
                2008 In-Season Trapping Update –July 16, 2008

   Synopsis: The 2008 Downstream Migrant trapping season at the Willow
   Creek Trap Site (river kilometer 34) is being conducted jointly by the
   USFWS Arcata Fish and Wildlife Office (AFWO) and the Yurok Tribal
   Fisheries Program (YTFP) on the mainstem Trinity River near Willow
   Creek, California.  The season began March 13, 2008 with the
   installation of one trap.  A second trap was installed March 15, 2008,
   and a third trap was installed March 27, 2008. See attached catch
   summary for details of this narrative.

   This summary includes data from March 13th, 2008 through July 9th, 2008
   and is presented as raw catch.  No expansions have been calculated at
   this time. Data entry is not complete for Julian Week 28, July 9th  to
   July 15th.  Heavy debris load from floating algae have occasionally
   resulted in null sets, causing less than 21 trap days (3 traps x 7 days)
   in some weeks.  In addition, the traps were not fished a couple of days
   due to heavy smoke and unhealthy conditions for trap crews.

   Raw daily catches of Chinook salmon (Oncorhynchus tshawytscha) have been
   captured each day sampling has occurred and most have been
   young-of-the-year (YOY), with a few age 1+ natural Chinook salmon.
   Weekly mean Fulton’s K values of YOY Chinook salmon began the season
   lower than 1.0 with an increase in condition to greater than 1.0 in
   Julian Week 16 which has stayed relatively stable through Julian Week
   28.  Efficiency calibrations at flow benches were conducted May 8th
   (~10,500 cfs measured at Hoopa Gauge; initial efficiency estimate of
   0.93 %), May 16th (~10,000 cfs; initial efficiency estimate of 1.02 %),
   May 29th (~5,800 cfs; initial efficiency estimate of 3.7%), and June 5th
   (~2,500 cfs; initial efficiency estimate of 3.8%). Natural Chinook
   salmon catches show bi-modal peaks (mid-April, and mid-June) in raw
   catch, both of which are coincident with a dropping of flow; this is
   consistent with past year’s catches.

   Raw daily catches of steelhead (Oncorhynchus mykiss) smolts (age 1+)
   have been dropping off since the beginning of June.  Steelhead smolts
   captured JW 11-23 had weekly mean Fulton’s K values slightly higher than
   1.0, with a steady drop over time (indicating that the smolting process
   is underway).  Steelhead YOY numbers have increased in the catch, and
   have yet to show signs of a peak.

   Raw daily catches of coho salmon (Oncorhynchus kisutch) are low compared
   to the past 5 years, especially for natural smolts.  Weekly mean
   Fulton’s K value of natural coho salmon smolts were higher than 1.0 at
   the beginning of the season and have steadily dropped over time,
   indicating that the smolting process is underway.  A peak in hatchery
   coho smolt catch occurred coincident with the high dam releases in early
   to mid May; this is consistent with past year’s catches. The peak in
   natural coho smolt catch occurred during Julian week 24 during the down
   ramp of flow; this is not consistent with past year’s catches.

   If you have any questions regarding this summary, don't hesitate to
   contact Bill Pinnix at (707) 822-7201.

   (See attached file: WCT_CatchSummary_7_16_08.pdf)


William Pinnix
USFWS, AFWO
1655 Heindon Rd
Arcata, CA 95521
(707) 822-7201
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