Northern Sea Lion (Eumetopias iubatus) 



Northern or Steller sea lions occur in coastal areas 

 throughout the rim of the North Pacific Ocean from northern 

 Hokkaido, Japan, through the Kuril Islands and Okhotsk Sea, 

 the Aleutian Islands and central Bering Sea, the southern 

 coast of Alaska, and the coasts of British Columbia, Washington, 

 and Oregon, south to the California Channel Islands. Numbers 

 are greatest and the largest pupping colonies occur in the 

 Gulf of Alaska and the Aleutian Islands. 



Available information indicates that northern sea lion 

 populations have been declining since the late 1970s in the 

 Kuril, Commander, Aleutian, and Pribilof Islands, in Bristol 

 Bay and the central and western Gulf of Alaska, and in Cali- 

 fornia. The cause or causes of the decline have not been 

 documented. On 9-10 December 1986, the National Marine Mammal 

 Laboratory convened a workshop to review available information 

 and identify research necessary to determine the cause and to 

 better document the nature and extent of the decline. 



The workshop report, published in March 1987, indicates 

 that the number of adult and juvenile northern sea lions on 

 haul-out sites in the central Gulf of Alaska through the central 

 Aleutian Islands declined 52 percent, from 140,000 animals in 

 1956-1960 to about 68,000 animals in 1985. The greatest 

 declines have been in the eastern Aleutian Islands, where 

 estimated numbers in 1985 were 79 percent less than in 

 1956-1960. The workshop concluded that the decline was con- 

 tinuing and likely was due to reduction in juvenile and adult 

 female survival rates. The workshop also noted that declines 

 in northern fur seals, harbor seals, and fish-eating birds 

 apparently have occurred in the Gulf of Alaska and the Bering 

 Sea in recent years as well. 



Possible causes of the observed sea lion decline include: 

 incidental take in fisheries; deliberate shooting by fishermen; 

 reduction of important sea lion prey species due to fishery 

 development; entanglement in lost and discarded fishing gear 

 and other marine debris; disease; environmental pollution; 

 and natural changes in the marine ecosystem of which northern 

 sea lions are a part. The workshop concluded that available 

 information was insufficient to assess reliably the likely 

 significance of any of the possible causes and recommended 

 that steps be taken to: obtain more reliable information on 

 the numbers of sea lions, by age and sex, being killed inci- 

 dentally and deliberately during domestic and foreign fishing 

 operations offshore Alaska; complete the analysis of data 

 from disease studies conducted in 1985-1986 and initiate 

 additional studies as may be needed; salvage and do necropsies 

 on animals found dead on beaches in selected rookery areas 

 (e.g., Marmot Island, Alaska) to determine the nature, extent, 



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