An aerial survey for sperm whales off the coast of Western Australia 1963-1965.

Abstract

Objectives, methods, and results of a two-year aerial survey for sperm whales off the coast of Western Australia, 1963-65, are described. Data from commercial whaling operations have been included where appropriate. Sperm whales were found well off the west coast, but only in a narrow strip along the continental slope off the south coast. On both coasts, the main direction of movement was parallel to the coastline and towards Cape Leeuwin. Unexpectedly, whales off the west coast were heading mainly southwards throughout the year. Densities in the offshore area north of Perth were significantly higher than along the continental slope in the same region but similar to those along the continental slope from Perth to Cape Leeuwin. The situation was reversed on the south coast with whales being found, in high densities, only along the continental slope. Off the west coast, there were marked decreases in abundance in winter, with peaks in spring-early summer and autumn; no change in direction of movement could be related to the peaks. Average numbers calculated as present in the survey area at one time were: west coast, c. 1000 whales; south coast, c. 200 whales. South coast data indicate the passage of about 40 whales in one 24 hr period, very similar to results from whaling company aerial spotter data off Albany. The hypothesis of two separate populations of sperm whales off Western Australia is discussed and thought to be unlikely. A small amount of data on baleen whale sightings is recorded.