Journal
MARINE ECOLOGY PROGRESS SERIES
Volume 523, Issue -, Pages 255-266Publisher
INTER-RESEARCH
DOI: 10.3354/meps11205
Keywords
Pinniped; Stable isotopes; Fractionation; Diet; Vibrissae
Categories
Funding
- NOAA to the Alaska SeaLife Center
- National Marine Mammal Laboratory
- North Pacific Wildlife Consulting
- Marine Mammal Energetics Aquarium
- North Pacific Marine Science Foundation
- NOAA
- Animal Care Permits from the University of British Columbia
- NOAA Cooperative Agreements
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Nutritional constraints have been proposed as a contributor to population declines in the endangered Steller sea lion Eumetopias jubatus in some regions of the North Pacific. Isotopic analysis of vibrissae (whiskers) is a potentially useful approach to resolving the nutritional ecology of this species because long-term (up to 8 yr) dietary information is sequentially recorded and metabolically inert once formed. Additionally, vibrissae are grown in utero, potentially offering indirect inference on maternal diet. However, diet reconstruction using isotopic techniques requires a priori knowledge of trophic enrichment factors (TEFs), which can vary relative to diet quality and among animal species. In this study, we provide new TEF estimates for (1) maternal relative to pup vibrissae during both gestation and nursing and (2) adult vibrissae relative to a complex diet. Further, we refine vibrissa-milk TEFs based on an additional 76 animals with an age distribution ranging from 1 to 20 mo. Mother-pup vibrissae TEF values during gestation and nursing were near zero for delta C-13 and averaged 0.8 and 1.6%, respectively, for delta N-15. In contrast, vibrissa-fish/invertebrate TEFs averaged 3.3 (+/- 0.3 SD) and 3.7% (+/- 0.3) for lipid-free delta C-13 and delta N-15, respectively. Average lipid-free d(13)C and d(15)N vibrissa-milk TEFs were 2.5 (+/- 0.9) and 1.8% (+/- 0.8), respectively, and did not differ among metapopulations. Empirically determined TEFs are critical for accurate retrospective diet modeling, particularly for evaluating the hypothesis of nutritional deficiency contributing to the lack of Steller sea lion population recovery in some regions of Alaska.
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