Age of European silver eels during a period of declining abundance in Norway
The European eel (Anguilla anguilla) is critically endangered throughout its range. Knowledge about age distribution of future spawners (silver eels) is essential to monitor the status and contribute to the recovery of this species. Determination of age in anguillid eels is challenging, especially i...
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ftpubmed:oai:pubmedcentral.nih.gov:7297751 2023-05-15T13:28:03+02:00 Age of European silver eels during a period of declining abundance in Norway Durif, Caroline M. F. Diserud, Ola H. Sandlund, Odd Terje Thorstad, Eva B. Poole, Russell Bergesen, Knut Escobar‐Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn 2020-04-12 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297751/ https://doi.org/10.1002/ece3.6234 en eng John Wiley and Sons Inc. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297751/ http://dx.doi.org/10.1002/ece3.6234 © 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. CC-BY Ecol Evol Original Research Text 2020 ftpubmed https://doi.org/10.1002/ece3.6234 2020-06-21T00:51:28Z The European eel (Anguilla anguilla) is critically endangered throughout its range. Knowledge about age distribution of future spawners (silver eels) is essential to monitor the status and contribute to the recovery of this species. Determination of age in anguillid eels is challenging, especially in eels from the northern part of the distribution area where growth is slow and age at maturation can be up to 30 years or more. Eels from the river Imsa in Norway have been monitored since 1975, and this reference time series has been used to assess the stock at the European level. Population dynamics in this catchment were analyzed during the late 1980s by estimating ages on whole cleared otoliths. However, techniques for revealing annual increments on otoliths have evolved over the years sometimes yielding significant differences in age estimates. In this study, the historical otolith data were reanalyzed using a grinding and polishing method rather than reading the whole otolith. The new age estimates were considerably higher than the previous ones, sometimes by up to 29 years. Since the 1980s, mean age of silver eels only slightly increased (from 19 to 21 years in the 2010s). This was mainly due to the disappearance of younger silver eels (<15 years) in the 2010s. The new age estimates agreed with the steep decline in recruitment which occurred in the late 1980s in the Imsa catchment. Mean growth (30 mm/year, min–max: 16–64 mm/year) has not changed since the 1980s, although density in the catchment has decreased. Revealing and reading age of slow‐growing eels remain a challenge but adding a measure of otolith reading uncertainty may improve age data collection and contribute to recovery measures for this species. Text Anguilla anguilla European eel PubMed Central (PMC) Norway Ecology and Evolution 10 11 4801 4815 |
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PubMed Central (PMC) |
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English |
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Original Research |
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Original Research Durif, Caroline M. F. Diserud, Ola H. Sandlund, Odd Terje Thorstad, Eva B. Poole, Russell Bergesen, Knut Escobar‐Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn Age of European silver eels during a period of declining abundance in Norway |
topic_facet |
Original Research |
description |
The European eel (Anguilla anguilla) is critically endangered throughout its range. Knowledge about age distribution of future spawners (silver eels) is essential to monitor the status and contribute to the recovery of this species. Determination of age in anguillid eels is challenging, especially in eels from the northern part of the distribution area where growth is slow and age at maturation can be up to 30 years or more. Eels from the river Imsa in Norway have been monitored since 1975, and this reference time series has been used to assess the stock at the European level. Population dynamics in this catchment were analyzed during the late 1980s by estimating ages on whole cleared otoliths. However, techniques for revealing annual increments on otoliths have evolved over the years sometimes yielding significant differences in age estimates. In this study, the historical otolith data were reanalyzed using a grinding and polishing method rather than reading the whole otolith. The new age estimates were considerably higher than the previous ones, sometimes by up to 29 years. Since the 1980s, mean age of silver eels only slightly increased (from 19 to 21 years in the 2010s). This was mainly due to the disappearance of younger silver eels (<15 years) in the 2010s. The new age estimates agreed with the steep decline in recruitment which occurred in the late 1980s in the Imsa catchment. Mean growth (30 mm/year, min–max: 16–64 mm/year) has not changed since the 1980s, although density in the catchment has decreased. Revealing and reading age of slow‐growing eels remain a challenge but adding a measure of otolith reading uncertainty may improve age data collection and contribute to recovery measures for this species. |
format |
Text |
author |
Durif, Caroline M. F. Diserud, Ola H. Sandlund, Odd Terje Thorstad, Eva B. Poole, Russell Bergesen, Knut Escobar‐Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn |
author_facet |
Durif, Caroline M. F. Diserud, Ola H. Sandlund, Odd Terje Thorstad, Eva B. Poole, Russell Bergesen, Knut Escobar‐Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn |
author_sort |
Durif, Caroline M. F. |
title |
Age of European silver eels during a period of declining abundance in Norway |
title_short |
Age of European silver eels during a period of declining abundance in Norway |
title_full |
Age of European silver eels during a period of declining abundance in Norway |
title_fullStr |
Age of European silver eels during a period of declining abundance in Norway |
title_full_unstemmed |
Age of European silver eels during a period of declining abundance in Norway |
title_sort |
age of european silver eels during a period of declining abundance in norway |
publisher |
John Wiley and Sons Inc. |
publishDate |
2020 |
url |
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297751/ https://doi.org/10.1002/ece3.6234 |
geographic |
Norway |
geographic_facet |
Norway |
genre |
Anguilla anguilla European eel |
genre_facet |
Anguilla anguilla European eel |
op_source |
Ecol Evol |
op_relation |
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297751/ http://dx.doi.org/10.1002/ece3.6234 |
op_rights |
© 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1002/ece3.6234 |
container_title |
Ecology and Evolution |
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10 |
container_issue |
11 |
container_start_page |
4801 |
op_container_end_page |
4815 |
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1766401956181442560 |