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Marine Ecology Progress Series

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MEPS 527:261-274 (2015)  -  DOI:

Stable isotope values in pup vibrissae reveal geographic variation in diets of gestating Steller sea lions Eumetopias jubatus

Rick D. Scherer1,8, Andrew C. Doll1,*, Lorrie D. Rea2,3, Aaron M. Christ2, Craig A. Stricker4, Briana Witteveen5, Thomas C. Kline6, Carolyn M. Kurle7, Michael B. Wunder1

1Department of Integrative Biology, University of Colorado Denver, Denver, CO 80204, USA
2Alaska Department of Fish and Game, Division of Wildlife Conservation, Anchorage, AK 99518, USA
3Institute of Northern Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
4US Geological Survey, Fort Collins Science Center, Denver, CO 80225, USA
5Kodiak Seafood and Marine Science Center, University of Alaska Fairbanks, Kodiak, AK 99615, USA
6Prince William Sound Science Center, Cordova, AK 99574, USA
7Division of Biological Sciences, Ecology, Evolution, and Behavior Section, University of California San Diego, La Jolla, CA 92093, USA
8Present address: Conservation Science Partners, Fort Collins, CO 80524, USA
*Corresponding author:

ABSTRACT: Multiple factors, including limitation in food resources, have been proposed as possible causes for the lack of recovery of the endangered western segment of the Steller sea lion population in the United States. Because maternal body condition has important consequences on fetal development and neonatal survival, the diets of pregnant females may be particularly important in regulating population sizes. We used the stable carbon and nitrogen isotope values of vibrissae from Steller sea lion pups as an indirect indicator of maternal diets during gestation. Combining these data with isotope data from potential prey species in a Bayesian mixing model, we generated proportional estimates of dietary consumption for key prey. Our analysis indicated that females in the most westerly metapopulations relied heavily on Atka mackerel and squid, whereas females inhabiting the Gulf of Alaska region had a fairly mixed diet, and the metapopulation of Southeast Alaska showed a strong reliance on forage fish. These results are similar to previous data from scat collections; however, they indicate a possible under-representation of soft-bodied prey (squid) or prey with fragile skeletons (forage fish) from analyses of data from scats. This study supports the utility of stable isotope modeling in predicting diet composition in gestating adult female Steller sea lions during winter, using pup vibrissae.

KEY WORDS: Stable isotopes · Vibrissae · Steller sea lion · Carbon · Nitrogen · Mixing model · Diet composition

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Cite this article as: Scherer RD, Doll AC, Rea LD, Christ AM and others (2015) Stable isotope values in pup vibrissae reveal geographic variation in diets of gestating Steller sea lions Eumetopias jubatus. Mar Ecol Prog Ser 527:261-274.

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