Influences of abiotic factors on the return, ocean abundance, and maturity of sockeye salmon (Oncorhynchus nerka) in the northern North Pacific Ocean

Abstract

The fluctuations in return, ocean abundance, and maturity of sockeye salmon (O. nerka) were examined and related to wind stress curl, sea suface temperature (SST), sea level pressure, and cloudiness, in the area between 40$\sp\circ$N-60$\sp\circ$N and 160$\sp\circ$E-140$\sp\circ$W. Historical records, during two periods, 1971-76 and 1955-86, were the primary source of data. Spectral analysis of a 360-month period of mean wind stress curl during 1955-85 showed 3.1- and 5.3-year cycles. The 5.3-year cycle was correlated (r =.32 to.44, P $<$.10) with the return of Bristol Bay sockeye salmon mostly at 0- (the year of spawning migration) and 1-year lag (the first year of lake residence). The relative ocean abundance of sockeye salmon in the northwestern Northern Pacific during 1971-76 was lowest during the three periods: 1961-70, 1971-76, and 1977-85. Mature Kamchatka sockeye salmon were 24% more abundant than mature Bristol Bay sockeye salmon during 1971-76. A significant relationship was found between the May-June mean SST and abundance of sockeye salmon (r =.56 to.66, P $<$.01) during 1961-85. In the northern North Pacific, the SST was positively (r =.73 to.86, P $<$.001) related with the gonad weight of sockeye salmon. The results indicated a close relation between the return, ocean abundance, and maturity of sockeye salmon and most of the abiotic factors.