Age-determination and age-length keys for Pacific saury, Cololabisa saira, in 2019 and 2020

The age determination by the observations of otolith annual ring of Pacific saury, Cololabisa saira, collected in 2019 and 2020 was conducted. Annual, seasonal and monthly proportions of ages 0 and 1 fish were calculated at each 1-cm body length class. Although the body length distributions for 2019 showed obvious bimodal shape corresponding to ages 0 and 1 fish, the distribution for August to December 2020 could not be visually separated due to the smaller difference in the body lengths at peaks among the ages than the previous year. These results strongly suggest that the age determination technique using otolith is effective to estimate the accurate catch number at age of Pacific saury for years like 2020, when no clear difference is observed in the body lengths among the age.