Personnel included the following: 
Theron Smith, FWS Aircraft Supervisor, Pilot. 
Jim Tilford, Bureau of Land Management, Co-pilot. 
David L. Spencer, FWS Regional Refuge Supervisor, Observer. 
Karl W. Kenyon, FWS Biologist, Observer. 
Norman J. Wilimovsky, FWS Biologist, Bureau of Commercial 
Fisheries who accompanied all flights primarily to look 
for herring concentrations. 
METHODS OF SURVEY 
Five requirements must be met if a census survey of sea otters 
by aircraft is to be of value: (1) The pilot of the aircraft must co- 
operate completely with the observers and must have considerable 
experience in survey work. Frequent circling back over areas is 
necessary and the pilot must, by experience, know exactly how to 
place the observers in position .to best see a certain spot. (2) Two 
observers are essential. They must divide the area to be viewed in 
half, each counting all otters on his side of the centerline of the 
aircraft flight path. (3) The observers must have a clear view of all 
areas directly ahead and on both sides of the aircraft. (4) The 
observers must be familiar both with aerial survey work and with sea 
otters. .(5) Weather must be nearly calm; an overcast sky is best for 
observation. . 
Fortunately, all of these requirements could be met in the May 
1959 aerial survey of the outer Aleutian Islands. 
When large groups of otters were found, counts were of necessity 
supplemented by estimates. In such instances each observer made an 
independent estimate, then a final figure was agreed upon. In all 
cases both estimates were similar. Groups of.more than 100 animals 
were infrequently seen. 
The altitude of flight was sometimes dependent on terrain and wind 
conditions. For most of the survey an altitude of 300 feet above the 
water was maintained, but under some conditions it was necessary to go 
briefly to 500 feet. An airspeed of about 120 knots was maintained. 
The advantages and disadvantages of aerial, dory, and shore 
surveys, as methods of censusing sea otters, are tabulated below. 
Aerial surveys 
Advantages: 
1. Survey is made rapidly, and errors introduced by movements of 
otters from one area to another are eliminated. 
2. Hundreds of miles of otter habitat may be covered in a few 
hours of flight time. | 
