Why is age determination of Baltic cod (Gadus morhua) so difficult?
The aim of this study was to evaluate the consistency of three methods for assigning annuli in adult Baltic cod otoliths. The methods examined were (i) daily increment patterns, (ii) opacity profiles, and (iii) traditional age reading. Frequency distributions of the distance from the nucleus to the...
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2010
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Online Access: | https://orbit.dtu.dk/en/publications/767348e2-001d-4343-945c-90a86dd7f1dc https://doi.org/10.1093/icesjms/fsq023 |
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ftdtupubl:oai:pure.atira.dk:publications/767348e2-001d-4343-945c-90a86dd7f1dc 2024-09-15T18:07:18+00:00 Why is age determination of Baltic cod (Gadus morhua) so difficult? Hüssy, Karin 2010 https://orbit.dtu.dk/en/publications/767348e2-001d-4343-945c-90a86dd7f1dc https://doi.org/10.1093/icesjms/fsq023 eng eng https://orbit.dtu.dk/en/publications/767348e2-001d-4343-945c-90a86dd7f1dc info:eu-repo/semantics/restrictedAccess Hüssy , K 2010 , ' Why is age determination of Baltic cod (Gadus morhua) so difficult? ' , ICES Journal of Marine Science , vol. 67 , no. 6 , pp. 1198-1205 . https://doi.org/10.1093/icesjms/fsq023 article 2010 ftdtupubl https://doi.org/10.1093/icesjms/fsq023 2024-07-08T23:51:45Z The aim of this study was to evaluate the consistency of three methods for assigning annuli in adult Baltic cod otoliths. The methods examined were (i) daily increment patterns, (ii) opacity profiles, and (iii) traditional age reading. Frequency distributions of the distance from the nucleus to the different zones showed that the first annulus of traditional age reading missed the first zone of both increment and opacity methods, but overlapped with the second zone identified by these methods. This pattern did not continue over subsequent zones. Frequency distributions of increment patterns were similar to opacity patterns. However, within individual fish, the co-occurrence of overlap between the two patterns was random. In cases where there was overlap, translucent zone formation started just before the disappearance of visible increments. Overlap in 1 year did not necessarily lead to a consistent pattern the following year, and overlap was not influenced by sex or fish size. The results suggest that otolith opacity in Baltic cod is not associated with seasonal patterns in daily increment structure and that traditional age determination based on otolith opacity yields highly uncertain estimates of age. Article in Journal/Newspaper Gadus morhua Technical University of Denmark: DTU Orbit ICES Journal of Marine Science 67 6 1198 1205 |
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Open Polar |
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Technical University of Denmark: DTU Orbit |
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ftdtupubl |
language |
English |
description |
The aim of this study was to evaluate the consistency of three methods for assigning annuli in adult Baltic cod otoliths. The methods examined were (i) daily increment patterns, (ii) opacity profiles, and (iii) traditional age reading. Frequency distributions of the distance from the nucleus to the different zones showed that the first annulus of traditional age reading missed the first zone of both increment and opacity methods, but overlapped with the second zone identified by these methods. This pattern did not continue over subsequent zones. Frequency distributions of increment patterns were similar to opacity patterns. However, within individual fish, the co-occurrence of overlap between the two patterns was random. In cases where there was overlap, translucent zone formation started just before the disappearance of visible increments. Overlap in 1 year did not necessarily lead to a consistent pattern the following year, and overlap was not influenced by sex or fish size. The results suggest that otolith opacity in Baltic cod is not associated with seasonal patterns in daily increment structure and that traditional age determination based on otolith opacity yields highly uncertain estimates of age. |
format |
Article in Journal/Newspaper |
author |
Hüssy, Karin |
spellingShingle |
Hüssy, Karin Why is age determination of Baltic cod (Gadus morhua) so difficult? |
author_facet |
Hüssy, Karin |
author_sort |
Hüssy, Karin |
title |
Why is age determination of Baltic cod (Gadus morhua) so difficult? |
title_short |
Why is age determination of Baltic cod (Gadus morhua) so difficult? |
title_full |
Why is age determination of Baltic cod (Gadus morhua) so difficult? |
title_fullStr |
Why is age determination of Baltic cod (Gadus morhua) so difficult? |
title_full_unstemmed |
Why is age determination of Baltic cod (Gadus morhua) so difficult? |
title_sort |
why is age determination of baltic cod (gadus morhua) so difficult? |
publishDate |
2010 |
url |
https://orbit.dtu.dk/en/publications/767348e2-001d-4343-945c-90a86dd7f1dc https://doi.org/10.1093/icesjms/fsq023 |
genre |
Gadus morhua |
genre_facet |
Gadus morhua |
op_source |
Hüssy , K 2010 , ' Why is age determination of Baltic cod (Gadus morhua) so difficult? ' , ICES Journal of Marine Science , vol. 67 , no. 6 , pp. 1198-1205 . https://doi.org/10.1093/icesjms/fsq023 |
op_relation |
https://orbit.dtu.dk/en/publications/767348e2-001d-4343-945c-90a86dd7f1dc |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1093/icesjms/fsq023 |
container_title |
ICES Journal of Marine Science |
container_volume |
67 |
container_issue |
6 |
container_start_page |
1198 |
op_container_end_page |
1205 |
_version_ |
1810444688003432448 |