International Council for the Exploration of the Sea
WKARWHG2 2016_Full report.pdf (1.4 MB)

Report of the Workshop on Age estimation of Whiting (Merlangius merlangus) (WKARWHG2)

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posted on 2016-01-01, 00:00 authored by ICESICES

Based on the results of a full-scale otolith exchange held in 2015 (Smith, 2015) The Working Group on Biological Parameters (WGBIOP) identified the need for an age reading workshop on whiting otoliths (WKARWHG2). This workshop was hosted by Centre for Environment Fisher-ies and Aquaculture Science (Lowestoft, UK 22–25 November 2016. Seventeen age readers from nine countries (Belgium, France, Denmark, Norway, Germany, UK, Northern Ireland, Southern Ireland, and Scotland) participated in the workshop. The workshop was chaired by Joanne Smith (UK) and Suzy End (UK) acted as a Workshop supporting expert.

Two otoliths sets, an exercise set of 105 otoliths and a subsample set of 50 otoliths from the orig-inal exchange otolith set were aged during the workshop. The exercise set were read first, to highlight any issues/disagreements between age readers and the possible reasons for these. Fol-lowing recommendations from WGBIOP otoliths from area ICES Division 4b were included in this exercise as this area was not covered in the original exchange set. Readers had the option of ageing the otolith using both an image and the actual otolith under a stereomicroscope. Only a small number of readers chose to use both methods, most choosing to age using images only. After the exercise set was read, the results were presented and differences between interpreta-tions were discussed.

In addition, a small group of experienced section and whole otolith readers carried out a reading exercise (20 otoliths) to compare the percentage agreement obtained by readers using different otolith preparation methods. Since the results from this small exercise were not encouraging, the conclusion from this exercise was that action needed to be taken to ensure that agreements re-main high regardless of preparation method used. Also, there were few examples from 4a in the original exchange, which is an area used by Norway, Denmark, and Scotland The additional mini exchange will provide them with a more complete dataset to work with which should help with future exchanges. Post workshop, readers who routinely read whiting otoliths, whole or broken, agreed to conduct an otolith exchange in an attempt to clarify, the level of agreement between these readers and where disagreements occur, the possible reasons for these.


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ICES Expert Group Reports

Recommended citation

ICES. 2017. Report of the Workshop on Age estimation of Whiting (Merlangius mer-langus) (WKARWHG2), 22-25 November 2016, Lowestoft, UK. ICES CM 2016\SSGIEOM:15. 47 pp.

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