Otolith reading bias for juvenile Atlantic bluefin tuna was detected at its 2017 assessment. To try to reduce this bias, the current standardized reading protocol was revised. The new protocol uses age estimates from the first dorsal fin ray (spine) to identify the growth increments in the otoliths removed from the same young specimen. An exchange involving 14 experienced otolith readers was conducted to verify if the new reading procedure minimized the difference between otolith and spine readings. The results showed that there is a good agreement in the first five years, but from age 6, otoliths ages tended to be higher than spine age. Some readers had difficulty following the new protocol despite being experts, which indicates that it is necessary to improve it. The use of annual band measurements has shown to be a good tool for the control of the quality of age estimates. The results indicate that we are progressing in the recognition of the deposition pattern of the first annuli. It is recommended to carry out an ageing workshop to achieve the tasks identified as necessary.