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Report of the ICES/HELCOM Workshop on Flatfish in the Baltic Sea (WKFLABA)

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posted on 2023-01-18, 12:08 authored by ICESICES

The ICES/HELCOM Workshop on Flatfish in the Baltic Sea WKFLABA took place in Öregrund (Sweden), 8-11 November 2010 (Chaired by Jan Horbowy, Poland, Ann-Britt Florin and Didzis Ustups, Sweden). In total, 16 ICES and HELCOM experts from 8 countries attended the meeting. The objectives of the meeting were to review the flatfish population structure in the Baltic Sea and to suggest possible stock assess-ment units from biological point of view. Trial assessments were also conducted for those stocks with sufficient existing data.
The agenda of the meeting was divided into two periods, the first for literature re-views and the second for data analyses and stock assessments.  
In total 17 populations of flatfish (11 flounder, 3 plaice and 3 dab) were identified in the Baltic Sea. Lack of available information for turbot and brill did not allow identifying stock structure for these species
The workshop agreed that only the improved ageing methodology (sliced and stained or broken and burned) shall be used for all flatfish species.  Long time series with new age data were available only for some stocks. For the other stocks the new methodology has only been used during the last few years. This reduces the possibility to use classical cohort based stock assessments models (e.g., XSA, ICA) for these stocks.
Therefore, alternative models for evaluations of dynamics and state of flatfish stocks were discussed. The following groups of methods were considered: 

• Production models
• Difference models
• The models using Random Walk (RW)
• Length based Cohort Analysis
• Simple methods allowing approximate evaluation of exploitation level (catch curve analysis, total mortality estimates using mean age or mean length in the stock)

Different alternative models were used for estimation of biomass and/or mortality of flounder (Southern Baltic, Bay of Gdansk, Eastern Gotland, Swedish east coast, Estonian coast of Gulf of Finland) and turbot (in ICES SD 28) populations. Due to time constraints the workshop was just able to initiate some analyses and the obtained results by no way may be considered as final assessments. A lot of intersessional work is needed to compile the data and test the data and the models.  Then, depending on reliability of results and diagnostics of the models, the assessment method for given stock might be proposed.  


Published under the auspices of the following ICES Steering Group or Committee

  • ACOM

Published under the auspices of the following ICES Expert Group or Strategic Initiative

WKFLABA; Workshops - ACOM


ICES Expert Group Reports

Meeting details

8 - 11 November 2010; Öregrund, Sweden

Recommended citation

ICES. 2010. Report of the ICES/HELCOM Workshop on Flatfish in the Baltic Sea (WKFLABA), 8 - 11 November 2010, Öregrund, Sweden. ICES CM 2010/ACOM:68. 85 pp. https://doi.org/10.17895/ices.pub.19280705