MARINE MAMMAL COMMISSION - Annual Report for 1995 



Northern Fur Seal 

 (Callorhinus ursinus) 



Northern fur seals occur in coastal waters of the 

 North Pacific Ocean from southern California to Japan 

 and in pelagic waters from about 35 degrees north 

 latitude to the central Bering Sea (Figure 2). Ap- 

 proximately three-fourths of all northern fur seals 

 breed and pup on Alaska's Pribilof Islands. Most 

 other northern fur seals breed in Russia on the Rob- 

 ben Islands, the Kuril Islands, and the Commander 

 Islands. Two small rookeries also occur on San 

 Miguel Island in southern California and Bogoslof 

 Island in the central Aleutian Islands. 



Northern fur seals exhibit a high degree of site 

 fidelity. Most animals three years of age or older 

 return to their natal islands in summer to breed, pup, 

 and molt. Tagging studies document only occasional 

 movement of individuals between the various rookery 

 sites. At other times of the year, fur seals generally 

 remain at sea feeding, sometimes migrating long dis- 



tances. Most one-year-old fur seals and some two- 

 year-old animals remain at sea year-round. 



Northern fur seals were harvested commercially for 

 their pelts beginning in the late 1700s. By the 1800s 

 excessive pelagic harvests of males and females of all 

 ages threatened the species' economic as well as 

 biological viability. As a result, the principal harvest- 

 ing nations — Canada, Japan, Russia, and the United 

 States — signed the Fur Seal Treaty of 1911. The 

 treaty banned pelagic harvests in lieu of arrangements 

 to share pelts from a managed onshore harvest of sub- 

 adult male seals taken on U.S. and Russian rookeries. 

 By limiting the harvest to sub-adult males, fur seal 

 numbers were able to increase substantially over the 

 next 30 years. 



With World War II, the treaty and fur seal harvests 

 lapsed, and by the early 1950s the Pribilof Islands' fur 

 seal herd had swelled to about two million animals — 

 a number thought to be at or near its pre-exploitation 

 size. Harvests were soon resumed on the Pribilof 

 Islands. At the time the prevailing wildlife manage- 



Figure 2. Range and breeding islands of the northern fur seal 



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