Distribution of Soviet catches of sperm whales Physeter macrocephalus in the North Pacific

From 1948 to 1979, the USSR conducted extensive illegal whaling worldwide. Data from the North Pacific (NP) were analyzed to correct falsified International Whaling Commission catch records and to investigate the distribution of sperm whales Physeter macrocephalus (NP catch = 157 680). Information was available on the distribution of 123 264 sperm whale catches. Among a number of areas defined by the Soviet whalers, the largest catches were in the 3 main regions: 31 395 in the Eastern Region (ER), 29 518 in the Central Region (CR), and 19 313 in the Western Region (WR); an additional 23 090 catches were made at the Kuril land stations. Other areas with substantial catches included the Aleutians (5945) and Commander Islands (1448), the Bering Sea (3170), Olyutorsky Bay (3094), and other parts of the pelagic NP (6049). Four main areas of concentration included: a large pelagic area (30-50 degrees N) in the ER, including the Gulf of Alaska and western coast of North America; the northeastern and southwestern CR; and the southern Kurils. Some of the distribution was similar to 19th century catches, notably in the 'Japan Ground' (in the pelagic western Pacific) and the 'Coast of Japan Ground'. Many females were caught in Olyutorsky Bay and around the Commander Islands. There was also a division in catch composition at Amchitka Pass (Aleutians), with family groups to the west and mature males to the east. The extensive illegal catches of females removed a significant portion of the reproductively mature population, which likely continues to impact recovery of NP sperm whales today.