Coastal sea surface temperature and coho salmon production off the north-west United States

A time Series of mean weekly sea surface temperature (SST) images was used to investigate the relationship between fluctuations in the marine survival of hatchery-reared coho salmon and coastal ocean dynamics off the north-western United States (51 degrees to 37 degrees N) between 1985 and 1996, using univariate and nonlinear bivariate regression analysis. Ocean conditions were matched against survival for a number of different annual time frames according to the sum of negative or positive weekly SST anomalies. From the univariate analyses, the sum of negative anomalies from April to June, when the juvenile salmon first enter the ocean, was found to have an R-2 of 0.88 against survival with 1991 excluded as an outlier. The bivariate multiple regressions used the sum of negative anomalies from April to lune as the first independent variable. When the sums of positive anomalies from the following periods during the fishes' second calendar year in the ocean were each used as the second independent variable, the R-2 Values were all greater than or equal to 0.92 (with no data points excluded): January to June, February to lune, April to June, March to lune. These results are discussed within the context of coastal ocean processes. It is concluded that the analysis of SST image time series might allow management to make reasonable forecasts of hatchery-reared coho salmon survival.