Quality issues in the use of otoliths for fish age estimation

Abstract

Quality issues in fish age estimation, which historically have focused mainly on inadequacies in the validation process, are increasingly directed at ways to measure and control the errors or inconsistencies in the application of established and validated methods. The process of age estimation, as undertaken by human operators, involves a complex mix of pattern recognition and interpretation based on knowledge and experience. It is best characterised as a skill rather than an art. Such an approach promotes the use of well-recognised techniques designed to maintain and enhance skills that also assist in maintaining standards. The results of a questionnaire completed by representatives of over 50 ageing laboratories worldwide were used to assess current quality assurance and quality control practices. Results indicate a great diversity in attention to, and no clear consensus on desirable standards for, quality issues, including staff training, use of reference sets, reading protocols, and post-reading analyses. This is considered more likely to reflect variation in awareness of the importance of quality issues than variation in the need for quality assurance and quality control measures. Greater attention to a range of quality control processes is urged, particularly the more regular use of reference sets.