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).