[env-trinity] In Season Trapping Update, Juvenile Salmonid Monitoring on the Trinity River at Willow Creek

Bill_Pinnix@fws.gov Bill_Pinnix at fws.gov
Thu Jul 29 14:07:52 PDT 2010

Willow Creek Downstream Migrant Trap Site
                2010 In-Season Trapping Update –July 29, 2010

   Synopsis: The 2010 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 8th, 2010 with the
   installation of two traps.  A third trap was installed March 9th, 2010.
   See attached catch summary for details of this narrative.

   This summary includes data from March 9th, 2010 through July 20 th, 2010
   and is presented as raw catch.  No expansions have been calculated at
   this time.  Heavy debris load and high flows have occasionally resulted
   in null sets, causing less than 21 trap days (3 traps x 7 days) in some
   weeks resulting in variable effort over the season; therefore raw catch
   numbers should be interpreted with caution.

   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).  Weekly mean Fulton’s K values of YOY Chinook
   salmon were greater than 1.0 for all weeks sampled except JW 10 and 11.
   Efficiency calibrations were conducted with freeze-branded hatchery
   Chinook salmon during Julian Weeks 10-28.

   Raw daily catches of steelhead (Oncorhynchus mykiss) smolts (age 1+)
   have been relatively steady since the beginning of trapping with
   hatchery steelhead showing up in JW 12; catch of steelhead smolts
   dropped off beginning mid-June.  Weekly mean Fulton’s K values of
   Steelhead smolts were greater than 1.0 for all weeks sampled except JW
   14 and JW 18-20 and JW 22.  The drop in condition factor in the later
   weeks is consistent with smoltification processes. Steelhead YOY numbers
   have increased in the recent weeks and appear to have peaked, but catch
   is still consistent.

   Raw daily catches of coho salmon (Oncorhynchus kisutch) are lower than
   last year at this time but not significantly lower than other years
   prior.  Weekly mean Fulton’s K value of natural coho salmon smolts has
   varied greatly from week to week due to low catches.  Hatchery Coho
   smolts occurred in the catch beginning Julian Week 15.

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

   (See attached file: WCT_Catch_Summary_07_29_10.pdf)

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