Possible Effects of the Sitka Eddy on Sockeye (Oncorhynchus nerka) and Pink Salmon (Oncorhynchus gorbuscha) Migration off Southeast Alaska

Abstract

The interannual variability of sockeye (Oncorhynchus nerka) and pink salmon (Oncorhynchus gorbuscha) catches during 1952–62 from southeast Alaska and northern British Columbia is examined in relation to the appearance and disappearance of the Sitka eddy in the offshore oceanic circulation. In years when this large (~300 km in diameter) and intense (surface currents ~0.5 m/s) vortex is present, the spawning migration routes of salmon returning to the Nass and Skeena rivers tend to be deflected southward. An analysis of salmon tagging data collected during 1957 (when the eddy was absent) and 1958 (when the eddy was present) supports this conclusion. The southward deflection during 1958 is a particularly interesting result in light of many other observations which show that several fish species were displaced northward during the 1958 warming of the northeast Pacific Ocean.