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Marine Ecology Progress Series

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MEPS 628:223-234 (2019)  -  DOI:

Identifying foraging habitats of adult female long-nosed fur seal Arctocephalus forsteri based on vibrissa stable isotopes

Dahlia Foo1,*, Mark Hindell1, Clive McMahon2, Simon Goldsworthy3

1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7004, Australia
2Sydney Institute of Marine Science, Mosman, New South Wales 2088, Australia
3Aquatic Sciences Centre, South Australian Research and Development Institute, West Beach, South Australia 5024, Australia
*Corresponding author:

ABSTRACT: We investigated how foraging ecotypes of female long-nosed fur seals Arctocephalus forsteri could be identified from vibrissa stable isotopes. We collected regrowths of vibrissae from adult females (n = 18) from Cape Gantheaume, Kangaroo Island, South Australia, from 2 breeding seasons (2016, 2017). The period represented by the regrowth was known, and 8 individuals were administered with 15N-enriched glycine as a biomarker to mark the start date of the regrowth. Non-glycine-marked and glycine-marked vibrissae were used to estimate the rate of the individual vibrissa regrowth. Using individual growth rates (0.18 ± 0.04 mm d-1), we reconstructed a stable isotope (δ13C and δ15N) time series for each regrowth and allocated them to corresponding at-sea locations either based on geolocation tracks (n = 14) or foraging habitat type (shelf or oceanic) based on diving data (n = 2) of the sampled seals. Mean (±SD) δ15N from vibrissa segments was higher when females foraged on the continental shelf region (16.1 ± 0.7‰, n = 29) compared to oceanic waters (15.1 ± 0.7‰, n = 106) in 2017, whereas it was similar in both regions in 2016 (shelf: 15.3 ± 0.4‰, n = 13; oceanic: 15.4 ± 0.4‰, n = 15). Based on the stable isotope signatures of vibrissa segments, model-based clustering analysis correctly classified 79.8% as originating from shelf or oceanic foraging habitats. This demonstrates the potential of using vibrissa stable isotopes for studying the foraging ecology of an important top marine predator.

KEY WORDS: Isoscape · Foraging strategies · Trophic dynamics · Continental shelf · Oceanic · Marine top predators

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Cite this article as: Foo D, Hindell M, McMahon C, Goldsworthy S (2019) Identifying foraging habitats of adult female long-nosed fur seal Arctocephalus forsteri based on vibrissa stable isotopes. Mar Ecol Prog Ser 628:223-234.

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