Slave to the rhythm: seasonal signals in otolith microchemistry reveal age of eastern Baltic cod (Gadus morhua)

Hüssy, K., Gröger, J., Heidemann, F., Hinrichsen, Hans-Harald and Marohn, L. (2016) Slave to the rhythm: seasonal signals in otolith microchemistry reveal age of eastern Baltic cod (Gadus morhua) ICES Journal of Marine Science, 73 (4). pp. 1019-1032. DOI 10.1093/icesjms/fsv247.

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Annual growth zones in cod otoliths from the eastern Baltic stock are less discrete than in other cod stocks leading to biased age reading, which recently led to a failure of age-based assessment in the eastern Baltic cod stock. In this study, we explored the applicability of minor and trace element patterns in cod otoliths for age determination. By first identifying elements of interest in a stock without ageing problems, western Baltic cod, we then tested their applicability on another stock without ageing problems, North Sea cod, and finally applied this knowledge to estimate age of eastern Baltic cod. In western Baltic cod, matching patterns with respect to occurrence of minima and maxima in both otolith opacity and element concentrations were found for Cu, Zn, and Rb, and inverse patterns with Mg and Mn. No match was found for Pb, Ba, and Sr. In the test stock, the North Sea cod, the same patterns in Cu, Zn, Rb, Mg, and Mn signals occurred. All eastern Baltic cod with low visual contrast between growth zones exhibited clearly defined synchronous cycles in Cu, Zn, Rb and Pb. Using a combined finite differencing method and structural break models approach, the statistical significance of the local profile minima were identified, based on which their age could be estimated. Despite extensive environmental differences between the three areas examined, the element concentrations of Cu, Zn, and Rb were strongly correlated in all individuals with similar correlations in all three areas, suggesting that the incorporation mechanisms are the same for these elements and independent of environmental concentrations.

Document Type: Article
Additional Information: WOS:000373233600004
Keywords: age estimation, Atlantic cod, microchemistry, otolith, seasonal patterns
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Evolutionary Ecology of Marine Fishes
Refereed: Yes
DOI etc.: 10.1093/icesjms/fsv247
ISSN: 1054-3139
Projects: INSPIRE
Date Deposited: 14 Jan 2016 09:34
Last Modified: 19 Dec 2017 12:48

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