[MARMAM] New article: Behavioral observations and stable isotopes reveal high individual variation and little seasonal variation in sea otter diets in Southeast Alaska

Nicole Laroche nlaroche at alaska.edu
Thu Oct 28 10:32:16 PDT 2021


Dear Colleagues,

On behalf of myself and my co-authors, we are excited to share the
following paper:

Behavioral observations and stable isotopes reveal high individual
variation and little seasonal variation in sea otter diets in Southeast
Alaska

Nicole LaRoche, Sydney King, Matthew Rogers, Ginny Eckert, and Heidi Pearson

ABSTRACT
Two complementary approaches were used to assess year-round variation in
the diet of sea otters Enhydra lutris around Prince of Wales Island (POW)
in southern Southeast Alaska, a region characterized by mixed-bottom
habitat. We observed sea otters foraging to determine diet composition
during the spring and summer. Then, we obtained sea otter vibrissae, which
record temporal foraging patterns as they grow, from subsistence hunters to
identify year-round changes in sea otter diets via stable isotope analysis
of carbon (δ13C) and nitrogen (δ15N). We compared the stable isotopes from
sea otter vibrissae and sea otter prey items that were collected during
spring, summer, and winter. Overall, year-round sea otter diet estimates
from stable isotope signatures and visual observations from spring and
summer were dominated by clams in terms of biomass, with butter clams
Saxidomus gigantea the most common clam species seen during visual
observations. Our results indicate that these sea otters, when considered
together at a regional level around POW, do not exhibit shifts in the main
prey source by season or location. However, sea otter diets identified by
stable isotopes had a strong individual-level variation. Behavioral
variation among individual sea otters may be a primary driving factor in
diet composition. This study provides quantitative diet composition data
for modeling predictions of invertebrate population estimates that may aid
in the future management of shellfisheries and subsistence hunting and the
development of co-management strategies for this protected species.

Marine Ecology Progress Series 677:219-232.
https://doi.org/10.3354/meps13871


If you have any questions, please feel free to email: nlaroche at alaska.edu

Best,
Nicole LaRoche
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