[env-trinity] Trinity River Spawn Survey Update for November 18 to 22

Chamberlain, Charles charles_chamberlain at fws.gov
Sat Nov 23 15:01:07 PST 2013

Hi all,
There's no IT staff available to post the complete report on our website
this week, but I'll do my best to keep you abreast of the latest from our
survey anyway....

Our crews mapped the locations of 490 mainstem redds and 622 carcasses
November 18 to 22.  Counts would have been slightly higher but for poor GPS
coverage for a couple of days. We'll catch up to those un-mapped redds next

This year's Chinook Salmon spawn has not turned out to be a great one,
evident from the graph below.  Our folks are still seeing numbers of fish
out there staging to spawn, but many of those appear to be Coho Salmon.

[image: Inline image 1]

*Fun fact for the week...*
Did you know …. The date a fish emerges from its gravel nest can be roughly
predicted using the date its parents spawned, and the water temperature
history the fish experiences while it develops within the gravel.  Even
after a salmon hatches from its egg it stays within the gravels as an
alevin<http://www.merriam-webster.com/dictionary/alevin>for some time
living on energy reserves stored in the remaining yolk.  Cold
water slows metabolism and the rate at which the fish burns through its
yolk; warm water increases the burn rate (to a point).  When the alevin has
used up its yolk it graduates to ‘fry’ and must emerge from the gravel to a
free-swimming world of predators and competition for habitat and food
resources.  A common metric used to estimate emergence date is Accumulated
Thermal Units or ATU.  To calculate ATU, we begin from the day an egg is
deposited in the gravel by adding the average water temperature in degrees
Celsius from each day.  Chinook Salmon tend to hatch from the egg at around
476 ATU and emerge from the gravel at around 724 ATU (Beacham and Murray
1990).  Coho Salmon develop a bit quicker and, hatch at about 250 ATU, and
emerge at about 344 ATU.  Using the 2012/2013 temperature history from
Steelbridge on the Trinity River, a Chinook Salmon conceived in the
relatively warm waters of late-September would be expected to emerge in
about 82 days.  A Chinook Salmon conceived at the same location in the cool
waters of mid-November might take 113 days to emerge.

I hope you all get to enjoy a great Thanksgiving!
See you next week,

Charles Chamberlain
Supervisory Fish Biologist
U.S. Fish and Wildlife Service
Arcata Fish & Wildlife Office
1655 Heindon Road
Arcata, CA 95521

Charles_Chamberlain at fws.gov
Phone: (707) 825-5110    Fax: (707) 822-8411
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