Using air-deployed passive sonobuoys to detect and locate critically endangered North Pacific right whales

摘要

The North Paci?c right whale (Eubalaena japonica, NPRW) is arguably the most endangered large whale in the world. Whaling records indicate that right whales were once abundant throughout the eastern North Paci?c and Bering Sea over the continental shelf, slope, and abyssal plain during the summer months (Clapham et al. 2004, Shelden et al. 2005). Recent mark-recapture estimates of abundance from both photographic and genotype data collected during dedicated cruises and opportunistic sightings in the southeastern Bering Sea (SEBS) indicate an eastern North Paci?c population of approximately 30 individuals, with an estimated eight females (Wade et al. 2011b). Although this may relate to a subpopulation, the paucity of sightings elsewhere indicates the entire eastern population is not likely much larger (Wade et al. 2011a, b). Marques et al. (2011) obtained comparable abundance results from passive acoustic studies and proposed these animals may belong to a subpopulation of the western stock, but there are insuf?cient data to support this hypothesis at this time. Such low numbers are in part a result of extensive historical whaling in the 19th century. Brownell et al. (2001) suggested that the population was growing by 1960, but large illegal catches by Soviet whalers totaling 529 animals 2 during the 1960s in the Gulf of Alaska and Bering Sea likely crippled recovery. Today, they are a remnant of their former population with a presumably restricted summertime range (Clapham et al. 2004). Although the eastern NPRW is listed as critically endangered (Reilly et al. 2008), current recovery efforts for this species are impeded by major gaps in knowledge regarding their population size, distribution, migration, habitat use, and anthropogenic threats.