[env-trinity] Willow Creek Juvenile Salmonid Outmigrant Monitoring In-Season Update
Bill_Pinnix at fws.gov
Wed Jul 16 10:54:04 PDT 2008
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)
1655 Heindon Rd
Arcata, CA 95521
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