Size distribution of Pacific bluefin tuna caught with Japanese set nets estimated via the stratified stepwise weighting method

摘要

A stock assessment of Pacific bluefin tuna was conducted by stock synthesis; the representative size distribution of landed fish provided principal data for the assessment model. In this study, we stratified the catch and size distribution data collected from 24 prefectures on the coast and estimated the length or weight distribution of Pacific bluefin tuna caught with Japanese set nets via the stratified stepwise weighting method using a generalized linear model (GLM). The results indicated that approximately 60 of the set net catch of Pacific bluefin tuna in Japanese coastal waters were age-0 fish. However, older fish (age-1 fish) were mainly caught on the Pacific side of North Honshu and north of Aomori Prefecture during the summer and winter.