In this working document, the results of an otolith exchange 2016 on Cod (Gadus morhua) in the Celtic Sea are presented. Each year, stock assessment of cod in the Celtic Sea requires data to be compiled and compared. For example the age distribution from this year’s assessment is compared to historical data. In 2016, there has been a small number of one year olds. Consequently, the three main countries (France, Ireland and UK England) which contribute to the cod landings in Celtic Sea organised a small otolith exchange to verify the precision of age data between four readers. Mean precision of age estimate for individual fish had a coefficient of variation (CV) of 0.2% and percent agreement to modal age of 99.5%. There was only one image where two readers identified three growth rings and the other identified four growth rings.