International Council for the Exploration of the Sea
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Report of the Workshop on Sardine Otolith Age Reading

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posted on 2022-11-14, 09:40 authored by Eduardo Soares, Alexandre Morais, Alexandra Silva, Pablo Carrera, Afonso Jorge, Inaki Rico, Quena Peleteiro, Hughes Evano

An otolith exchange for sardine was carried out in July 2000 within the framework of EU Project PELASSES to standardise age reading criteria between project participants. A total of 359 otolith pairs were analysed from sardine samples collected in the spring acoustic surveys covering the area from the English Channel to the Gulf of Cadiz. Disagreement in age readings of young (age groups 1 and 2) and old fish (from age group 4 onwards) and on otoliths from the southern areas (Algarve and Cadiz) were the main problems identified during the exchange and later discussed on a workshop. The consistency within readers was also checked during the

workshop. Identification of the first annual ring was the main problem on younger ages. In older fish, discrimination of rings near the otolith edge caused most of the disagreements. These difficulties are complicated in otoliths from the southern areas, due to the less clear structure and to the frequency of occurrence of false rings. A poor consistency within readers was also observed. The present workshop outlined an improvement in sardine age reading performance since the last otolith exchange with acceptable levels of agreement, precision and accuracy for young individuals (age groups one to three). However, ageing older individuals, otoliths from the southern area and within reader consistency are still a matter of concern.





Published by IPIMAR Scientific and Technical Reports nº14

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