1980년대 기후체제변환과 동해 명태의 생물량 변동

Abstract

Walleye pollock (Gadus chalcogrammus, hereafter pollock) was one of the most dominant species in Korean waters in the late 1970s and early 1980s, but its biomass has decreased since the late 1980s and was completely collapsed in the early 2000s. Especially, in the late 1980s, the catch production of pollock in Korean waters were considerably decreased: for example, the catch production was declined by about 71 % from of 84,545 M/T in 1985 to 24,217 M/T in 1989. Such a considerable decrease has been attributed to overfishing and climate change, without concrete evidence. In this study, we investigated how the decrease in biomass of pollock was related to environmental changes in Korean waters using atmospheric data (air temperature and wind) from Korean Meteorological Administration and oceanographic data (sea surface temperature) from Korea Oceanographic Data Center). A CuSum analysis reveals that both sea surface temperature (SST) and atmospheric variables (air temperature and wind) show a regime shift in late 1980s when the pollock was significantly declined. The regime shift seems to be related with an increase in frequency of the sea surface temperature higher than 12℃ above which pollock larval survival rate may be considerably low. Our results suggest that climate changes, in addition to overfishing, could contribute to the stock collapse of pollock in the early 2000s.000s. Especially, in the late 1980s, the catch production of pollock in Korean waters were considerably decreased: for example, the catch production was declined by about 71 % from of 84,545 M/T in 1985 to 24,217 M/T in 1989. Such a considerable decrease has been attributed to overfishing and climate change, without concrete evidence. In this study, we investigated how the decrease in biomass of pollock was related to environmental changes in Korean waters using atmospheric data (air temperature and wind) from Korean Meteorological Administration and oceanographic data (sea surface temperature) from Korea Oceanographic Data Center). A CuSum analysis reveals that both sea surface temperature (SST) and atmospheric variables (air temperature and wind) show a regime shift in late 1980s when the pollock was significantly declined. The regime shift seems to be related with an increase in frequency of the sea surface temperature higher than 12℃ above which pollock larval survival rate may be considerably low. Our results suggest that climate changes, in addition to overfishing, could contribute to the stock collapse of pollock in the early 2000s.