Table 1 1 . --Numbers of sea lions observed in 

 Southeastern Alaska, 1957 



Location 



Visual estimate 

 from airplane 



Cape Addington 



Biorka Island 



Forrester and Lowrie Islands 



Hazy Island 



Cape Ommaney 



St, Lazaria 



Timbered Island 



Total 



8,715 



Source of data: U.S. Fish and Wildlife Service 



The decline in number of animals from the 

 Gulf of Alaska and southward corresponds to 

 the decline on the Kurile Islands on the same 

 latitude (Klumov, 1957) and is probably con- 

 nected with climatic conditions. 



Mathisen (1959) estimated 165,000 Steller 

 sea lions along the North American Pacific 

 Coast, This estimate has been raised to about 

 175,000 animals by the figures given in this 

 report. Kenyon and Rice (1961) estimated the 

 world population of Steller sea lions to be 

 about 225,000. From all of these figures it is 

 apparent that the center of population density 

 is from the entrance of Cook Inlet to Unalaska. 

 Actual photo counts are given for all the 

 important rookeries in this area. 



SUMMARY 



1. Predation has been cited as a contribut- 

 ing factor to the decline in runs of salmon 

 in Alaska. Since Steller sea lions and harbor 

 seals are known to eat salmon, they are listed 

 among the predators. 



2, A realistic appraisal of damage by sea 

 lions to food fish requires knowledge of the 

 areas and periods of time where these animals 

 feed and an exact estimate of the total popu- 

 lation size. 



3. Previous methods of estimating marine 

 mammals could not be used because of the 

 many separate populations widely scattered 

 in Alaska. 



4. A photographic census technique was 

 developed and is described. 



5. The accuracy of the method is discussed 

 for various categories of Steller sea lions. 



6. All photographic estimates of the sea 

 lion herds for the years 1956, 1957, and 1958 

 have been summarized in tabular form. The 

 area covered extends from Cape St. Elias 

 (144° W.) to the Islands of the Four Mountains 

 (170° W.) 



7. Diurnal variations were demonstrated, 

 with the highest number of animals seen on 

 the rookeries during daytime. 



8. Pronounced seasonal variations were 

 found, with a summer population two to three 

 times as large as the winter one. 



9. A limited survey was made of the harbor 

 seals, and about 18,000 animals were photo- 

 graphed during the summer months. 



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