Report of the Workshop on Age Reading of European and American Eel (WKAREA2)
The workshop commenced with the analysis of the results of the experienced reader inter calibration exercise that had been carried out several months previous the meeting. This intercalibration exercise was based on image exchange for both species. The readings had been performed on a web platform device allowing the positioning of age checks on the pictures and recording the number of checks identified by each reader. A total of 21 readers participated to the exchange. A collection of 117 European eel pictures and 44 American eel otolith pictures were used for the exchange. The overall agreement rate of the readings with the modal age ranged from 66.2% to 13.2%. The results showed that more agreement would have been obtained if the reading rules had been applied more consistently. Some readers discarded some “difficult” otoliths. The absence of metadata such as the location, date of capture and habitat type of the otolith was also identified as a source of misinterpretation of growth patterns. It was recognized for future readings that metadata should be included and that all otoliths would be read, with the addition of a reading confidence parameter. A reference collection composed of 38 A. Anguilla and 19 A. rostrata known age otolith pictures was set up, with one blind file and one fully annotated file. The manual was updated with more precisions included for the different preparation protocols. A protocol for age reading and training age reading and routine age reading was proposed, including the use of the reference collection.
Includes Annex 5: Manual for the ageing of Atlantic Eel, produced by the Workshop participants.
Published under the auspices of the following ICES Steering Group or Committee