The Forgotten Requirement for Age Validation in Fisheries Biology

A survey of 500 studies published between 1907 and 1980 that included estimates of fish age indicated that only 65% mentioned age validation or attempted to validate the ageing technique. In less than 3% was the technique validated for all age classes. Among the 35% that did not consider age validation, many did not consider the possibility that ages may be incorrect. Among 75 additional publications published in primary journals between 1965 and 1980 that assessed stock dynamics and used fish ages, only 40% mentioned or attempted age validation, and none successfully validated all age groups used in the analysis. Many investigators continue to neglect the critical study of age validation despite the clear direction of the early work on age determination. We show that estimated ages greater than the maximum validated age must not be considered accurate. Use of inaccurate ages has caused serious errors in the management and understanding of fish populations. Only by mark-recapture studies or use of known-age fish can all age classes in a population be validated. If such studies are not possible, fish should be aged by several methods, and the possibility of errors in age estimates must be considered. Received April 5, 1983 Accepted August 9, 1983