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EXECUTIVE SUMMARY

The Working Group on Stock Assessment of Demersal Species (WGSAD) benchmark session for the assessment of common sole (Solea solea) in the Adriatic Sea – geographical subarea (GSA) 17 – was held online on 12–16 April 2021. The objective of the meeting was to perform a full analysis and review of the information and methods used to provide advice on the status of the stock of common sole. The session was attended by 11 experts, including experts from the region and experts on the species and on the stock assessment models that were discussed, as well as an external reviewer.

The session investigated all available input data and carried out an analysis of the performance of two different stock assessment methodologies: the integrated model (stock synthesis; SS3) and the surplus production models (CMSY/AMSY), both tested with different assumptions and/or input data series.

The ensemble modelling approach using SS3 was used to present final results based on alternative hypotheses of selectivity, natural mortality and steepness (18 runs). This is the first time an ensemble model was used in the Mediterranean to provide management advice. Common sole in GSA 17 was considered to be slightly in overexploitation and overexploited, with fishing mortality close to the reference point (F40) and biomass around 70 percent of the reference point (SSB40).