Catch fluctuation of yellowtail species in relation to fluctuations in the geographical catch center

Abstract

Many studies reported that the catch of yellowtail species increased largely in the waters around northern Japan, particularly in the northern boundary of yellowtail distribution under the warm regime after 1990’s; whereas only a few studies focused on the catch in the water around Kagoshima, southwestern Japan and the southern boundary of the distribution. In this study, the catch fluctuations of yellowtail species in the water around Kagoshima have been analyzed and compared with those around Japan. We calculated the geographical center of yellowtail species catch and examined it’s relationships with regime shifts, sea surface temperature (SST) fluctuations, and catch fluctuations. The results indicate there was a significant negative correlation between the long-term fluctuations of catch in Kagoshima and Japan excluding Kagoshima (p<0.001), and the former increased (decreased) with the decrease (increase) in the latter with 4 years lag. It shows that the geographical center of the catch shifted northeastward with the increase in the SST in the mid latitudinal zone of Japan. The geographical center of the catch shifts southwestward (northeastward) in the cold (warm) regime, suggested that the fluctuations in the geographical center of the catch correspond well with regime shifts. Accordingly, the contrary trends in the catch between Japan and Kagoshima were interpreted as resulting from the changes in the distribution of yellowtail in responding to environmental SST fluctuations.