Ages Estimated from Average Microincrement Width in Otoliths of Macruronus Novaezelandiae are Verified by Length Mode Progressions

The sagittal otolith of Macruronus novaezelandiae (Merlucciidae: Teleostei) has a well developed prismatic structure, An age estimation technique was developed based on microincrement width along the longest nucleus-to-dorsal-prism growth axis, A training set of 31 otoliths was measured at intervals from four to eight times along this growth axis to generate an average microincrement width. Each measurement was the average width of 20 contiguous microincrements. The subsequent relationship between average microincrement width and the length of the otolith growth axis was used to estimate ages from 105 otoliths by measuring growth axis length and dividing by the expected average microincrement width. Annual length modes predicted by this age estimation method were strongly correlated with length modes observed in the fishery for M. novaezelandiae.