Long-Term Changes in Fish Assemblage Structure in the Korea Strait from 1986 to 2010 in Relation with Climate Change

Climate change is expected to impact on marine-capture fisheries around the world. The Korea Strait showes the highest fisheries production among the adjacent seas of Korea, but studies on changes in the fish community related with climate change are scarce. We evaluated the spatio-temporal changes in fish assemblages, and their relationships with oceanic conditions in the Korea Strait (KS, 126°–129°5′E, 33°5′–35°N)  to provide a scientific basis for developing fisheries policies to adapt to climate change and global warming. We used the inflow indices of the Korea Strait Bottom Cold Water and the Tsushima Warm Current, water temperature and salinity, and commercial fisheries catch data from 1986 to 2010. To detect temporal shifts in the oceanic conditions, we applied a sequential t test of regime shift. To evaluate spatio-temporal changes of the fish assemblage structure by year, month, and fishing block, we graphically summarized the species compositions of the commercial fisheries catch data by correspondence analysis (CA). We conducted cross-correlation and canonical CA to evaluate the relationship between the oceanic conditions and fish assemblages. Sardine and filefish dominated in spring and were mainly distributed far away from the coast. Anchovy were mostly caught in summer near the southeast coast of Korea, and their annual catch steadily increased. Squid and hairtail dominated in autumn–winter, and were mainly distributed from the northern part off Jeju Island to the southeast water of Korea. Chub mackerel were relatively constant in annual and seasonal catch. CA detected a shift in the fish assemblage between 1990 and 1991, which we speculated was triggered by the 1988–1989 regime shift in the North Pacific. Surface temperatures at 0–20 m depths, especially with a time lag of 1 year, were significantly correlated with the 1990–1991 shift in fish assemblage structure. We concluded that (1) the KS is an intermediate area between the waters of Ieodo and the East Sea with respect to the timing of shift in fish assemblage structure, (2) the regional shifts were characterized by the replacement of dominant fish species from sardine and filefish to chub mackerel and squid. We hope that further multidisciplinary studies between regional oceanographers and fisheries scientists will contribute to the development of fisheries policies through better understanding of the interactions between oceanographic processes and fishes at the regional scale in adaptation to climate change.