Summer and winter whales in the Pacific Arctic

Abstract

Changes in sea ice phenology have been profound in the Pacific Arctic, where the seasonal open-water period has increased by ~1.5 months over the past 30 years. The greatest changes in the open water season have occurred in fall resulting in changes to the Arctic ecosystem, including increased primary productivity, changing food web structure, and opening of new habitat. In the “new normal” Arctic, sub-arctic “summer” whales (fin, humpback, and killer) are poised to inhabit new seasonally ice-free habitats in the Arctic. The spatial and seasonal occurrence of summer and “winter” (bowhead) whales over 5 years from September through December was examined by deploying hydrophones in Bering Strait and comparing acoustic occurrence of the species concomitant with decadal-scale changes in seasonal sea ice. Fin and humpback whale acoustic detections extended from summer to late autumn while killer whale detections were more sporadic. Inter-annual differences in acoustic detections appear to be driven by interannual differences in the environment. Bowhead whale detections generally began after the departure of the summer whales and continued through the winter. In a future with further seasonal sea ice reductions, however, increased competition for resources between sub-Arctic and Arctic species may arise to the detriment of winter whales.