Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)

Abstract We analyzed and compared trends in age-at-maturity and body growth in the Greenland Sea and Barents Sea stocks of harp seals, Pagophilus groenlandicus, from the early 1960s to the early 1990s. Mean and median age at sexual maturity (MAMPM and MdAM) were estimated from Richards curves fit to...

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Published in:ICES Journal of Marine Science
Main Authors: Kirstine Frie, Anne, Potelov, Vladimir A, Kingsley, Michael C.S, Haug, Tore
Format: Article in Journal/Newspaper
Language:English
Published: Oxford University Press (OUP) 2003
Subjects:
Online Access:http://dx.doi.org/10.1016/s1054-3139(03)00123-1
http://academic.oup.com/icesjms/article-pdf/60/5/1018/29119234/60-5-1018.pdf
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spelling croxfordunivpr:10.1016/s1054-3139(03)00123-1 2024-09-15T17:57:42+00:00 Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777) Kirstine Frie, Anne Potelov, Vladimir A Kingsley, Michael C.S Haug, Tore 2003 http://dx.doi.org/10.1016/s1054-3139(03)00123-1 http://academic.oup.com/icesjms/article-pdf/60/5/1018/29119234/60-5-1018.pdf en eng Oxford University Press (OUP) ICES Journal of Marine Science volume 60, issue 5, page 1018-1032 ISSN 1095-9289 1054-3139 journal-article 2003 croxfordunivpr https://doi.org/10.1016/s1054-3139(03)00123-1 2024-07-08T04:25:42Z Abstract We analyzed and compared trends in age-at-maturity and body growth in the Greenland Sea and Barents Sea stocks of harp seals, Pagophilus groenlandicus, from the early 1960s to the early 1990s. Mean and median age at sexual maturity (MAMPM and MdAM) were estimated from Richards curves fit to age-specific proportions mature. No long-term trends were found in the Greenland Sea seals, where a common value of MAMPM (5.6 years) and MdAM (4.8 years) could be fit to samples from 1959 through 1990. There were also no significant changes in length-at-age of molting females between 1964 and 1987. For Barents Sea harp seals, MAMPM increased significantly from 5.4 years in the period 1962–1972 to 6.6 years in 1976–1985 and 8.2 years in 1988–1993, concurrently with a decline in body growth rates. Tests on MdAM also showed an increasing trend, but the grouping of samples was slightly different. Estimates of MAMPM for the Barents Sea stock were similar to previously published back-calculated values of MAM, but simulations showed that this method is sensitive to the age distribution of the sample, thus complicating comparisons between samples with different age structures. The high values of MAMPM and low growth rates in the Barents Sea stock in the late 1980s to early 1990s coincided with severe depletion of important prey species in the Barents Sea, reports of mass invasions of harp seals along the Norwegian coast and indications of reduced body condition. All these are consistent with a hypothesis of reduced per-capita resource levels within the distribution area of Barents Sea harp seals at that time, but no cause-and-effect relationship for the long-term trend in age-at-maturity can be established. Article in Journal/Newspaper Barents Sea Greenland Greenland Sea Northeast Atlantic Pagophilus groenlandicus Oxford University Press ICES Journal of Marine Science 60 5 1018 1032
institution Open Polar
collection Oxford University Press
op_collection_id croxfordunivpr
language English
description Abstract We analyzed and compared trends in age-at-maturity and body growth in the Greenland Sea and Barents Sea stocks of harp seals, Pagophilus groenlandicus, from the early 1960s to the early 1990s. Mean and median age at sexual maturity (MAMPM and MdAM) were estimated from Richards curves fit to age-specific proportions mature. No long-term trends were found in the Greenland Sea seals, where a common value of MAMPM (5.6 years) and MdAM (4.8 years) could be fit to samples from 1959 through 1990. There were also no significant changes in length-at-age of molting females between 1964 and 1987. For Barents Sea harp seals, MAMPM increased significantly from 5.4 years in the period 1962–1972 to 6.6 years in 1976–1985 and 8.2 years in 1988–1993, concurrently with a decline in body growth rates. Tests on MdAM also showed an increasing trend, but the grouping of samples was slightly different. Estimates of MAMPM for the Barents Sea stock were similar to previously published back-calculated values of MAM, but simulations showed that this method is sensitive to the age distribution of the sample, thus complicating comparisons between samples with different age structures. The high values of MAMPM and low growth rates in the Barents Sea stock in the late 1980s to early 1990s coincided with severe depletion of important prey species in the Barents Sea, reports of mass invasions of harp seals along the Norwegian coast and indications of reduced body condition. All these are consistent with a hypothesis of reduced per-capita resource levels within the distribution area of Barents Sea harp seals at that time, but no cause-and-effect relationship for the long-term trend in age-at-maturity can be established.
format Article in Journal/Newspaper
author Kirstine Frie, Anne
Potelov, Vladimir A
Kingsley, Michael C.S
Haug, Tore
spellingShingle Kirstine Frie, Anne
Potelov, Vladimir A
Kingsley, Michael C.S
Haug, Tore
Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)
author_facet Kirstine Frie, Anne
Potelov, Vladimir A
Kingsley, Michael C.S
Haug, Tore
author_sort Kirstine Frie, Anne
title Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)
title_short Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)
title_full Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)
title_fullStr Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)
title_full_unstemmed Trends in age-at-maturity and growth parameters of female Northeast Atlantic harp seals, Pagophilus groenlandicus (Erxleben, 1777)
title_sort trends in age-at-maturity and growth parameters of female northeast atlantic harp seals, pagophilus groenlandicus (erxleben, 1777)
publisher Oxford University Press (OUP)
publishDate 2003
url http://dx.doi.org/10.1016/s1054-3139(03)00123-1
http://academic.oup.com/icesjms/article-pdf/60/5/1018/29119234/60-5-1018.pdf
genre Barents Sea
Greenland
Greenland Sea
Northeast Atlantic
Pagophilus groenlandicus
genre_facet Barents Sea
Greenland
Greenland Sea
Northeast Atlantic
Pagophilus groenlandicus
op_source ICES Journal of Marine Science
volume 60, issue 5, page 1018-1032
ISSN 1095-9289 1054-3139
op_doi https://doi.org/10.1016/s1054-3139(03)00123-1
container_title ICES Journal of Marine Science
container_volume 60
container_issue 5
container_start_page 1018
op_container_end_page 1032
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