Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment
The oldest and largest individuals are disappearing from many fish stocks worldwide as a result of overexploitation. This has been suggested to impair recruitment through decreasing the reproductive capacity of the spawners and increasing the mortality rate of the offspring. By using a time series o...
Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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Online Access: | http://dx.doi.org/10.1139/f07-185 http://www.nrcresearchpress.com/doi/pdf/10.1139/f07-185 |
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crcansciencepubl:10.1139/f07-185 2024-05-19T07:40:34+00:00 Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment Ottersen, Geir 2008 http://dx.doi.org/10.1139/f07-185 http://www.nrcresearchpress.com/doi/pdf/10.1139/f07-185 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Fisheries and Aquatic Sciences volume 65, issue 3, page 523-534 ISSN 0706-652X 1205-7533 journal-article 2008 crcansciencepubl https://doi.org/10.1139/f07-185 2024-05-02T06:51:25Z The oldest and largest individuals are disappearing from many fish stocks worldwide as a result of overexploitation. This has been suggested to impair recruitment through decreasing the reproductive capacity of the spawners and increasing the mortality rate of the offspring. By using a time series on spawners biomass by age class for Arcto-Norwegian cod (Gadus morhua) from 1913–2004, I have documented pronounced changes in the spawning stock, including a trend towards younger fish, a less diverse distribution across ages, and a declining proportion of repeat spawners. Despite the total spawning stock biomass (SSB) being at similar levels now as in 1933, the mean age in the SSB has declined from 10–12.5 years to 7–8 years during the study period, and the percentage of fish of age 10 or above in the SSB has decreased from ~97% to ~10%. Contrary to earlier theoretical and experimental studies, no clear link between age structure and recruitment was found here. Recruitment to the Arcto-Norwegian cod stock may thus be more robust towards spawner juvenation than expected, possibly because of strong recruitment compensation. Article in Journal/Newspaper Gadus morhua Canadian Science Publishing Canadian Journal of Fisheries and Aquatic Sciences 65 3 523 534 |
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Canadian Science Publishing |
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English |
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The oldest and largest individuals are disappearing from many fish stocks worldwide as a result of overexploitation. This has been suggested to impair recruitment through decreasing the reproductive capacity of the spawners and increasing the mortality rate of the offspring. By using a time series on spawners biomass by age class for Arcto-Norwegian cod (Gadus morhua) from 1913–2004, I have documented pronounced changes in the spawning stock, including a trend towards younger fish, a less diverse distribution across ages, and a declining proportion of repeat spawners. Despite the total spawning stock biomass (SSB) being at similar levels now as in 1933, the mean age in the SSB has declined from 10–12.5 years to 7–8 years during the study period, and the percentage of fish of age 10 or above in the SSB has decreased from ~97% to ~10%. Contrary to earlier theoretical and experimental studies, no clear link between age structure and recruitment was found here. Recruitment to the Arcto-Norwegian cod stock may thus be more robust towards spawner juvenation than expected, possibly because of strong recruitment compensation. |
format |
Article in Journal/Newspaper |
author |
Ottersen, Geir |
spellingShingle |
Ottersen, Geir Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment |
author_facet |
Ottersen, Geir |
author_sort |
Ottersen, Geir |
title |
Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment |
title_short |
Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment |
title_full |
Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment |
title_fullStr |
Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment |
title_full_unstemmed |
Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod ( Gadus morhua) and possible consequences for recruitment |
title_sort |
pronounced long-term juvenation in the spawning stock of arcto-norwegian cod ( gadus morhua) and possible consequences for recruitment |
publisher |
Canadian Science Publishing |
publishDate |
2008 |
url |
http://dx.doi.org/10.1139/f07-185 http://www.nrcresearchpress.com/doi/pdf/10.1139/f07-185 |
genre |
Gadus morhua |
genre_facet |
Gadus morhua |
op_source |
Canadian Journal of Fisheries and Aquatic Sciences volume 65, issue 3, page 523-534 ISSN 0706-652X 1205-7533 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/f07-185 |
container_title |
Canadian Journal of Fisheries and Aquatic Sciences |
container_volume |
65 |
container_issue |
3 |
container_start_page |
523 |
op_container_end_page |
534 |
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1799480139539546112 |