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° to 37°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 R2 of 0.88 against survival with 1991 excluded as an outlier. The bivariate multiple regressions used the sum of negative anomalies from April to June 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 R2 values were all greater than or equal to 0.92 (with no data points excluded): January to June, February to June, April to June, March to June. 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.

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The relationship between oceanographic conditions and clupeoid (pilchard, Sardinops sagax, and anchovy, Engraulis capensis) recruitment in the northern Benguela upwelling system was investigated from 1981 to 1987 using a time‐series of mean weekly SST images. Two approaches were taken. The first involved correlating recruitment success with the number of weekly coastal `SST events' above various cut‐off temperatures during the main reproductive season. The second involved constructing a multiple regression model of recruitment success with two independent environmental variables: namely, the number of coastal `SST events' greater than 19°C, and an onshore retention index for the early life‐history stages. The retention index was derived from a spatial time‐series analysis of the SST images using principal components analysis. In general, pilchard recruitment showed a positive relationship with the `number of SST events' whilst anchovy recruitment had a negative relationship; 1987 was an outlier year, during which there were exceptionally high levels of both pilchard and anchovy recruitment. The multiple regression R2 values were high and significant for both species (pilchard R2 = 0.88, anchovy R2 = 0.96). The regression model also accounted for the 1987 outlier according to levels of onshore retention which, despite low inshore SSTs, were particularly high during the 1986/87 reproductive season. Although these results need to be validated with data from a longer time period, they show how satellite data might be used for predicting clupeoid recruitment success in the northern Benguela.

The physical dynamics of the northern Benguela upwelling system between July 1981 and August 1987 were investigated by applying standardized Principal Components Analysis to a time-series of 235 mean, weekly sea surface temperature satellite images of the region. The first three principal components accounted for 87% of the total variance in the standardized input images and were the only components retained for interpretation. Principal Component I (PC I) represents the mean spatial structure of the system in terms of relative SST gradients, PC II represents the balance in dominance between inshore-offshore v. longshore SST gradients and PC III highlights patterns associated with the warming of the central Namibian region (19-23°5) in conjunction with the maintenance of cooler conditions to the north and/or south. These results are interpreted within the context of previous findings on the behaviour of the system, and their relevance to c1upeoid recruitment is discussed. Strong negative loadings on PC II indicated conditions which would promote the longshore "retention" of clupeoid eggs and larvae and "concentration" of planktonic food across thermoclines and thermal fronts, whereas strong positive loadings on PC III indicated conditions which would promote onshore retention and concentration. Conditions promoting onshore retention would, on occasion, have also been reflected by positive loadings on PC II whenever there was a uniform contraction of the offshore upwelling front, as a result of reduced, but similar, levels of upwelling along the entire coast.