The World’s Northernmost Harbour Seal Population–How Many Are There?
This study presents the first abundance estimate for the world’s northernmost harbour seal (Phoca vitulina) population, which resides in Svalbard, Norway, based on three digital stereoscopic photographic surveys conducted in 2009 and 2010. The counts from these high resolution 3D images were combine...
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ftrepec:oai:RePEc:plo:pone00:0067576 2024-04-14T08:12:46+00:00 The World’s Northernmost Harbour Seal Population–How Many Are There? Benjamin Merkel Christian Lydersen Nigel G Yoccoz Kit M Kovacs https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067576 https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0067576&type=printable unknown https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067576 https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0067576&type=printable article ftrepec 2024-03-19T10:31:22Z This study presents the first abundance estimate for the world’s northernmost harbour seal (Phoca vitulina) population, which resides in Svalbard, Norway, based on three digital stereoscopic photographic surveys conducted in 2009 and 2010. The counts from these high resolution 3D images were combined with a novel method for estimating correction factors for animals that were in the water at the time of the surveys, in which extensive behavioural data from radio-tagged harbour seals were used together with age distribution data to estimate the proportion of seals of various age and sex classes hauled out at the times of the surveys. To detect possible seasonal shifts in age distribution between surveys, lengths of hauled out seals were measured from the stereoscopic images. No body-length differences were detected between the surveys; but, this may be due to a high degree of sexual dimorphism exhibited in this population. Applying the modelled correction factors, a total of 1888 (95% CI: 1660–3023), 1742 (1381–3549) and 1812 (1656–4418) harbour seals were estimated for the surveys flown on 01 August 2009, 01 August 2010 and 19 August 2010, respectively. The similarity between the three survey estimates (despite significant differences in the number of animals actually counted on the photos from each survey effort) suggests that the variation in numbers of hauled out seals is reasonably accurately adjusted for by the haul-out probability model. The low population size, the limited spatial distribution of the population and its reduced genetic diversity make this population vulnerable to chance events, such as disease epidemics. Article in Journal/Newspaper harbour seal Phoca vitulina Svalbard RePEc (Research Papers in Economics) Svalbard Norway |
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description |
This study presents the first abundance estimate for the world’s northernmost harbour seal (Phoca vitulina) population, which resides in Svalbard, Norway, based on three digital stereoscopic photographic surveys conducted in 2009 and 2010. The counts from these high resolution 3D images were combined with a novel method for estimating correction factors for animals that were in the water at the time of the surveys, in which extensive behavioural data from radio-tagged harbour seals were used together with age distribution data to estimate the proportion of seals of various age and sex classes hauled out at the times of the surveys. To detect possible seasonal shifts in age distribution between surveys, lengths of hauled out seals were measured from the stereoscopic images. No body-length differences were detected between the surveys; but, this may be due to a high degree of sexual dimorphism exhibited in this population. Applying the modelled correction factors, a total of 1888 (95% CI: 1660–3023), 1742 (1381–3549) and 1812 (1656–4418) harbour seals were estimated for the surveys flown on 01 August 2009, 01 August 2010 and 19 August 2010, respectively. The similarity between the three survey estimates (despite significant differences in the number of animals actually counted on the photos from each survey effort) suggests that the variation in numbers of hauled out seals is reasonably accurately adjusted for by the haul-out probability model. The low population size, the limited spatial distribution of the population and its reduced genetic diversity make this population vulnerable to chance events, such as disease epidemics. |
format |
Article in Journal/Newspaper |
author |
Benjamin Merkel Christian Lydersen Nigel G Yoccoz Kit M Kovacs |
spellingShingle |
Benjamin Merkel Christian Lydersen Nigel G Yoccoz Kit M Kovacs The World’s Northernmost Harbour Seal Population–How Many Are There? |
author_facet |
Benjamin Merkel Christian Lydersen Nigel G Yoccoz Kit M Kovacs |
author_sort |
Benjamin Merkel |
title |
The World’s Northernmost Harbour Seal Population–How Many Are There? |
title_short |
The World’s Northernmost Harbour Seal Population–How Many Are There? |
title_full |
The World’s Northernmost Harbour Seal Population–How Many Are There? |
title_fullStr |
The World’s Northernmost Harbour Seal Population–How Many Are There? |
title_full_unstemmed |
The World’s Northernmost Harbour Seal Population–How Many Are There? |
title_sort |
world’s northernmost harbour seal population–how many are there? |
url |
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067576 https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0067576&type=printable |
geographic |
Svalbard Norway |
geographic_facet |
Svalbard Norway |
genre |
harbour seal Phoca vitulina Svalbard |
genre_facet |
harbour seal Phoca vitulina Svalbard |
op_relation |
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067576 https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0067576&type=printable |
_version_ |
1796310615953768448 |