the Beaufort Sea to the United States-Canadian border at 

 long. 141 °W. 



Sea ice covering the Chukchi Sea begins to advance south 

 in early October from its most northerly limit near lat. 72°- 

 74° N and extends well into the Bering Sea through June dur- 

 ing average ice years (Shapiro and Burns 1975). Sea ice is 

 present winter and spring over most of the intercontinental 

 shelf of the northern and eastern Bering Sea and occurs in- 

 frequently in the southwestern Bering Sea. With the progres- 

 sion of winter, landfast ice develops most extensively in bays 

 and inlets that are protected from the shearing forces of 

 mobile drift (sea) ice. Landfast ice increases outward from 

 shore to the 12-30 m depth contour. Along the northwest 

 coast of Alaska from Point Hope to Point Barrow in spring, 

 a persistent flaw or transition zone occurs between the land- 

 fast ice and pack ice where open water often is found. These 

 open water pathways are called leads when they are long and 

 thin; when the openings are persistent and lake-like, they are 

 called polynyas. The importance of polynyas has recently 

 been summarized by Stirling (1980). It is this transition zone 

 which is used by migrating bowhead and white whales. The 

 transition zone may exceed 50 km in width near Cape Lis- 

 burne and Point Hope during some years (pers. obs.; Burns 

 et al. 1977'); east of Point Barrow into the Beaufort Sea the 

 zone occurs farther offshore (Marko 1975). 



Shelf waters of the Beaufort Sea are typically ice-free from 

 late July to September or early October, but northernly winds 

 may keep or blow the pack ice near or against the coastline 

 at any time (Blood 1977 J ). 



Data Sources 



Aerial surveys were used to study the spatial distribution 

 of bowhead and white whales throughout the Bering, Chuk- 

 chi, and Beaufort Seas. Data collected during these surveys 

 have been digitized, stored in the National Marine Mammal 

 Laboratory computer file library (Appendix 1), and submitted 

 to the Environmental Data Service (EDS), NOAA. 



Spring migration and temporal distribution of bowhead 

 and white whales along the northwest coast of Alaska were 

 studied from ice and land stations near Point Barrow, Cape 

 Lisburne, and Point Hope. Since data collected at these field 

 sites during 1976 and 1977 were analyzed by hand (not digi- 

 tized for computer analysis), they were not submitted to EDS. 



METHODS AND MATERIALS 



Ice and Land Camps 



During the spring migration, counts of bowhead and white 

 whales were maintained on a 24-h basis as conditions allowed 

 at the following localities: Fast ice edge near Point Barrow 

 (25 April-2 June 1976 and 19 April-3 June 1977); cliffs at 



Cape Lisburne (6-15 May 1977); and fast-ice edge off Point 

 Hope (18 April-28 May 1977). One or two observers stood 

 4-h watches. 



As whales moved past observers, the following informa- 

 tion was scored: Number of animals; direction of travel; 

 general behavior; weather conditions; time of day; and, when 

 possible, length of time animal(s) spent at the surface and 

 duration of dive. 



In 1978, an upgraded counting effort was conducted at 

 Point Barrow, Alaska, using two counting stations (Braham 

 et al. 1979). The camps, called South Camp and North Camp, 

 worked with each other, 15 April-5 June. South Camp ob- 

 servers made the primary counts and, through radio com- 

 munication to North Camp, North Camp observers evaluated 

 South Camp's results. The watch schedule during 1978 was 

 two observers per shift rotating each 3 h. Documentation of 

 current ice camp counting procedures and theory is reported 

 in Krogman et al. (1979) s and Krogman (1980). In addition 

 to the Barrow counts, counting was conducted at Cape Lis- 

 burne 2 April-7 June 1978. 



Aerial Survey 



Aerial survey procedures were designed to delineate near- 

 shore and offshore distribution of whales, frequently over 

 pack ice conditions. We flew the aircraft over open water — 

 the leads or polynya— at elevations of 70-300 m depending 

 upon cloud cover. Data collected on bowheads and white 

 whales during OCSEAP studies RU 14 (Krogman et al. 1979 6 ) 

 and RU 67 (Braham et al. 7 ) are included in this report. Aerial 

 survey methodology for RU's 14 and 67 differed in the place- 

 ment of flight tracks in that for those studies (walruses and 

 seals) tracks were flown as straight lines irrespective of sea ice 

 coverage. Because this report presents aerial survey results by 

 showing only tracklines and geographic positions of sightings, 

 the two methodologies of aerial survey (systematic flying 

 over open water versus straight tracklines) are analytically 

 equivalent although no estimate of abundance is generated 

 from either method. Aerial surveys were not flown to make 

 estimates of bowhead abundance. This method was deter- 

 mined to be impractical (experimentally) and too costly. 



Four aircraft types were used during the surveys for whale 

 distribution: A single engine Cessna from Cape Smythe Air 

 Service, Barrow, Alaska; a twin-engine Grumman Otter char- 

 tered from the Naval Arctic Research Laboratory, Barrow, 

 or Cape Smythe Air Service; a twin-engine Grumman Goose 

 and a Lockheed P-2V both chartered from the Office of Air- 

 craft Services, U.S. Fish and Wildlife Service, Anchorage, 

 Alaska. Depending on the aircraft used, one to five observers 



'Burns, J. J., L. H. Shapiro, and F. H. Fay. 1977. The relationships of marine 

 mamma! distributions, densities, and activities to sea ice conditions. In Environ- 

 mental assessment of the Alaskan continental shelf, annual reports of principal 

 investigators for the year ending March 1977, Vol. 1, Receptors mammals. 

 Unpubl. rep., p. 503-554. U.S. Dep. Commer., Natl. Oceanic Atmos. Admin., 

 Environ. Res. Lab., Boulder, Colo. 



'Blood, D. A. 1977. Birds and marine mammals: the Beaufort Sea and the 

 search for oil. Unpubl. rep., 12 p. Beaufort Sea Project, Dep. Fish. Environ., 

 Can. 



'Krogman, B. D.. R. M. Sonntag, H. W. Braham. S. Savage, and G. W. 

 Priebe. 1979. Arctic Whale Task ice camp survey format 1979 version. Unpubl. 

 manuscr.. 60 p. Natl. Mar. Mammal Lab., Natl. Mar. Fish. Serv., NOAA, 7600 

 Sand Point Way NE., Bldg. 32, Seattle, WA 981 15. 



"Krogman, B. D., H. W. Braham, R. M. Sonntag, and R. G. Punsly. 1979. 

 Early spring distribution, density and abundance of the Pacific walrus {Odo- 

 benus rosmarus) in 1976. Unpubl. rep., 47 p. Natl. Mar. Mammal Lab., Natl. 

 Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE., Bldg. 32, Seattle, WA 

 98115. 



'Braham, Ft. W., R. D. Everitt, B. D. Krogman. D. J. Rugh, and D. E. With- 

 row. 1977. Marine mammals of the Bering Sea: Preliminary analysis of distribu- 

 tion and abundance, 1975-76. Processed rep., 90 p. Natl. Mar. Mammal Lab., 

 Northwest and Alaska Fish. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand 

 Point Way NE., Bldg. 32, Seattle, WA 98115. 



