[env-trinity] Mainstem Trinity River Spawn Survey Update for December 16, 2016

Rupert, Derek derek_rupert at fws.gov
Tue Dec 20 17:22:20 PST 2016

Hello All,

The US Fish and Wildlife Service along with the Yurok Tribe, California
Department of Fish and Wildlife, US Forest Service, and Hoopa Valley Tribe
have another weekly update for our Trinity River mainstem spawn survey.
The full update is posted on the Arcata Fish and Wildlife Fisheries

Trinity River spawn Survey update December 16, 2016.

This week our crews mapped 13 redds (1,631 total for the year) in the
Reaches from Lewiston Dam  to Cedar Flat. The graph below is clipped from
our weekly report (limited to the river upstream of Cedar Flat).

​This is our final update for the 2016 Trinity River salmon spawning
surveys.  This season’s surveys were defined by wet weather and low salmon
abundance.  Starting in October, rain events were common throughout the
survey period.  Frequent rains elevated flows and turbidity in much of the
mainstem, which inhibited many of the scheduled surveys.  Redds were
detected in only 1 of 4 surveys conducted (14 were cancelled) below the
confluence with the South Fork Trinity River, due to high water.  Above the
South Fork confluence (Lewiston Dam to Cedar Flat), where flow peaks were
less severe, our crews located  1,631 salmon redds.  This was the lowest
annual redd count on the Trinity River in the 15-year history of this
survey (see figure above).  Reach 1 (Lewiston Dam to Old Bridge) redd
counts are typically the highest in these surveys (averaging 1,493 redds
annually from 2002 to 2015), but this year only 124 redds were located in
this section of the river.  Carcass counts were also the lowest on record
(since 2002), with 268 fresh spawned female salmon carcasses observed.
Prespawn mortality was only evident in 2 of the 270 (<1%) female salmon
sampled.  Our data are consistent with the low numbers of salmon
encountered at the Trinity River Hatchery and Willow Creek Weir.

Let's all hope Santa brings a bigger salmon run next year.

Derek Rupert
Fish Biologist
US Fish and Wildlife Service
Weaverville, CA
Office 530.623.1805
Cell 570.419.2823
Derek_Rupert at fws.gov
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