Scientific Reports of the Whales Research Institute (1987)


Eighty nine mother-calf Dall’s porpoise pairs were sighted in August and September 1982, 1983 and 1985 in the Bering Sea and the western North Pacific (outside the principal range of the truei-type population). These sightings were analyzed with an attempt to determine the range of the calving ground and the identity of the stocks. Three discrete concentrations of such pairs were found in the study area, two in the Pacific area north of 45°N and another in the central Bering Sea. The dalli-type Dall’s porpoises in the surveyed area represent at least two local stocks each breeding to the north and south of the western Aleutian Islands. In addition to these, there is probably another stock which calves off the east coasts of the northern Kuril Islands, although its relationship with the Sea of Japan-Okhotsk Sea stock needs additional examination.