THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 159 



on the east by 14-mile-wide Tanaga Pass and from the Rat Islands 

 on the west by 50-mile-wide Amchitka Pass. The Delarofs have 

 no human inhabitants. 



Murie (1940) found a thriving sea otter population at Ogliuga 

 in 1936. Joynt (1957) says of his 1943 aerial observations that — 



The most densely grouped of any pod of sea otter observed was on one end 

 of the sand bars exposed at half tide that lies between Kavalga Island and 

 Ogliuga Island in the Delarof Islands group. 



Data from the 1930's, as cited above, indicate that the Delarof 

 and Rat Islands populations approached maximum size at about 

 the same time. Because of the width of Amchitka Pass (50 miles), 

 it appears probable, as pointed out by Lensink (1960), that rem- 

 nant populations remained in 1911 in both the Rat and Delarof 

 Island groups. The habitat at Amchitka and in the Ogliuga- 

 Kavalga Islands areas, is similar in having extensive shallows 

 dotted by submerged or partially submerged reefs. Although these 

 olTered feeding habitat and a place of refuge to the sea otter, they 

 presented considerable hazard to early sea otter hunters and were 

 probably instrumental in preserving the species. 



On 26 May 1959, our aerial observations (table 24) revealed 

 that the number of otters per square mile of habitat in the Delarofs 

 was the highest of any island group that we surveyed. This condi- 

 tion is of particular interest because the Delarofs were among the 

 first Aleutian islands to be repopulated. By May 1965, our observa- 

 tions indicated that the Delarof population had dropped by ap- 

 proximately 50 percent (table 24). 



It may be postulated that after the population peak, which 

 probably occurred in the 1930-40 period, emigration to Tanaga 



Table 24. — Delarof Islands sea otter population density estimated from aerial 

 survey counts of 26 May 1959 and 2-3 May 1965 



Otters esti- 



Otters Estimated mated per 



counted total Square square mile 



miles of 



Island 1959 1965 1959 1965 habitat i 1959 1965 



Gareloi 41 83 68 111 9 8 12 



Unalga 51 16 85 27 8 10 3 



Kavalga 275 155 



Ogliuga 112 144 



Skugul-Tag-Ugidak 281 46 375 J> 2 1,152 77 >• 529 52 22 10 



Gramp Rock 134 1 00 



Ilak.._ 49 / '^^ 



Ulak 352 107 



Amatignak 102 70 



2 605 \ 260 20 30 13 



Total 1,397 653 1,910 927 89 Av. 21 10 



1 Includes water of 30 fathoms or less in depth as measured from U.S. Coast and Geodetic 

 Survey charts. 



2 Closely associated islets and islands. 



