Long-term variability in the abundance of Pacific saury in the northwestern Pacific Ocean and climate changes during the last century

摘要

Long-term variability in the abundance of Pacific saury (Cololabis saira) in the northwestern Pacific was examined using catch data during 20th century. SOI (Southern Oscillation Index). NPI (North Pacific Index) and MOI (Monsoon index) were used asclimate indices to examine effects of climate changes on the abundance of Pacific saury. Abundance indices of saury both in weight and in number exhibit decadal variations with large interannual fluctuations, suggesting effects of long-term climate changes on saury. Power spectral analysis showed that the abundance of saury has cycles around 4-1 and 16-17 years, tending to respond to decadal scale variations in atmospheric-ocean systems in the North Pacific. Significant negative correlations were foundbetween the abundance index of large size group saury and SOI, indicating that El Nino-Southern Oscillation (ENSO) have marked impacts on the saury. MOI also showed high correlation with abundance index of large size group saury, indicating winter monsoonaffects the abundance of saury. Linkages between sea surface temperature (SSTs) and SOL and between SSTs and MOI demonstrated that the large size group saury is directly forced by the SST fields through large-scale climate/oceanic interactions. Whereasthere is no evident relationship between NPI and large group saury, abundance index of medium size group saury is significantly correlated with NPI, indicating that Aleutian Low maybe affect medium size group saury in decadal scale. Interannual and decadal variations in the abundance of saury seemed to respond to ENSO and oceanic regime shifts, respectively. It is important to determine decadal-interdecadal oceanic/climate changes in understanding the mechanism of fluctuation in the abundance of Pacificsaury.