2021 Volume 87 Issue 2 Pages 78-88
Regional variability in catches of the Japanese flounder Paralichthys olivaceus in Japanese waters was investigated. Catches of Japanese flounder from coastal prefectures from 1978 to 2017 were analyzed using principal component analysis. The first to sixth principal components were extracted to examine variability in catch among regions. Although the values increased and decreased at intervals of approximately 10 years, the first principal component showed an increasing trend over time. The first principal component was positively correlated with catches from northern and central Honshu on the Pacific coast, and Hokkaido. However, there was a negative correlation with catches from the Japan Sea. The second principal component was positively correlated with catches from the southern part of Japan on the Pacific coast, the Seto Inland Sea and the East China Sea, where water temperature was high, but was negatively correlated with the northern region of the Japan Sea. Correlations between the first and second principal component scores and catch of Japanese flounder varied among regions. Based on such variability, modification of the current boundaries for Japanese flounder stocks is recommended.
