during April and May. The high count was 62, the low 40, and the mean 
51. On the aerial survey, 38 otters were recorded in the vicinity of 
Kirilof Point, about 30 of which would probably have been in view from 
the observation areas on land. In accordance with these data, a 
correction factor of about 1.7 should be applied to the aerial count, 
giving an estimated total of (1,560 x 1.7) = 2,652 adult and subadult 
otters at Amchitka. If the correction factor is applied to the total 
otter count for the survey (9,507) the total becomes 16,162 otters. 
Evaluation of counts 
We have demonstrated that counts made from a dory and from an 
aircraft in a sample area at Amchitka may be similar and that shore 
counts in a sample area may reveal roughly twice the number of otters 
seen during an aerial count. 
Variables and unknowns enter counting experiments, and these are 
difficult or impossible to evaluate: 
1. The dory and shore counts were made over a period of 3 months. 
‘During this period, marked fluctuations in the number of otters in any 
given area were observed. Such fluctuations may occur daily in re- 
sponse to changing weather conditions. Therefore, we have no assurance 
that any of the counts used are comparable. 
2. Weather conditions not only cause otters to move from exposed 
to sheltered areas but interfere with visibility. High winds reduce 
efficiency by (1) causing tears to flow in the observer's eyes, and 
(2) causing rough water that obscures the presence of otters. Pre- 
cipitation blurs vision through optical instruments. 
3. At 120 knots in an aircraft an area that may take days to 
cover from shore or in a dory is covered in 5 to 10 minutes. Thus 
the areas chosen for sample surface counts may have been too small. 
It was difficult to place figures correctly on charts during the aerial 
survey because the sample areas were covered so quickly. 
4. Early sea otter hunters reported that otters were sometimes 
found up to 50 miles at sea. We have no information on how many otters 
may be at sea, that is, beyond the approximately 3/4- to l-mile-wide 
strip of water surveyed around each island. Certainly the majority 
are within a quarter of a mile of shore or else concentrated near sub- 
merged offshore reefs. 
For purposes of making rough calculations we may estimate that 
during a calm day at any given time approximately 50 percent of the 
otters in an area are resting on the sea's surface or on rocks and the 
other 50 percent are feeding. Food-diving otters may remain submerged 
for from 1 to 3 minutes and they remain for an approximately equal 
