Aerial Surveys of Bowhead Whales, North Slope, Alaska

During 1979 fall aerial surveys (August, September, and October), 134 individual or group sightings of bowhead whales were made in an area ranging from Point Barrow to Demarcation Bay along the North Slope of Alaska and primarily along the 10-fathom line. Of the 249 bowhead whales sighted, one group of six was observed inside the oil lease area near Narwhal Island, and 84 were seen to the north and outsided the oil lease area along the 10-fathom line. No bowhead whales were seen in or about the lease area during the spring (April-May) or the summer (June-July). Behavioral observations and statistical analysis of initial whale headings indicate that the majority of bowhead whales seen during August, September, and October were migrating in an unhurried manner. They were observed heading in many directions, with estimated speeds of 1.0 knot or less and were possibly feeding along the way. Thirteen tapes containing bowhead whale vocalizations of a quality suitable for analysis were recorded. Preliminary analysis indicates that the sounds are of a slightly higher frequency in the fall. The average overall frequency ranges of the spring and fall sounds were 30 to 2000 Hz and 30 to 3500 Hz, respectively. The peak migration began within an 11-day period between 27 September and 7 October 1979, and continued until 17 October 1979. The total numbers of whales traveling through the survey area were estimated (within 95% confidence limits) to be 852 + or - 533 for a 21-day migratory period and 1620 + or - 1051 for an 11-day period.