Using a Numerical Model of the Northeast Pacific Ocean to Study the Interannual Variability of the Fraser River Sockeye Salmon (Oncorhynchus nerka)

The hypothesis that numerical ocean circulation models could benefit fishery management was tested by first simulating the interannual variability of the northeast Pacific Ocean from 1955 to 1979 with the Bryan–Cox–Semtner ocean model (from the Geophysical Fluid Dynamics Laboratory, Princeton, NJ) and then relating the model output to the interannual variability found in the Fraser River sockeye salmon (Oncorhynchus nerka). Empirical orthogonal function (EOF) analysis was first used to condense the model output fields as well as the atmospheric forcing data. Next, the amplitude of the EOF's were regressed with the annual values of the sockeye variables (return migration route and timing, marine survival, and fork length) by stepwise multiple regression, with various time lags between the physical and the sockeye variables. The EOF modes associated with interannual variability (usually mode 2) were more often correlated with the sockeye variables than the other modes thought to contain mainly the seasonal cycle (mode 1) or else noise. The correlations between the physical variables and the sockeye variables were highest in the first and final few months of the sockeye marine life.