Workshop 2 on age reading of sea bass (Dicentrarchus labrax) (WKARDL2)

Workshop 2 on age reading of sea bass (Dicentrarchus labrax) (WKARDL2) focused on ageing criteria for this species after the first meeting in 2015 (WKARDL). Ten scientists from Cefas, ILVO, and Ifremer participated in this workshop. The workshop aimed to collate information on existing ageing protocols and the used calcified pieces to better standardize the interpretation of annual growth rings and then the ageing of sea bass. The first step was to review information on sea bass age estimations, otolith exchanges, workshops, and validation work done so far. For sea bass, the used calcified structures were not always the same; there are scale, whole otolith, and stained section of the otolith. During the last exchange in 2020 (100 images from Eastern English Channel; 27.7d), the results showed some differences between scales and sectioned and stained otolith. From the discussion around the interpreted images, the guidelines for scale and stained otolith interpretation and common issues were realized. After several discussions around the ageing criteria on both calcified structures, the new ageing exercise was achieved on 42 images using the SmartDots platform. For the scales, the average percentage agreement (PA) was 80%, with an average Coefficient of Variation (CV) of 7%. For sectioned and stained otoliths, the av-erage percentage agreement (PA) was 88% with an average Coefficient of Variation (CV) of 6%. The results of the workshop showed that stained otoliths give a better agreement between read-ers than scales but scales are much easier to sample than the otoliths for various reasons. Conse-quently, this group recommended that the ageing of sea bass in routine will be carried out from the scales and where possible, otoliths could be collected to help determine the age