[env-trinity] Trinity River Spawn Survey Update for December 9 to 13

[Chamberlain, Charles]

Hi folks,
Look for post of the complete update on our
website<http://www.fws.gov/arcata/fisheries/default.htm> early
next week.  Until then, here's the latest from our survey....

Our crews mapped the locations of 155 mainstem redds and 854 carcasses
December 9 to 13.

About 88% of the newly encountered carcasses were Coho Salmon.  The
cumulative graph for the season so far looks like this:

[image: Inline image 1]


*Fun fact for the week...*
Did you know ….  In the wild, eggs, alevins and newly emerged fry face a
world of natural mortality pressures from competition, predators, and
physical challenges of the river itself.  A hatchery reduces those
challenges for its population in a controlled environment to help
efficiently meet its production goals.  Survival to adulthood increases
absent those natural forces of mortality and contributes to efficient
production of a fishable hatchery salmon population.  In doing so, those
“unchallenged” salmon return to pass on genetic traits that differ from
their wild counterparts.  An example trait shown to be influenced by the
controlled environment of a hatchery is egg size.  In the wild, large
offspring have significant fitness advantages and survival over small
offspring.  Those advantages exert an evolutionary pressure to production
of large eggs which survive the wild environment in greater proportion than
do small eggs.  Absent that selective pressure for large eggs, the egg size
of hatchery populations over very few generations becomes reduced in favor
of production of smaller but more numerous eggs per individual female.
Such unintentional selection can rapidly influence the fitness of a
naturally spawning population if the interaction between a hatchery and
natural populations is high.  Reducing those interactions on natural
spawning grounds is important for maintaining or improving natural salmon
production.

Reisenbichler and Rubin
1999<http://nativefishsociety.org/conservation/wild_vs_hatchery/annotated_bibliography_on_salmon_hatcheries/fitness/ReisenbichlerRubin.pdf>,
Chilcote 2003<http://nativefishsociety.org/conservation/wild_vs_hatchery/annotated_bibliography_on_salmon_hatcheries/fitness/Chilcote2004Pub%5B1%5D.pdf>,
Heath et al. 2003 <http://www.sciencemag.org/content/299/5613/1738.full>



We will be conducting our last Fall 2013 survey December 16 to 20.  I'll
check in with you once more with a final in-season update next week.
Charlie

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
www.fws.gov/arcata/fisheries
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