Climatic regime shifts and their impacts on marine ecosystem and fisheriesresources in Korean waters

There were climatic regime shifts over the North Pacific in 1976 and 1988 w hich affected the dynamics of the marine ecosystem and fisheries resources in Korean waters. Precipitation in Korean waters showed a decadal scale cli matic jump, especially of Ullungdo Island, reflecting the regime shift that occurred in the North Pacific. The variation was also detected in East Asi an atmospheric systems. The Aleutian Low and North Pacific High Pressure Sy stems showed substantial changes in 1976 and around 1987-89. 1976 was an un usually warm year for Korea; mean sea surface temperature (SST) was higher than 'normal' and was accompanied by a northward shift in the thermal front . Post 1976, the: volume transport of the Kuroshio Current increased and hi gher seawater and air temperatures persisted until 1988. Other shifts occur red after 1976 such as an increase in mixed layer depth (MLD) and biologica l changes in the ecosystem of Korean waters including decreases in spring p rimary production and an increase in autumn primary production. Primary pro duction increased again after 1988, and was followed by a significant incre ase in zooplankton biomass after 1991. The 1976 regime shift was manifested by a decreased biomass and production of saury, but an increase in biomass and production of sardine and filefish in Korean waters. After 1988, recru itment, biomass, and production of sardine collapsed while those of mackere l substantially increased. Based on these observations, hypotheses on the r elationship between the climate-driven oceanic changes and changes in fishe ries resources were developed and are discussed. (C) 2000 Published by Else vier Science Ltd.