Contemporary distribution of the eastern North Pacific right whale in the Bering Sea

Abstract

The eastern population of the critically endangered North Pacific right whale (NPRW; Eubalaena japonica) historically ranged in the eastern Bering Sea from the Aleutian Islands to St. Matthew Island (60.4°N), with limited (n < 20) detections further north (which some consider bowhead whale; Balaena mysticetus). Since the 1980s, most NPRW sightings have been isolated to the southeastern Bering Sea. In order to describe the current spatio-temporal distribution of NPRW, long-term passive acoustic recorders throughout the Bering Sea (2012–2016) were analyzed manually (10,204.2 days; 27–29% duty cycle) for the presence of NPRW, which were identified using the “up” and “gunshot” calls. NPRW were consistently detected during ice-free months in the southeastern Bering Sea, and intermittently during the same months northward to 59°N. NPRW were also detected at low calling activity within two eastern Aleutian Passes. Notably, NPRW were detected north of St. Matthew (61.6°N) in summer 2016 (July–Aug.). Up and gunshot calls north of 62°N in ice-free months and north of 58°N in ice-associated months could not be distinguished from bowhead whale. Together, these results indicate that NPRW currently range with certainty from the eastern Aleutian Passes to 61.6°N, but may range as far north as the Bering Strait.