Aerial Surveys for Cetaceans in the Former Akutan, Alaska, Whaling Grounds

Randomized aerial surveys were flown between 26 July and 26 August 1984 to search for cetaceans in two areas of southwestern Alaska: one on both Bering Sea and Pacific Ocean sides of the Aleutian Islands near the defunct Akutan shore-whaling station, which operated from 1912 through 1939, the other overlapping continental slope and shallow continental shelf waters between the Aleutians and the Pribilof Islands. Surveys were made at altitudes between about 150 m and 245 m from a Partenavia P68 Observer with a plexiglassnose bubble, which permitted center-line viewing. Searches covered about 3940 nautical miles(nm),including some 2403 nm of random transects. Sightings were made of gray whales (10 sightings, 14 individuals), fin whales(3, 11),minke whales(1, 1),unidentified beakedwhales(1,6), Dall's porpoises(47, 131), killer whales(8, 26), and harbor porpoises(4, 7). A Fourier series model was used to estimate density of Dall's porpoises as 115 individuals(CV = 0.263)per 1000 nm² on the whaling grounds and 16.6 individuals(CV = 0.0)per 1000 nm² in the Bering Sea north of the whaling grounds. These estimates are comparable tothose previously reported for the general same general areas(97.2 animals per 1000 nm² ,SD = 49.5). There were too few sightings of other cetaceans to permit calculation of meaningful density estimates. At least four species of great whales(blue, fin, humpback andsperm) were sufficiently abundant during the first four decades of this century to support significant whaling activities within about 100 nm of Akutan(more than 5300 whales were caught during 23 years of whaling, 1912-39). Although previous studies of the fisheries showed a downward trend in catch per unit of effort and an increase in distance traveled to take whales, whales were still being taken at relatively high rates(0.28-0.51 whales per gross catcher day)at the end of the fishery in 1939. Populations of fin, humpback, blue and sperm whales were probably significantly reduced by shore and pelagic whaling conducted widely in the North Pacific since 1939. The low number of sightings on the present surveys probably means that populations on and near the whaling grounds remain depressed from such activities. /// Des relevés aériens ont été effectués au hasard entre le 26 juillet et le 26 août 1984, afin de déterminer la présence de cétacés dans deux régions du Sud-Ouest de l'Alaska: l'une située des deux côtés des îles Aléoutiennes(du côté de la mer de Bering et du côté de l'oc