Catch at length, age length key, and catch at age of chub mackerels Scomber japonicus caught in the northwestern Pacific Ocean by China, Japan, and Russia

Catch at length, age length key (ALK), and catch at age are analyzed and compared from China, Japan, and Russia. The details on the origin of the data and aging methods are explained. Submitted data from China and Japan use different timing for age incrementation, therefore, in this document, ages are converted based on July 1st as the origin of age incrementation. Catch at age is calculated that Chinese catch number is increasing since 2019 and Japanese and Russian catch numbers are decreasing since 2020. Chinese age composition shows majority of the Chinese catch is less than age-3 fish, and Japanese and Russian catch includes substantial amount of age 4+ fish. This paper recommends adopting Japanese ALKs for Chinese catch at age in 2016 and 2017 where Chinese ALKs are unavailable. This paper also recommends a scenario to estimate catch at age for 2015 for China and 2014-2015 for Russia from the 2016 catch at length data and corresponding Japanese ALK.