Maturity at age of chub mackerel Scomber japonicus caught in the northwestern Pacific Ocean by China and Japan

Maturity rate at age of chub mackerel is examined by China and Japan. Quarterly maturity at age data is submitted from China and Yearly maturity at age data is submitted from Japan. Yearly maturity at age data from China is estimated using arithmetic mean of quarterly data. Chinese maturity at age data shows early maturation from 2018-2022 and Japanese maturity at age data shows late maturation at the concurrent years, however, also shows early maturation when the stock was scarce. The maturity at age data for the stock assessment requires discussion however it is recommended to use proxy values rather than highly variable number that changes on annual basis.