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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Online Access: | https://hdl.handle.net/11250/2651278 https://doi.org/10.1002/ece3.6234 |
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ftninstnf:oai:brage.nina.no:11250/2651278 2024-06-23T07:45:32+00:00 Age of European silver eels during a period of declining abundance in Norway Durif, Caroline Diserud, Ola Håvard Sandlund, Odd Terje Thorstad, Eva Bonsak Poole, Russell Bergesen, Knut Aanestad Escobar-Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn Noreg, Norge, Norway 2020 application/pdf https://hdl.handle.net/11250/2651278 https://doi.org/10.1002/ece3.6234 eng eng urn:issn:2045-7758 https://hdl.handle.net/11250/2651278 https://doi.org/10.1002/ece3.6234 cristin:1806584 Navngivelse 4.0 Internasjonal http://creativecommons.org/licenses/by/4.0/deed.no © 2020 The Authors. Ecology and Evolution aging method Anguilla anguilla catchment endangered species growth migration otolith river sex ratio VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 Journal article 2020 ftninstnf https://doi.org/10.1002/ece3.6234 2024-06-07T03:57:56Z 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. publishedVersion Article in Journal/Newspaper Anguilla anguilla European eel Norwegian Institute for Nature Research: Brage NINA Norway Ecology and Evolution 10 11 4801 4815 |
institution |
Open Polar |
collection |
Norwegian Institute for Nature Research: Brage NINA |
op_collection_id |
ftninstnf |
language |
English |
topic |
aging method Anguilla anguilla catchment endangered species growth migration otolith river sex ratio VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 |
spellingShingle |
aging method Anguilla anguilla catchment endangered species growth migration otolith river sex ratio VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 Durif, Caroline Diserud, Ola Håvard Sandlund, Odd Terje Thorstad, Eva Bonsak Poole, Russell Bergesen, Knut Aanestad Escobar-Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn Age of European silver eels during a period of declining abundance in Norway |
topic_facet |
aging method Anguilla anguilla catchment endangered species growth migration otolith river sex ratio VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 |
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. publishedVersion |
format |
Article in Journal/Newspaper |
author |
Durif, Caroline Diserud, Ola Håvard Sandlund, Odd Terje Thorstad, Eva Bonsak Poole, Russell Bergesen, Knut Aanestad Escobar-Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn |
author_facet |
Durif, Caroline Diserud, Ola Håvard Sandlund, Odd Terje Thorstad, Eva Bonsak Poole, Russell Bergesen, Knut Aanestad Escobar-Lux, Rosa H. Shema, Steven Vøllestad, Leif Asbjørn |
author_sort |
Durif, Caroline |
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 |
publishDate |
2020 |
url |
https://hdl.handle.net/11250/2651278 https://doi.org/10.1002/ece3.6234 |
op_coverage |
Noreg, Norge, Norway |
geographic |
Norway |
geographic_facet |
Norway |
genre |
Anguilla anguilla European eel |
genre_facet |
Anguilla anguilla European eel |
op_source |
Ecology and Evolution |
op_relation |
urn:issn:2045-7758 https://hdl.handle.net/11250/2651278 https://doi.org/10.1002/ece3.6234 cristin:1806584 |
op_rights |
Navngivelse 4.0 Internasjonal http://creativecommons.org/licenses/by/4.0/deed.no © 2020 The Authors. |
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 |
_version_ |
1802640657815175168 |