Each otolith was aged with two blind reads performed at least 3 weeks apart by a single
reader counting the otolith annuli. The two different reads were then compared, and the
otoliths on which the counts disagreed were reread and compared again. If there was still a deviation, a second reader counted and compared the annuli. If 100% agreement between the different annulus counts did not exist, then the otolith was removed from further analysis.The sulcal groove length (SGL) age estimation technique was used to estimate the age of fish with no annuli (< 1 yr; young-of-the-year(YOY)) and it relies upon a linear relationship between otolith growth and the growth of the fish in the first year of life (Francis 1995). These body length – otolith radius data are described as the population growth trajectory, which is critical in establishing proportionality between the fish and otolith growth in order to estimate the ages of YOY fish based on otolith measurements from adults (Francis 1995).Gauldie (1996) successfully used a similar technique to estimate ages of blue grenadier(Macruronus novaezelandiae), which he found to be strongly correlated to length modes observed in wild fish.