Otolith Features and Reliability for Age-determination of Hoki Macruronus novaezelandidae (HECTOR) in Waters around New Zealand

Abstract

The otolith was composed of dark nucleus, light hyaline zones and dark opaque zones when observed in direct light. Pattern of otolith was divided into six types according to the clearness of the hyaline and opaque zones. The comparisons of frequency distribution of types were made and no difference was observed between the NORTHWEST region and the SOUTH region. How-ever, difference was found between the above two regions and the EAST region. The reliability of the otolith for age-determination was discussed. Although the readability varied with total length and otolith types. the corresponding rings showed regularity in positions. Also, the ring radius and the number of rings increased with total length and they are considered to be formed whith the growth of fish. Two independent readings of otolith agreed reasonably. Therefore, the otolith was thought to be usefulfor the age determination of individual fish.