[MARMAM] New Publication: Diets of walruses in Bristol Bay, Alaska

John Maniscalco johnm at alaskasealife.org
Fri Mar 20 10:12:57 PDT 2020


Dear Colleagues,

My co-authors and I are pleased to announce the publication of
"Contemporary diets of walruses in Bristol Bay, Alaska suggest temporal
variability in benthic community structure."  Available at PeerJ:
https://peerj.com/articles/8735/

ABSTRACT

*Background.* Pacific walruses (*Odobenus rosmarus divergens*) are a
conspicuous and
important component of the Bristol Bay ecosystem and human social systems,
but very
little is known about walrus ecology in this region, principally their
feeding ecology.
The present work provides contemporary data on the diets of walruses at
four haulout
locations throughout Bristol Bay between 2014 and 2018.

*Methods.* We analyzed scat and gastrointestinal tract samples from these
animals using
quantitative polymerase chain reaction to amplify prey DNA, which allowed
for diet
estimates based on frequencies of prey item occurrence and on the relative
importance
of dietary items as determined from DNA threshold cycle scores.

*Results.* Diets were highly diverse at all locations, but with some
variation in com-
position that may be related to the time of year that samples were
collected (summer
vs. autumn), or to spatial variability in the distribution of prey.
Overall, polychaetes
and tunicates had the highest frequencies of occurrence and relative
abundances in
2014-15, but a major change in diet appears to have occurred by 2017-18.
While some
sample sizes were small, diets in these later years contrasted sharply,
with a greater
prevalence of sea cucumbers and mollusks, and reduced importance of
decapods and
fishes compared to the earlier years. Prey identified in scat samples from
one collection
site also contrasted sharply with those reported from the same location in
1981. The
apparent temporal shifts in walrus prey may represent a changing benthic
ecosystem
due to warming waters in recent decades.

-- 
*John M. Maniscalco, Ph.D., Capt.*
Senior Research Scientist, Alaska SeaLife Center
Owner/Operator, Alaska Seabird Charters
www.alaskaseabirds.com
PO Box 1675
Seward, AK 99664

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*John M. Maniscalco, Ph.D., Capt.*
*Research Scientist*
Alaska SeaLife Center
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