Effect of climate-ocean changes on the abundance of Pacific saury.

Effects of ocean climate changes on the population structure and abundance of Pacific saury (Cololabis sira) were investigated on the basis of climate indices, sea surface temperature (SST) anomalies, catch and body size information from the Tsushima Warm Current (TWC) region (Yellow Sea, East China Sea and East/Japan Sea) during the period 1950-2010. It is suggested that oceanic regime shifts in the early 1970s, late 1980s and late 1990s occurred in the TWC region in winter, but the regime shifts in the mid-1970s and in the late 1980s were not evident in the spring SST anomaly series. The abundance and body size of Pacific saury fluctuated in association with the winter oceanic changes in the TWC region. The catch rates and abundance of large size saury were far bellow average during their northward migrations in the TWC region in the years with abnormally cool winters (e.g., 1963, 1970, 1977, 1981-1989 and 2006) and above average in the years with warm winters. These patterns demonstrate decadal-scale variations together with large inter-annual fluctuations in the structure and abundance of Pacific saury in association with the climatic-oceanic changes. These results, along with an alternation of dominant pelagic fish species, indicate the status of the saury population in the TWC region is in good condition, similar to that in the Kuroshio-Oyashio Current (KOC) region during the warm regime after the late 1980s climate regime shift.

Fluctuations in abundance of common squid, Todarodes pacificus in the Far East.

Long term fluctuations in the abundance of common squid, Todarodes pacificus are taken in the waters around Korea and Japan from 1952 to 2003. The year-to-year fluctuations in the abundance in the Tsushima Warm current (TWC) region (Yellow sea- east China sea-east/Japan sea) revealed the same pattern with that in the Kuroshio-Oyashio Current (KOC) region (Northern Pacific) except for the period of fishing shifts from the KOC to TWC region in the late 1960s and 1970s. Two period of high abundance in the entire fishing regions emerged in the 1950s-1960s and 1990s, in-between there has been a low level in the KOC region for 20-years (1970s-1980s) and in the TWC region for 10-years (1980s). The squid fishery in the marginal zone of the distribution range (KOC region) was mainly based on winter-breed microcohort that collapsed earlier (from the early 1970s) than that of the fishery in the central zone (TWC region), based on autumn and winter-breed microcohorts from the mid 1970s. During the low abundance period (1980s) the catch rates of the autumn microcohort were higher than those of the winter microcohort, while the abundance of the two increased schynchronously from the early 1990, suggesting the possible homogeneity of the population structure during the high abundance period.