The estimated feeding grounds for stocks with spawning grounds south of the Aleutian Islands were all located in the NE Pacific itself but with little overlap between the stocks (Figure 4). The SE Alaska stocks Chilkat and Chilkoot, which have spawning grounds 10 km away from each other, showed well separated at-sea locations, with Chilkoot being distributed 10 degrees further west than Chilkat. While Columbia River stocks have the most southerly spawning grounds, their high seas distributions were located in the northern sector of the NE Pacific. The Rivers Inlet stock was distributed further south than any other stock. With the exception of Rivers Inlet, all stocks were sampled yearly and produced significant correlations with highest significance usually found using the original time series (Table 2, correlation coefficients were usually higher with smoothed time series but the adjusted degrees of freedom reduced the
Figure 4. Estimated feeding grounds during the last year at sea of (a) Red lake, (b) Upper station, (c) Chilkoot, (d) Chilkat, (e) Okanagan, (f) Wenachee and (g) Rivers inlet sockeye salmon stocks (Gulf of Alaska). Strongest correlation coefficient between SST and δ13C value is indicated by a white cross. Locations of the point of entry in the freshwater system of the different stocks is shown (red circle).
significance, see Methods). Bristol Bay stocks at-sea distributions showed interesting patterns with some stocks being distributed in the Bering Sea and some others along the Aleutian Islands (Figure 5).