Age and growth of Pacific saury Cololabis saira (Brevoort) in the western North Pacific Ocean estimated from daily otolith growth increments

摘要

Growth of Pacific saury Cololabis saira (Brevoort) inhabiting the western North Pacific wasstudied based on counting daily growth increments with a scanning electron microscope (SEM). The small-size group (knob length: 200-240mm), medium-size group (knob length: 240-280mm) and largesize group (knob length: >280mm) showed increments of 256±26.0 (S. D.), 405±76.1 and 566±48.2, respectively. Based on daily growth increment formation, we determined that the ages of the 3 groups were about 8, 13, and 19 months. Small- and large-size fish were considered tohave been hatched from autumn to winter, and medium-size fish from spring to summer. The oldest specimen of Pacific saury examined in this study was about 23 months of age; thus, the lifespan of Pacific saury in this area seems to be at least 1.5 years.