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Frie AK, Lindström U. Exploring the effects of methodological choices on the estimation and biological interpretation of life history parameters for harbour porpoises in Norway and beyond. PLoS One 2024; 19:e0301427. [PMID: 38968179 PMCID: PMC11226007 DOI: 10.1371/journal.pone.0301427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 03/15/2024] [Indexed: 07/07/2024] Open
Abstract
This study investigates effects of subtle methodological choices on the estimation and biological interpretation of age, growth and reproductive parameters for harbour porpoises. The core analyses are based on a focal Norwegian data set built on samples from 134 harbour porpoises caught incidentally in gillnet fisheries along the Norwegian coast during autumn 2016 and spring 2017. Two contrasting practices for interpretation of seasonal and ontogenetic characteristics of tooth growth layer formation resulted in significant age differences among spring samples of young porpoises and for older animals across seasons. In turn, these differences affected estimates of age at maturity and asymptotic lengths, respectively. We also found significant differences in male age at maturity between two well-documented maturity criteria and between mathematical estimators of age at maturity for both sexes. Two different criteria for corpus albicans classification furthermore resulted in different patterns of ovarian corpora accumulation, which may affect some estimates of fecundity rates and contaminant loads. Both corpora accumulation patterns were also found in reanalysed data from German and Greenlandic porpoises. Based on tabulated overviews of methodological choices made in previous harbour porpoise studies, we argue that several of the issues mentioned above have wider relevance and may affect the validity of meta-analyses as a tool for estimating harbour porpoise sensitivity to extrinsic pressures. Differences in cause of death (COD) composition between data sets can have a similar effect. We demonstrate this in a meta-analysis of published harbour porpoise pregnancy rates, showing significantly higher values for trauma-killed samples compared to samples comprising mixed COD categories. COD also affected the estimated impacts of three previously analysed extrinsic predictors as well as an added predictor for vessel noise levels. We discuss the potential contributions of methodological, biological and anthropogenic factors in shaping observed regional differences in estimates of harbour porpoise life history parameters.
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Affiliation(s)
| | - Ulf Lindström
- Institute of Marine Research, Tromsø, Norway
- UiT The Arctic University of Norway, Tromsø, Norway
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Liu X, Schjøtt SR, Granquist SM, Rosing-Asvid A, Dietz R, Teilmann J, Galatius A, Cammen K, O Corry-Crowe G, Harding K, Härkönen T, Hall A, Carroll EL, Kobayashi Y, Hammill M, Stenson G, Frie AK, Lydersen C, Kovacs KM, Andersen LW, Hoffman JI, Goodman SJ, Vieira FG, Heller R, Moltke I, Tange Olsen M. Origin and expansion of the world's most widespread pinniped: range-wide population genomics of the harbour seal (Phoca vitulina). Mol Ecol 2022; 31:1682-1699. [PMID: 35068013 PMCID: PMC9306526 DOI: 10.1111/mec.16365] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 01/07/2022] [Accepted: 01/11/2022] [Indexed: 11/26/2022]
Abstract
The harbour seal (Phoca vitulina) is the most widely distributed pinniped, occupying a wide variety of habitats and climatic zones across the Northern Hemisphere. Intriguingly, the harbour seal is also one of the most philopatric seals, raising questions as to how it colonised virtually the whole of the Northern Hemisphere. To shed light on the origin, remarkable range expansion, population structure and genetic diversity of this species, we used genotyping-by-sequencing to analyse ~13,500 biallelic SNPs from 286 individuals sampled from 22 localities across the species' range. Our results point to a Northeast Pacific origin, colonisation of the North Atlantic via the Canadian Arctic, and subsequent stepping-stone range expansions across the North Atlantic from North America to Europe, accompanied by a successive loss of genetic diversity. Our analyses further revealed a deep divergence between modern North Pacific and North Atlantic harbour seals, with finer-scale genetic structure at regional and local scales consistent with strong philopatry. The study provides new insights into the harbour seal's remarkable ability to colonise and adapt to a wide range of habitats. Furthermore, it has implications for current harbour seal subspecies delineations and highlights the need for international and national red lists and management plans to ensure the protection of genetically and demographically isolated populations.
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Affiliation(s)
- Xiaodong Liu
- Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Denmark
| | | | - Sandra M Granquist
- Icelandic Seal Centre, Höfðabraut 6, 530, Hvammstangi, Iceland.,Marine and Freshwater Research Institute, Institute of Freshwater Fisheries Fornubúðir 5, 220, Hafnarfjörður, Iceland
| | | | - Rune Dietz
- Marine Mammal Research, Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Jonas Teilmann
- Marine Mammal Research, Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Anders Galatius
- Marine Mammal Research, Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | | | - Greg O Corry-Crowe
- Wildlife Evolution and Behavior Program, Florida Atlantic University, USA
| | - Karin Harding
- Department of Biological and Environmental Sciences, University of Gothenburg, Sweden
| | | | - Ailsa Hall
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St. Andrews, UK, KY16 8LB
| | - Emma L Carroll
- School of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Yumi Kobayashi
- Laboratory of Animal Ecology, Research Faculty of Agriculture, Hokkaido University, Japan
| | - Mike Hammill
- Maurice Lamontagne Institute, Fisheries and Oceans Canada, P.O. Box 1000, Mont-Joli, QC, Canada
| | - Garry Stenson
- Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, P.O. Box 5667, St. John's NL, Canada
| | | | | | - Kit M Kovacs
- Norwegian Polar Institute, Fram Centre, 9296, Tromsø, Norway
| | | | - Joseph I Hoffman
- Department of Animal Behaviour, University of Bielefeld, 33501, Bielefeld, Germany.,British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET, UK
| | - Simon J Goodman
- School of Biology, Faculty of Biological Sciences, University of Leeds, UK
| | - Filipe G Vieira
- Center for Genomic Medicine, Copenhagen University Hospitalet, Denmark
| | - Rasmus Heller
- Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Denmark
| | - Ida Moltke
- Section for Computational and RNA Biology, Department of Biology, University of Copenhagen, Denmark
| | - Morten Tange Olsen
- Section for Evolutionary Genomics, Globe Institute, University of Copenhagen, Denmark
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