the Beaufort Sea since 1974 (Figs. 24-27, 30, 31) indicate 

 that bowheads are distributed from shallow coastal waters to 

 the pack ice and perhaps into the pack ice. The numerous 

 sightings in shallow water from Point Barrow to Smith Bay 

 (Fig. 30) seem to confirm the importance of the nearshore 

 areas to this species in the western Beaufort Sea. 



From Point Barrow the animals appear to move westerly 

 to Herald Shoal and Herald and Wrangel Islands (Cook 

 1926; Townsend 1935; Bockstoce 1977), then south through 

 the Chukchi Sea into the Bering Sea. There is speculation by 

 Soviet scientists that bowheads pass to the Bering Sea by 

 traveling the western Chukchi Sea. Some animals appear to 

 move southwest along the northwest coast of Alaska past 

 Point Barrow to the Bering Strait, but this probably varies 

 with weather and ice conditions. Most in the population mi- 

 grate to the north side of the Chukotka Peninsula before 

 entering the Bering Sea (Fig. 2; Townsend 1935; Johnson et 

 al. 1981). Johnson et al. (1966) and F. Durham 26 believed 

 that the fall migration through the Chukchi Sea followed an 

 offshore passage, since bowheads were not seen at Wain- 

 wright, Cape Thompson, Point Hope, or Kivalina in the 

 autumn during their studies. Simultaneous sightings of bow- 

 heads in the eastern Beaufort and western Chukchi Seas sug- 

 gest that 1) there is a division in the autumn migration, with 

 some whales leaving the Beaufort Sea perhaps as early as 

 July and/or August; and/or 2) there are two subpopulations 

 (i.e., that a later component of the spring migration moves 

 into the Chukchi Sea and remains there in summer not com- 

 pleting the migration into the Beaufort Sea). Preliminary 

 data presented earlier and in Braham et al. (1980b) suggest 

 the first hypothesis is the more likely one. 



Bowheads generally enter the northern Bering Sea in No- 

 vember and December, although sometimes they are seen in 

 late September, arriving in central Bering Sea wintering areas 

 in December-February. 2 ' 



Life History and Associated Information 



Reproduction 



Facts about the reproductive biology of the bowhead whale 

 are scant, though information gathered on animals harvested 

 by Alaskan Eskimos has provided opportunities to study this 

 species' reproductive cycle. A summary of some estimated 

 reproductive life history data is reported in Table 2. 



Sexual maturity is reached when animals attain lengths ex- 

 ceeding 1,100 cm. Durham (1979, footnote 10) reported that 

 males attain sexual maturity at 1,158 cm (38 ft) and females 

 at 1,220 cm (40 ft) at 4 yr of age. Marquette (footnote 14) 

 noted that two female whales taken at Barrow, one accom- 

 panied by a newborn calf and the other containing a fetus, 

 measured 1,525 cm (50 ft) and 1,730 cm (56 ft 6 in) long, 

 respectively. From the presence of corpora albicantia in 

 ovaries of 12 whales harvested in 1978 and 1979, sexual ma- 

 turity in females may be reached at about 1,200 cm (pre- 

 liminary findings); and adult females are larger than males 

 (Johnson et al. 1981). Age, and length at first pregnancy, 

 however, are unknown. 



The mating period of the bowhead whale is not well known. 

 Durham (footnote 10) maintained that mating occurs in early 

 April before the whales reach Point Hope. Foote (footnote 

 21), however, observed what appeared to be copulatory be- 



"F. Durham, University of California, Los Angeles, Calif., pers. commun. 21 

 September 1978. 



"D. Harry and C. Oozeva. Gambell, Alaska, pers. commun. 25 July 1978 and 

 25 February 1979, respectively. 



157° 30T/V 156= 154' 



1 r~ 



150° 



i«r 



72° M 





BEAUFORT SEA 



Figure 30. — Bowhead whale sightings in Ihe Beaufort Sea, Augusl through November 1974-78. Only sightings with a verified position were used. Most sightings occurred 



in the last half of September. The dash line represents the 12 m depth contour. 



19 



