[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 –June 10, 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 June 5th, 2008
   and is presented as raw catch.  No expansions have been calculated at
   this time. Data entry is not complete for Julian Weeks 21 and 23, May
   21st to May 27th, and June 4th to June 10th  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.  This accumulation
   of algae in the rotary screw traps is a relatively new phenomenon for
   the Trinity River, and has necessitated increased trap checks at night
   as well as during the day.

   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 continued through Julian Week 23.  Efficiency
   calibrations at high 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 0.79 %), May 29th
   (~5,800 cfs; initial efficiency estimate of 3.8%), and June 5th (~2,500
   cfs; initial efficiency estimate of 3.7%). Natural Chinook salmon
   catches show bimodal peaks 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 increasing as the season progresses.  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 have begun to increase in the catches, but
   still at low levels.  Normal peaks in YOY steelhead catch occur in
   mid-June to early July.

   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, again
   indicating that the smolting process is underway.  A peak in coho smolt
   catch occurred coincident with the high dam releases in early May, this
   is 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_6_10_08.pdf)


William Pinnix
USFWS, AFWO
1655 Heindon Rd
Arcata, CA 95521
(707) 822-7201
-------------- next part --------------
A non-text attachment was scrubbed...
Name: WCT_CatchSummary_6_10_08.pdf
Type: application/pdf
Size: 29657 bytes
Desc: not available
URL: <http://www2.dcn.org/pipermail/env-trinity/attachments/20080611/2b3afbb0/attachment.pdf>