Rates of increase in age-structured populations: a lesson from the European harbour seals
Behavioural differences among population segments coupled with the transient dynamics of perturbed population structures lead to severely biased estimates of the intrinsic rates of increase in natural populations. This phenomenon is expected to occur in most populations that are structured by age, s...
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Online Access: | http://dx.doi.org/10.1139/z02-141 http://www.nrcresearchpress.com/doi/pdf/10.1139/z02-141 |
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crcansciencepubl:10.1139/z02-141 2024-09-30T14:41:21+00:00 Rates of increase in age-structured populations: a lesson from the European harbour seals Härkönen, Tero Harding, Karin C Heide-Jørgensen, Mads-Peter 2002 http://dx.doi.org/10.1139/z02-141 http://www.nrcresearchpress.com/doi/pdf/10.1139/z02-141 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Zoology volume 80, issue 9, page 1498-1510 ISSN 0008-4301 1480-3283 journal-article 2002 crcansciencepubl https://doi.org/10.1139/z02-141 2024-09-19T04:09:49Z Behavioural differences among population segments coupled with the transient dynamics of perturbed population structures lead to severely biased estimates of the intrinsic rates of increase in natural populations. This phenomenon is expected to occur in most populations that are structured by age, sex, state, or rank. The 1988 epizootic in European harbour seals (Phoca vitulina) perturbed the population composition radically. Detailed documentation of mass mortality, 20 years of population surveys, and data on age- and sex-specific behaviour were used to quantify biases in the observed rate of increase (λ obs. ), which in many areas substantially exceeded the "maximum rate of increase". This is serious, since λ obs. is a key parameter, for example, in estimating potential biological removal or modelling population dynamics. For populations where the underlying age and sex composition is unknown, we suggest that data on fecundity and survival rates be used to find the upper theoretical rate of population increase. We found that the intrinsic rates of increase (λ 1 ) in populations of true seals with even sex ratios and stable age structures cannot exceed 13% per year (λ 1max. = 1.13). Frequently reported larger values are indicative of nonstable population structures or populations affected by migrations. Article in Journal/Newspaper Phoca vitulina Canadian Science Publishing Canadian Journal of Zoology 80 9 1498 1510 |
institution |
Open Polar |
collection |
Canadian Science Publishing |
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crcansciencepubl |
language |
English |
description |
Behavioural differences among population segments coupled with the transient dynamics of perturbed population structures lead to severely biased estimates of the intrinsic rates of increase in natural populations. This phenomenon is expected to occur in most populations that are structured by age, sex, state, or rank. The 1988 epizootic in European harbour seals (Phoca vitulina) perturbed the population composition radically. Detailed documentation of mass mortality, 20 years of population surveys, and data on age- and sex-specific behaviour were used to quantify biases in the observed rate of increase (λ obs. ), which in many areas substantially exceeded the "maximum rate of increase". This is serious, since λ obs. is a key parameter, for example, in estimating potential biological removal or modelling population dynamics. For populations where the underlying age and sex composition is unknown, we suggest that data on fecundity and survival rates be used to find the upper theoretical rate of population increase. We found that the intrinsic rates of increase (λ 1 ) in populations of true seals with even sex ratios and stable age structures cannot exceed 13% per year (λ 1max. = 1.13). Frequently reported larger values are indicative of nonstable population structures or populations affected by migrations. |
format |
Article in Journal/Newspaper |
author |
Härkönen, Tero Harding, Karin C Heide-Jørgensen, Mads-Peter |
spellingShingle |
Härkönen, Tero Harding, Karin C Heide-Jørgensen, Mads-Peter Rates of increase in age-structured populations: a lesson from the European harbour seals |
author_facet |
Härkönen, Tero Harding, Karin C Heide-Jørgensen, Mads-Peter |
author_sort |
Härkönen, Tero |
title |
Rates of increase in age-structured populations: a lesson from the European harbour seals |
title_short |
Rates of increase in age-structured populations: a lesson from the European harbour seals |
title_full |
Rates of increase in age-structured populations: a lesson from the European harbour seals |
title_fullStr |
Rates of increase in age-structured populations: a lesson from the European harbour seals |
title_full_unstemmed |
Rates of increase in age-structured populations: a lesson from the European harbour seals |
title_sort |
rates of increase in age-structured populations: a lesson from the european harbour seals |
publisher |
Canadian Science Publishing |
publishDate |
2002 |
url |
http://dx.doi.org/10.1139/z02-141 http://www.nrcresearchpress.com/doi/pdf/10.1139/z02-141 |
genre |
Phoca vitulina |
genre_facet |
Phoca vitulina |
op_source |
Canadian Journal of Zoology volume 80, issue 9, page 1498-1510 ISSN 0008-4301 1480-3283 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/z02-141 |
container_title |
Canadian Journal of Zoology |
container_volume |
80 |
container_issue |
9 |
container_start_page |
1498 |
op_container_end_page |
1510 |
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1811643752281800704 |