Fluctuations of Pelagic Fish Populations in Relation to the Climate Shifts in the Far-East Regions

Based on a time series of ocean climate indices and catch records for seven pelagic fish speciesin the Tsushima Warm Current (TWC) and Kuroshio-Oyashio Current (KOC) regions from 1910 to 2004, wedetected regional synchrony in the long-term fluctuations of the fish populations and identified alternation patternsof dominant species related to climate shifts. The annual catches of Pacific herring, Japanese sardines,Japanese anchovies, jack mackerel, chub mackerel, Pacific saury and common squid in the TWC regionfluctuated in phase with those in the KOC region, which suggests that they were controlled by the samebasin-wide climate forcing. After the collapse of the herring fishery, the alternation sequence was: sardines(1930s), Pacific saury, jack mackerel, common squid and anchovies (1950s～1960s), herring (late 1960s～early1970s), chub mackerel (1970s) and then sardines (1980s). As sardine biomass decreased in the late stages ofthe cool regime, catch of the other four species increased immediately during the warm period of the 1990s.Regional differences in the amplitude of long-term catch fluctuations for the seven pelagic fishes could beexplained by regional differences in availability, fishing techniques and activity.