MARINE MAMMAL COMMISSION — Annual Report for 1991 



harbor seal report. The updated report will review 

 and make recommendations for needed research and 

 management actions, including: (1) evaluating popu- 

 lation status by monitoring relative population sizes 

 and trends and the health, condition, and vital parame- 

 ters of harbor seals; (2) coordinating cooperative 

 actions involving the Alaska Department of Fish and 

 Game, the National Marine Fisheries Service, the Fish 

 and Wildlife Service, and the National Park Service; 

 (3) initiating a comprehensive study of harbor seals in 

 Bristol Bay, Alaska, where large concentrations of 

 harbor seals occur; (4) studying direct and indirect 

 effects of commercial fisheries on harbor seals; 

 (5) studying the effects of existing and potential 

 harvests on harbor seals; and (6) studying the short- 

 and long-term effects of anthropogenic disturbance, 

 especially in areas subject to heavy boat and aircraft 

 traffic. 



species' largest breeding colony is on the Pribilof 

 Islands, where three-fourths of the global population 

 is found. It is estimated that, when the Pribilofs were 

 discovered in 1786, the islands' fur seal population 

 numbered 2-2.5 million animals. Their numbers 

 subsequently fluctuated widely. Despite being re- 

 duced to about 300,000 animals by 1912, the fiir seal 

 population on the Pribilofs recovered to what is 

 believed to have been historically high levels in the 

 late 1940s and early 1950s. From the late 1950s to 

 the mid-1980s, however, the number of fur seals on 

 the Pribilof Islands experienced two periods of decline 

 with a net reduction of 60-70 percent. Population 

 estimates from the mid- 1980s place the number of 

 seals on the islands at about 870,000 animals, and it 

 is believed that the population has remained stable 

 since that time. A similar decline was observed at 

 Robben Island. 



The updated report is expected to be completed 

 early in 1992. The Commission, in consultation with 

 its Committee of Scientific Advisors, will review the 

 report to determine whether harbor seals in Alaska 

 merit designation as depleted under the Marine 

 Mammal Protection Act or as either threatened or 

 endangered under the Endangered Species Act. 



As a related matter, the Commission held a work- 

 shop on 12-13 December 1990 in Seattle, Washington, 

 to identify research needed to resolve critical uncer- 

 tainties concerning the decline of Steller sea lions, 

 harbor seals, fiir seals, and other species in the Bering 

 Sea and Gulf of Alaska (see Chapter VII). The final 

 workshop report, published in July 1991, concluded 

 that a reduction in available food resources and 

 incidental take in fisheries were likely to be major 

 factors in the observed harbor seal declines. 



North Pacific Fur Seal 

 (CaUorhinus ursinus) 



North Pacific or northern fur seals occur seasonally 

 in waters along the North Pacific rim from California 

 to Japan. Major breeding locations occur on Robben 

 Island and the Kuril Islands in the Okhotsk Sea, in the 

 western Bering Sea on the Commander Islands, and 

 on the Pribilof Islands in the eastern Bering Sea. The 



Although causes of the observed declines are not 

 known, several factors may have affected or be 

 affecting North Pacific fiir seals. Between 1956 and 

 1968, more than 300,000 female fur seals were 

 harvested in Alaska. At the time, it was believed that 

 the harvest would result in greater overall productivity 

 within the population. The predicted increase never 

 occurred. Because some nursing females were taken, 

 many of their pups died. The death of these adult 

 females prevented this further contribution to the 

 population. 



From the mid-1970s to the early 1980s, the Pri- 

 bilof Islands' fur seal population declined at a rate of 

 approximately 4-8 percent per year. In the early 

 1980s, it was suggested that a major cause of this 

 decline was entanglement of seals in marine debris 

 such as net fragments and packing bands. Analyses 

 by the National Marine Fisheries Service estimated 

 that approximately 50,000 juvenile seals (those up to 

 three years old) were lost due to entanglement every 

 year. Direct evidence of such losses, however, was 

 weak. Observed entanglement rates from counts of 

 entangled juvenile male fiir seals taken in harvests on 

 the Pribilof Islands in the late 1970s were only about 

 0.4 percent. Since the late 1980s, observed entangle- 

 ment rates on the islands have declined to an estimat- 

 ed 0.34 percent in 1990. 



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