[env-trinity] 2007 Willow Creek Downstream Migrant In-Season Trapping Update

Bill_Pinnix@fws.gov Bill_Pinnix at fws.gov
Thu May 31 12:05:24 PDT 2007


To Whom it May Concern:

                  Willow Creek Downstream Migrant Trap Site
                 2007 In-Season Trapping Update –May 31, 2007

   Synopsis: The 2007 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 5, 2007 with the installation
   of one trap.  A second trap was installed March 15, 2007, and a third
   trap was installed April 4th, 2007.

   This summary includes data from March 6th, 2007 through May 31st, 2007
   and is presented as raw catch.  No expansions have been calculated at
   this time. Data entry is not complete for Julian Weeks 21 and 22, May
   21st to June 3rd.  Heavy debris load from the increased dam releases
   created problems for the rotary screw traps during Julian Weeks (JW)
   18–20, and resulted in less than 21 trap days per week (7 days per week
   x 3 traps= 21 trap days per week).  See attached catch summary for
   details of this narrative.

   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 are slightly higher than 1.0 with a possible increase in
   condition from JW 15-22 compared to JW 10-14.  Chinook salmon catches
   decreased coincident with increased flows during JW 18 (accounting for
   fewer trap days) and higher catches in JW 19-20 are consistent with the
   theory that juvenile Chinook salmon ‘hunker down’ during flow increases
   and resume emigration on the descending limb of the hydrograph.

   Raw daily catches of steelhead (Oncorhynchus mykiss) smolts (age 1+)
   peaked coincident with the increased flow in JW 17 and have tapered off
   since; total steelhead smolt catch appears to be around average compared
   to the past 5 years.  No age 2 steelhead occur on the catch summary
   because steelhead scales have not been aged this year; once aging is
   complete some age1 steelhead will be moved to the age 2 column.
   Steelhead smolts captured JW 10-19 had weekly mean Fulton’s K values
   slightly higher than 1.0; values dropped below 1.0 in JW 20-22 possibly
   indicating that the smolting process is occurring.  Steelhead YOY
   catches showed a small pulse in JW 13-15 and appear to be increasing in
   the past few weeks.  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 in
   JW 11-18, but have decreased below 1.0 in JW 19-22; possibly indicating
   that the smolting process is occurring.  Coho salmon smolt catches, both
   natural and hatchery, in JW 17 increased coincident with the increased
   water releases from Lewiston Dam.

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

   (See attached file: WCT_CatchSummary_May_31_2007.pdf)



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