Age of European silver eels during a period of declining abundance in Norway
Abstract 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, esp...
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ftdoajarticles:oai:doaj.org/article:71332fc7f5a54094bf99010a51e45ecd 2023-05-15T13:27:25+02:00 Age of European silver eels during a period of declining abundance in Norway Caroline M. F. Durif Ola H. Diserud Odd Terje Sandlund Eva B. Thorstad Russell Poole Knut Bergesen Rosa H. Escobar‐Lux Steven Shema Leif Asbjørn Vøllestad 2020-06-01T00:00:00Z https://doi.org/10.1002/ece3.6234 https://doaj.org/article/71332fc7f5a54094bf99010a51e45ecd EN eng Wiley https://doi.org/10.1002/ece3.6234 https://doaj.org/toc/2045-7758 2045-7758 doi:10.1002/ece3.6234 https://doaj.org/article/71332fc7f5a54094bf99010a51e45ecd Ecology and Evolution, Vol 10, Iss 11, Pp 4801-4815 (2020) aging method Anguilla anguilla catchment endangered species growth migration Ecology QH540-549.5 article 2020 ftdoajarticles https://doi.org/10.1002/ece3.6234 2022-12-31T05:24:29Z Abstract 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. Article in Journal/Newspaper Anguilla anguilla European eel Directory of Open Access Journals: DOAJ Articles Norway Ecology and Evolution 10 11 4801 4815 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
aging method Anguilla anguilla catchment endangered species growth migration Ecology QH540-549.5 |
spellingShingle |
aging method Anguilla anguilla catchment endangered species growth migration Ecology QH540-549.5 Caroline M. F. Durif Ola H. Diserud Odd Terje Sandlund Eva B. Thorstad Russell Poole Knut Bergesen Rosa H. Escobar‐Lux Steven Shema Leif Asbjørn Vøllestad Age of European silver eels during a period of declining abundance in Norway |
topic_facet |
aging method Anguilla anguilla catchment endangered species growth migration Ecology QH540-549.5 |
description |
Abstract 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 |
Article in Journal/Newspaper |
author |
Caroline M. F. Durif Ola H. Diserud Odd Terje Sandlund Eva B. Thorstad Russell Poole Knut Bergesen Rosa H. Escobar‐Lux Steven Shema Leif Asbjørn Vøllestad |
author_facet |
Caroline M. F. Durif Ola H. Diserud Odd Terje Sandlund Eva B. Thorstad Russell Poole Knut Bergesen Rosa H. Escobar‐Lux Steven Shema Leif Asbjørn Vøllestad |
author_sort |
Caroline M. F. Durif |
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 |
Wiley |
publishDate |
2020 |
url |
https://doi.org/10.1002/ece3.6234 https://doaj.org/article/71332fc7f5a54094bf99010a51e45ecd |
geographic |
Norway |
geographic_facet |
Norway |
genre |
Anguilla anguilla European eel |
genre_facet |
Anguilla anguilla European eel |
op_source |
Ecology and Evolution, Vol 10, Iss 11, Pp 4801-4815 (2020) |
op_relation |
https://doi.org/10.1002/ece3.6234 https://doaj.org/toc/2045-7758 2045-7758 doi:10.1002/ece3.6234 https://doaj.org/article/71332fc7f5a54094bf99010a51e45ecd |
op_doi |
https://doi.org/10.1002/ece3.6234 |
container_title |
Ecology and Evolution |
container_volume |
10 |
container_issue |
11 |
container_start_page |
4801 |
op_container_end_page |
4815 |
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1766398280361574400 |