THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 163 



and was not surveyed in 1962) increased from 6,107 otters in 1959 

 to 6,849 in 1962 (table 25), a gain of 742 otters or 12.1 percent in 

 3 years. In the next 3-year period (1962-65) the same area gained 

 858 otters (7,707 minus 6,849, table 25) or 12.5 percent. 



Within the Andreanofs, emigration occurred when islands be- 

 came densely populated. For example, the Kanaga population lost 

 1,301 otters (2,429 minus 1,128, table 25) between 1959 and 1962, 

 while nearby islands (Adak, Kagalaska, Little Tanaga, Umak, 

 Anagaksik, Great Sitkin, and adjacent islets) increased from 

 2,292 to 4,269 (table 25), a gain of 1,977 otters or 86 percent. 

 Because immigrating otters may have moved into the available 

 vacant habitat surrounding the above named islands from Tanaga 

 as well as Kanaga, it is not possible to separate the increase repre- 

 senting reproduction from that caused by immigration in these 

 areas. The conclusion is indicated that in the Andreanofs the total 

 sea otter population may grow at a rate of about 4 to 5 percent 

 per year and that in the 1975 to 1980 period the population there 

 may number over 12,000 otters or about 14 animals per square 

 mile of habitat. 



Tanaga Island. — The repopulation of Tanaga Island appears to 

 have been well underway by the mid-1930's. Williams (1937) 

 mentions it along with Amchitka and Ogliuga as being one of the 

 *'most productive" islands. D. Hooper {in Jones, 1953) indicated 

 that the otter population there was large in 1953. Until our aerial 

 surveys, no comprehensive quantitative assessment of the otter 

 population at Tanaga was made. Available population data are 

 summarized in table 26. 



The few observations available indicate that population overflow 

 from the Delarof Islands repopulated Tanaga during the 1930's, 

 and that during the late 1940's or early 1950's the local population 

 reached maximum size. During the mid- or late-1950's, the popula- 

 tion density probably became reduced through emigration to 

 Kanaga Island and remained stabilized from 1959 to 1962 at about 

 14 otters per square mile of habitat. The increase to about 17 



Table 26. — Tanaga Island sea otter population density in 83 square miles of 



feeding habitat 



Estimate Otters per Authority and 



Year Count of total square mile survey method 



1937 (?) 150+ 2 O. J. Murie and V. B. SchefFer, 



surface survey. 



1953 1,000 (ca.) 1,000+ 12+ D. Hooper, surface survey (w 



Lensink, 1960). 



1959.. 902 1,203 14 Spencer and Kenyon, aerial survey. 



1962 — 898 1,197 14 Spencer and Kenyon, aerial survey. 



1965 1,059 1,412 17 Spencer and Kenyon, aerial survey. 



