Abstract
ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 37:255-267 (2018) - DOI: https://doi.org/10.3354/esr00925 Population viability analysis of Guadalupe fur seals Arctocephalus townsendi Claudia J. Hernández-Camacho1,*, Andrew W. Trites2 1Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional, 23096 La Paz, Baja California Sur, México 2Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada *Corresponding author: cjhernandez78@gmail.com ABSTRACT: The Guadalupe fur seal Arctocephalus townsendi was intensively hunted and considered extinct by the end of the 1800s. However, small numbers (<20 seals) were reported on Guadalupe Island (Mexico) in the mid-1950s and were observed at a second location (San Benito Islands, Mexico) in the late 1990s. Sporadic counts at these 2 sites have followed a relatively rapid increase in numbers, but considerable uncertainty remains about the long-term viability of this recovering species. We performed a population viability analysis using historic seal counts from Guadalupe Island and the San Benito Islands to predict the probability of each colony (and both colonies combined) going extinct under 3 critical population threshold scenarios (100, 500, and 1000 seals). Using a diffusion approximation model, we found that the growth rates of the 2 colonies were similar (10-11% yr-1) and that the population totaled ~41000 individuals in 2017 (x̄ = 40614, 95% CI = 35779-46877). Guadalupe fur seals appear to be vulnerable to extreme climatic events. Of the 2 fur seal colonies, the San Benito Islands colony is less secure and is Endangered to Critically Endangered, depending on the quasi-extinction value used under the quantitative listing criteria established by the IUCN. In contrast, the Guadalupe Island colony and the 2 colonies combined meet the quantitative analysis criteria of Least Concern. Population viability analysis is an important component of assessing the status of wildlife populations and assisting nations and organizations in assigning appropriate categories of protection. KEY WORDS: Guadalupe fur seal · Population viability analysis · PVA · Probability of extinction · Endangered species · Population trend · Pinnipeds Full text in pdf format PreviousNextCite this article as: Hernández-Camacho CJ, Trites AW (2018) Population viability analysis of Guadalupe fur seals Arctocephalus townsendi. Endang Species Res 37:255-267. https://doi.org/10.3354/esr00925 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 37. Online publication date: December 13, 2018 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2018 Inter-Research.
Highlights
The Guadalupe fur seal Arctocephalus townsendi is endemic to the Pacific Ocean and currently only breeds in Mexico (Aurioles-Gamboa et al 2010)
We developed 3 count-based population viability analysis (PVA) for the Guadalupe fur seal occurring on (1) Guadalupe Island, (2)
Hernández-Camacho & Trites: PVA of Guadalupe fur seals ported on the San Benito Islands
Summary
The Guadalupe fur seal Arctocephalus townsendi is endemic to the Pacific Ocean and currently only breeds in Mexico (Aurioles-Gamboa et al 2010). In 2010, the minimum population size of Guadalupe fur seals during the breeding season was estimated to be 2503 seals at the San Benito Islands and. Unusual numbers of fur seals of different age and sex classes stranded in recent years throughout parts of their former distribution and beyond (i.e. central California, Pacific coast of Mexico, Gulf of California, and Vancouver Island in British Columbia, Canada) (Villegas-Zurita et al 2015, ElorriagaVerplancken et al 2016a, Aurioles-Gamboa et al.2017, Carretta et al 2017). Troublesome are the recent numbers of young seals that have stranded and died along the coasts of California and Baja California, as well as the dead adult and subadult fur seals that have washed ashore (Aurioles-Gamboa et al 2017, Carretta et al 2017). 2012) and estimated the average total population size of Guadalupe fur seals in 2017 using stochastic lambda values (λ)
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