Ahead of Print article · Journal article
Seeking the True Time: Exploring Otolith Chemistry as an Age-Determination Tool
Swedish University of Agricultural Sciences1
National Institute of Aquatic Resources, Technical University of Denmark2
Section for Oceans and Arctic, National Institute of Aquatic Resources, Technical University of Denmark3
Section for Monitoring and Data, National Institute of Aquatic Resources, Technical University of Denmark4
Russian Federal Research Institute of Fisheries and Oceanography5
National Marine Fisheries Research Institute6
Swedish Museum of Natural History7
Fish otoliths' chronometric properties make them useful for age and growth rate estimation in fisheries management. For the Eastern Baltic Sea cod stock (Gadus morhua), unclear seasonal growth zones in otoliths have resulted in unreliable age and growth information. Here, a new age estimation method based on seasonal patterns in trace elemental otolith incorporation was tested for the first time and compared with the traditional method of visually counting growth zones, using otoliths from the Baltic and North seas.
Various trace elemental ratios, linked to fish metabolic activity (higher in summer) or external environment (migration to colder, deeper habitats with higher salinity in winter), were tested for age estimation based on assessing their seasonal variations in concentration. Mg:Ca and P:Ca, both proxies for growth and metabolic activity, showed greatest seasonality and therefore have the best potential to be used as chemical clocks.
Otolith image readability was significantly lower in the Baltic than in the North Sea. The chemical (novel) method had an overall greater precision and percent agreement among readers (11.2%, 74.0%) than the visual (traditional) method (23.1%, 51.0%). Visual readers generally selected more highly contrasting zones as annuli whereas the chemical readers identified brighter regions within the first two annuli, and darker zones thereafter.
Visual estimates produced significantly higher, more variable ages than did the chemical ones. Based on the analyses in our study, we suggest that otolith micro-chemistry is a promising alternative ageing method for fish populations difficult to age, such as the Eastern Baltic cod. This article is protected by copyright.
All rights reserved.
Language: | English |
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Publisher: | Blackwell Publishing Ltd |
Year: | 2020 |
Pages: | 552-565 |
ISSN: | 10958649 and 00221112 |
Types: | Ahead of Print article and Journal article |
DOI: | 10.1111/jfb.14422 |
ORCIDs: | 0000-0002-5120-4797 , 0000-0003-3716-8555 , Hüssy, Karin and 0000-0003-4910-5236 |