1999 

 OUR LIVING OCEANS 



Section 1 19 of the Act. The process should also 

 include a sound research and management pro- 

 gram to identify and address uncertainties con- 

 cerning the stocks. 



Table 22-1 presents a summary of the status 

 of stocks tor the marine mammals in the Alaska 

 region. Important population parameters tor the 

 stocks and their status under the various protected 

 species laws are included. These include: stock 

 identification, N (a conservative estimate ot 

 abundance used to estimate the PBR, which is the 

 ma.ximum allowed level ot human-related removal 

 in a given year), estimates ot current human-re- 

 lated mortality, population status, and current 

 population trend. A narrative tor some selected 

 stocks tollows: 



STELLER SEA LION: 



EASTERN AND U.S. WESTERN 



NORTH PACIFIC STOCKS 



Stock Definition 



and Geographic Range 



Steller sea lions range along the North Pacific 

 rim from northern Japan to California, with his- 

 toric centers of abundance and distribution in the 

 Gulf of Alaska and Aleutian Islands, respectively 

 The species is not known to migrate, hut indi- 

 viduals disperse widely outside ot the breeding 

 season (late May-early July), thus potentially in- 

 termixing with animals from other areas. Two sepa- 

 rate stocks of Steller sea lions are recognizee! within 

 U.S. waters: an eastern Pacific stock, which in- 

 cludes animals east of Cape Suckling, Alaska 

 (144^'W), and a western U.S. Pacific stock, which 

 includes animals from Cape Suckling wesrward. 

 Steller sea lions in Canada are part ot the eastern 

 Pacific stock. 



Population Size 



ing correction t.ictors derived from previous sur- 

 veys, the 1996 surveys resulted in an estimated 

 39,500 Steller sea lions (33,700 nonpups and 

 8,800 pups) for the entire Cult ot Alaska, Aleu- 

 tian Islands, and Bering Sea region that comprises 

 the western U.S. Pacific stock. A comparable esti- 

 mate tor the eastern Pacific stock is not possible. 

 However, counts from the southeast Alaska, Brit- 

 ish CA)lumbia, Clilitornia, and Oregon region in- 

 dicate a population ot at least 30,400 Steller sea 

 lions. 



Minimum Population Estimate 



Using the population estimate (N) ot 39,500 

 and an a.ssociated CV of 0.0184, N,^,^,^ for the 

 western U.S. Pacific stock is calculated as 38,893 

 (Table 22-1). The population estimate for theeast- 



Steller sea lion bull, cow, 

 and pup. Southeast Alaska. 



An estimate ot Steller sea lion abundaiice in 

 Alaska is made possible using survey data collected 

 in June and lulv of 1996, from California to the 

 western Aleutian Islands. The surveys iiicluded 

 counts ot animals, excluding pups, at 9S "trend 

 sites," where sea lions in the western U.S. Pacific 

 stock have been monitored since the 1970's. Us- 



'Cocfficient of v.iri.iiion (t'V) is a statisticai measure used to 

 calculate confidence intervals (CI), which gauge the accuracy 

 ot population estimates. An accurate population estimate is 

 characterized by a low CV and a narrow CI. CI is often given 

 a percentage likelihood ot being correct (e.g. 9^% means that 

 if the data were rcsampled and the CI were recalcul.iicd Hill 

 times, then 95 times it would contain the true value. 



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