FIELD RESEARCH RESULTS 



Spring Counts of Migrating Bowhead Whales: 

 Ice and Land Camps 



Barrow 



Counts of bowhead whales were made 25 April-2 June 1976, 

 19 April-3 June 1977, and 15 April-5 June 1978 at the near- 

 shore lead northwest of Point Barrow. These periods coincided 

 with the annual northeasterly spring migration of bowhead 

 whales from their winter grounds in the Bering Sea to summer 

 feeding grounds in the Arctic Ocean. Summary data for these 

 three census years are presented in Table 1. The estimate of the 

 number of whales passing the camps during the census periods 

 was not, for 1976 to 1978, considered to be a total population 

 estimate. A more detailed comparison of indices among years 

 for the period 15 April-30 May is reported in Braham et al. 

 (1979, 1980c) and Krogman (1980). 



Table 1. — Summary of spring counts of bowhead whales during their annual 

 spring migration through the flaw zone near Barrow. Alaska. Indices of abund- 

 ance ("Index") were computed as the sums of the products of daily rates times 

 24 h (see Krogman 1980 and Fig. 3). 



Year 



Counting 

 period 



Total 

 hours in 

 period 



Total Percent 



hours period 



watched watched 



Bowheads 



counted 



Index 



1976 25Apr.-2June 936 392:25 42 330 762 



1977 19 Apr. -3 June 1,104 395:12 36 327 715 



1978 15 Apr. -5 June 1,248 1.108:44 89 1,389 '2,276 



In Braham et al. (1979) an estimate of 2,264 was given for the period from 15 

 April to 30 May. The value of 2,276 has a range of uncertainty of approximately 

 (-481 to +601) around the value, and will be further adjusted as results of bias 

 analysis dictate. 



The 1978 estimate of 2,276 was higher than indices of 762 

 achieved in 1976 (revised from 796, originally quoted in 

 Braham and Krogman footnote 2), and 715 in 1977 (Fig. 3). 

 The increase in counts is attributable to several factors: 1) In- 

 crease in survey effort (period of watch); 2) better survey 

 location; 3) environmental conditions; and 4) increase in ob- 

 server effort. 



Figure 4 partially illustrates the increase in survey effort by 

 comparing the number of hours watched per day during the 

 same time frame among years. These histograms illustrate the 

 variation in watch effort among years. For all years the stra- 

 tegy was to maintain an unbroken 24-h watch schedule. In 

 1976 and 1977, the period of OCSEAP funding, this watch- 

 effort strategy was undermined by fog, closed leads, unstable 

 ice conditions, and a limited number of observers. This was 

 not so during 1978, the first year of the NOAA, NMFS ex- 

 panded bowhead research program. 



In addition to the outstanding environmental conditions in 

 1978, another factor contributing to the increase in the esti- 

 mate was a change in location of the ice camps. During 1976 

 and 1977 the primary location for counting was 10-20 km to 

 the southwest of Point Barrow, where our observers stationed 

 themselves near Eskimo whalers. In that vicinity, the lead is 

 generally 11-32 km in width, whereas immediately northwest 

 of Point Barrow, where the 1978 camps were located, the 

 lead width is generallv 1-11 km wide. Durina 1978 the lead 



250- 

 200- 



150- 

 100- 

 50- 



1976 



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250- 

 200- 

 150- 

 100- 

 50- 



1977 



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 200- 

 150- 



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1978 



50- 



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 | APRIL 1 MAY 1 



Figure 3. — Comparison among years (1976-78) of estimated total number of 

 bowhead whales migrating northwardly past Pt. Barrow, Alaska, from 15 April 

 to 30 May. For purposes of comparison, totals are based on hourly rates per day 

 times 24 h. 



was open wider than 0.5 km approximately 94% of the time 

 providing us with an unusually long time period to watch for 

 whales. The median as well as mean (of means) lead width, 

 23 April to 1 June 1978, at Barrow as 3.70 km (SD = 2.94, 

 n = 38) as calculated from data in Brueggeman (1980). A 

 lead width of 5 km or less is considered ideal for viewing 

 bowheads. 



Another important factor contributing to a higher count 

 during 1978 was the increase in observer effort. The 1978 ob- 

 server schedule called for two observers per 3-h rotating 

 watch; in previous years single observers rotated every 4 h. 



Observers at South Camp conducted all watches from an 

 unusually high perch (ice ridge) in 1978. Height of the eye at 

 South Camp was approximately 11.8 m above sea level yield- 

 ing a view to the horizon of 10 km. Observers in 1976 and 

 1977 were located on young ice with eye height of 2-4 m, 

 vieldina a view to the horizon of 4-6 km. 



