WKARAS2Report2019.pdf (3.53 MB)
Workshop on Age Reading of European Sardine (Sardina Pilchardus) (NE Atlantic and Mediterranean) (WKARAS2)
reportposted on 2023-02-23, 09:56 authored by ICESICES
The Workshop on Age reading of European Sardine (Sardinapilchardus) (NE Atlantic and Medi-terranean) [WKARAS 2] met to review the information on age determination, discuss the results of the 2017 otolith exchange, review the existing validation methods, clarify the interpretation of annual rings, and update the age reading protocol and a reference collection of well-defined oto-liths.The 2017 otolith exchange included images of otoliths’ pairs collected from fish samples taken in 11 locations. Growth and reproduction were individually analysed by the participants for age attribution following a reference age reading protocol. R scripts based on Eltink’s MS Excel spreadsheet (Eltink, 2000) following the recommendations of the “Guidelines and tools for age reading comparisons” (Eltink et al., 2000) were used for age readings comparative analyses.In order to clarify the causes of age reading discrepancies between readers, discussions based on joint analyses of projected images of selected otoliths among those used for the 2017 exchange were held during this 2019 workshop. Review of age reading criteria used for growth rings iden-tification applied in each area was undertaken and age reading validations were discussed.The use in each area of a reference collection of otoliths’ images with ≥80% of age reading agree-ment between readers was discussed and pointed out as a suitable tool to improve age readings accuracy and to contribute for a higher agreement between readers in each area. As a contribu-tion for the construction of the reference collections, a selection of images of otoliths from the 2017 exchange with ≥80% age reading agreement between the readers was undertaken during the joint discussion.In order to assess age reading discrepancies and their causes in each area and the effects of the discussions held on the reading agreement between readers, a small age reading calibration ex-ercise took place during the workshop, based on individual analysis through SmartDots of a sample of otoliths images selected from those used in the 2017 exchange. Overall the age reading agreement (PA), coefficient of Variation (CV) and Average Percentage Error (APE) obtained by advanced readers in relation to those achieved by their equivalent “experts”+”intermediate” in each area in the 2017 exchange, are not much different from each other. Despite the previous discussions on the annulus identification by image analysis during joint sessions, difficulties per-sisted mainly on the edge type classification and on the first growth ring identification.A few recommendations come out from the discussions held during WKARAS2: exchanges should preferably be based on the structure analyses of samples of otoliths complemented by their images in SmartDots, the implementation in each area of routine otoliths age reading ex-changes, regular age reading validation studies in each area and otoliths’ images reference col-lections should be enriched by more quality images along time.
Published under the auspices of the following ICES Steering Group or Committee