Bowhead whale (Balaena mysticetus)
This contribution was not updated in 2011 and was therefore not included in the final text version of the "Ecosystem Considerations for 2012" report. It is provided here for informational purposes. Figure and table numbers correspond to the Ecosystem Considerations report in which it was included (see date of last update) located on the Stock Assessment Archives Webpage

Bowhead whale (Balaena mysticetus)

Contributed by Marcia Muto, National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA

Contact: marcia.muto@noaa.gov

Last updated: August 2010

All stocks of bowhead whales (Balaena mysticetus) were severely depleted by commercial whaling (Woodby and Botkin, 1993) and were classified as protected by the International Whaling Commission (IWC) under the 1946 International Convention for the Regulation of Whaling. The IWC currently recognizes the Okhotsk Sea, Spitsbergen, Eastern Canada-West Greenland, and Western Arctic stocks of bowhead whales (IWC, 2007b). The Western Arctic stock, also known as the Bering Sea (Burns et al., 1993) or Bering-Chukchi-Beaufort Seas (Rugh et al., 2003) stock, is the only stock of bowheads in U.S. waters (Rugh et al., 2003; George et al., 2007; IWC, 2007b). In the U.S., this stock is classified as endangered under the Endangered Species Act (ESA) of 1973 and depleted under the Marine Mammal Protection Act of 1972; thus, it is also considered a strategic stock. However, the Western Arctic stock has been increasing in recent years (George et al., 2004; Koski et al., In Press) and may be approaching its carrying capacity (Brandon and Wade, 2006).

Western Arctic bowheads generally migrate between wintering areas in the Bering Sea and summering areas in the eastern Beaufort Sea (Braham et al., 1980; Moore and Reeves, 1993). Systematic ice-based visual counts during this migration have been conducted since 1978 (Krogman et al., 1989; George et al., 2004). A summary of the resulting abundance estimates, corrected for whales missed during the census (Zeh et al., 1993; Clark et al., 1996), is provided in Table 11 (Allen and Angliss, 2010) and Figure 74 (George et al., 2004); however, these estimates have not been corrected for a small, unknown portion of the population that does not migrate past Point Barrow during the survey (Allen and Angliss, 2010). The most recent population abundance estimate in 2004 of 12,631 (CV=0.2442) whales in the Western Arctic stock (excluding calves) was calculated from aerial photographic surveys of bowhead whales in 2003, 2004, and 2005 (Koski et al., In Press). The rate of increase indicates a steady recovery of the stock (George et al., 2004; Brandon and Wade, 2006; Koski et al., In Press).

Table 11: (from Allen and Angliss (2010)). Summary of population abundance estimates for the Western Arctic stock of bowhead whales. The historical estimates were made by back-projecting using a simple recruitment model. All other estimates were developed by corrected ice-based census counts. Historical estimates are from Woodby and Botkin (1993); 1978-2001 estimates are from George et al. (2004) and Zeh and Punt (2004).

Year

Abundance Estimate (CV)

Historical estimate

10,400-23,000

End of commerical whaling

1,000-3,000

1978

4,765 (0.305)

1980

3,885 (0.343)

1981

4,467 (0.273)

1982

7,395 (0.281)

1983

6,573 (0.345)

1985

5,762 (0.253)

1986

8,917 (0.215)

1987

5,298 (0.327)

1988

6,928 (0.120)

1993

8,167 (0.017)

2001

10,545 (0.128)

Figure 74: (George et al., 2004). Population abundance estimates for the Western Arctic stock of bowhead whales, 1977-2001, as computed from ice-based counts, acoustic locations, and aerial transect data collected during bowhead whale spring migrations past Barrow, Alaska. Error bars show +/- 1 standard error.

There are no observer program records of bowhead whale mortality incidental to commercial fisheries in Alaska. Historically, however, some bowheads have had interactions with crab pot gear. More recent NMFS Alaska Region stranding records have reported bowhead whale entanglements, including a bowhead that was found dead in Bristol Bay in 2003, with line (of unknown origin) around its caudal peduncle and both flippers, and a bowhead that was observed near Point Barrow in 2004 with fishing net and line around its head (Allen and Angliss, 2010).

Alaska Natives living in villages along the migration route of the Western Arctic stock of bowheads have hunted these whales for at least 2,000 years (Marquette and Bockstoce, 1980; Stoker and Krupnik, 1993), and the IWC has regulated subsistence takes since 1977 (IWC, 1978). Alaska Native subsistence hunters landed 832 bowhead whales between 1974 and 2003 (Suydam and George, 2004), 37 in 2004 (Suydam et al., 2005, 2006), 55 in 2005 (Suydam et al., 2006), 31 in 2006 (Suydam et al., 2007), 41 in 2007 (Suydam et al., 2008), and 38 in 2008 (Suydam et al., 2009). Russian subsistence hunters harvested one bowhead whale in 1999 and one in 2000 (IWC, 2002), three in 2003 (Borodin, 2004), one in 2004 (Borodin, 2005), two in 2005 (IWC, 2007b), and two in 2008 (IWC, 2010). Canadian Natives also harvested one bowhead whale in 1991 and one in 1996 (Allen and Angliss, 2010). At its annual meeting in 2007, the IWC renewed the existing 5-year bowhead quota for the 5-year period from 2008 to 2012 (IWC, 2007a); the quota currently includes up to 280 whales landed, with no more than 67 whales struck in any year and up to 15 unused strikes carried over each year.

Oil and gas development in the Arctic has the potential to impact bowheads through increased risks of exposure to pollution and to the sound produced by exploration, drilling operations, and increased vessel traffic in the area (Allen and Angliss, 2010). Past studies have indicated that bowheads are sensitive to sounds from seismic surveys and drilling operations (Richardson and Malme, 1993; Richardson, 1995; Davies, 1997) and will avoid the vicinity of active seismic operations (Miller et al., 1999), active drilling operations (Schick and Urban, 2000), and the resulting vessel traffic (Richardson et al., 2004). Each year since 1979, the U.S. Department of the Interior’s Minerals Management Service (MMS) has funded and/or conducted aerial surveys of bowhead whales during their fall migration through the western Beaufort Sea in what is known as the Bowhead Whale Aerial Survey Project (BWASP). In 2007, as part of an Inter-Agency Agreement (IAA) between the MMS and NMFS, the National Marine Mammal Laboratory (NMML) took over the coordination of BWASP. Through a second IAA, the survey area has been expanded to include the northeastern Chukchi Sea as part of the Chukchi Offshore Monitoring in Drilling Area (COMIDA) project. To facilitate mitigation of future oil and gas development along the migration route of the Western Arctic stock of bowheads, the multi-year (2007-2012) Bowhead Whale Feeding Ecology Study (BOWFEST), administered by NMFS and funded by the MMS, will estimate relationships among bowhead whale prey, oceanographic conditions, and bowhead whale feeding behavior in the western Beaufort Sea (Rugh, 2009). Aerial survey daily reports for the BWASP, COMIDA, and BOWFEST projects are available at http://www.afsc.noaa.gov/nmml/cetacean/bwasp/index.php and annual reports are available through NMML.





   
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