Estimation of catch-at-size/age data of Pacific saury using stratified random sampling with proportional allocation

Pacific saury is immediately graded into several commercial size categories (by weight) on board in the saury far sea fishery, e.g., the Chinese Taipei saury fishery (CTSF). In this study, a stratified random sampling approach with proportional allocation was employed to refine the estimator of the catch-at-size/age data for the CTSF. We increased the sample size of saury length from ~300-500 per year in 2007-2019 to 2,492 in 2020, amounting to an approximately 5-fold increase, particularly for the abundant categories. Two sample fishing vessels with their own specifications of commercial size categories were employed to involved the potential monthly and/or between-vessel variation. In addition, both age-length keys for saury from Chinese Taipei and Japan were used to estimate the catch-at-age data. The age-0 and age-1 saury accounted for 63.3 % and 36.7 % of the 2020 CTSF catch, respectively. The mean percentage of age-1 fish in the 1o x 1o grids was greater than 91% in June and July, decreased to about 39-47% from August to October, and was less than 29% in November and December.