Figure 7. First mode of an EOF analysis using SST averaged each year from January to June for 1968-1998. This mode explained 43% of the variance.
The feeding grounds of nine of the salmon stocks were located in the NE Pacific. We compared the averaged δ15N values of these stocks with δ15N values extracted from zooplankton isoscapes (Espinasse et al., in press) (Figure 8). The linear regression applied to these data gave an almost 1:1 coefficient with a Y intercept value of 4.6 (with zooplankton as TL=2). Assuming a trophic enrichment factor of 3.4‰, the trophic levels of the salmon stocks varied between 3.30 and 3.76 (Table 3).