Acoustic Detection of the Critically Endangered North Pacific Right Whale in the Northern Bering Sea

The eastern population of the North Pacific right whale (hereafter NPRW; Eubalaena japonica) is one of the most endangered baleen whale populations in the world (Reilly et al. 2008), numbering in the tens of individuals (n ≈ 30; Wade et al. 2011) due to historical whaling (19th and 20th centuries) followed by illegal catches in the 1960s (Scarff 2001, Ivashchenko and Clapham 2012, Ivashchenko et al. 2017). Whaling logs indicate that the majority of NPRW catches and sightings within the eastern Bering Sea (east of 175º W) ranged from the Aleutian Islands to St. Matthew Island, with limited (n<20) detections farther north (Fig. 1; Nasu 1960, Shelden et al. 2005). It has been suggested that at least some of the northern range historical sightings were either misidentified as bowhead whales (Balaena mysticetus) or were the result of transcription errors (Scarff 1986, Reeves et al. 2004). Yet, these northern detections were made over a large expanse of time (1834–1982) by observers of different nations, and included some sightings that were made on a dedicated research survey for endangered species (Brueggeman et al. 1984), thereby adding credence to the belief that NPRWs have occupied the northern Bering Sea in the past. Furthermore, Alaska Native whalers who hunt bowhead whales off St. Lawrence Island have on occasion observed right whales in the area, although details of such sightings are not available.