THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 155 



Available information indicates that in the 1909-11 period the 

 Amchitka sea otter population may have numbered about 100 

 animals (fig. 74), and that this population reached maximum size 

 of about 4,500 otters in the early 1940's and then "crashed" to 

 about 1,500 animals by 1949. A gradual increase to about 2,000 

 otters apparently occurred between 1949 and 1959, but mortality 

 in the winter-spring period of environmental stress caused the 

 population to stabilize or possibly to decrease in the early 1960's. 



A curve based on field counts and population estimates is shown 

 in figures 73 and 74. An estimated rate of increase of 10 percent 



5000 



4000 



3000 



2000 - 



1000 - 



/ 



/ 



/ 



5 



1909 '12 '15 '18 '21 '24 '27 '30 '33 '36 '39 '42 '45 '48 '51 '54 '57 '60 '63 '66 

 YEAR OF ESTIMATE 



Figure 74. — Estimated curve of the Amchitka sea otter population, 1909-65. 

 No data are available before 1936. The curve from 1909 to 1936 is a pro- 

 jection back from the estimated 1936 population, assuming that the popula- 

 tion increased in this period at an exponential rate of 10 percent per year 

 (see section on Seguam Island). Point 1: Population estimate by Swicegood 



(1936) based on extensive surface counts and observations. Points 2 and 

 3: Population estimates based on the surface counts of Loy and Friden 



(1937) and Loy (1940). Point 4: Estimate based on aerial count by Beals 

 (1943). Point 5: Estimate based on aerial count by Jones (1949). Points 

 6 and 7: Estimate based on aerial counts by Kenyon and Spencer (1960) 

 and Kenyon (1965). 



