extensively used. With fur seals, unfortunately, the method requires 3 
years for results. If data to be used in forecasting the commercial 
kill from the pup class of any given year were required, it would be 
necessary to resort to a more direct method, say, rapid field estimating 
or sample counting on selected index rookeries. 
Table 8.-—~Number of pups counted on the Pribilofs, 1912-24. 
(Scattered and incomplete counts were made before 1912 and 
are not comparable with later series. For example, see Jordan 
1898, part 1, pp. 92 and 96.] 

Number of St. George Number of Number of 
St. Paul Island pups on all [Island counted pups on all pups on all 
counted out o St. Paul out of 6 St. George Pribilof 
Year 16 rookerie rookeries’/ rookerie rookeries rookerie 
1912 all 70 ,035 all 11,949 81,984 
1913 all 79,458 all 12,311 92, 269 
1914 all 79 , 383 all 13,867 93,250 
1915 all 88 ,137 all 15,390 103,527 
1916 all 98,855 all 18,122 116,977 
1917 8 108 , 689 3 19,335 128,024 
1918 A 122,617 3 20,298 142,915 
1919 5 133,914 4 23,258 157,172 
1920 5 143,275 3 24,252 167,527 
1921 5 149 , 865 3 26 ,'790 176 ,655 
1922 all: 158 ,886 all 27,028 185,914 
1924 5 172,528 3 35,868 208 , 396 
— 

1/ Pups were counted on tiny Lagoon rookery from 1912 to its disappearance 
in 1942, leaving 15 rookeries on St. Paul Island. 
2/ Total living and dead; where counts were made on part « of the rookeries, 
estimates were projected to the uncounted ones. 
3/ In 1915 South rookery was first listed by name although a few seal 
pups had been seen there as early as 1912. In 1915 Little East rookery 
was abandoned and the name was dropped. The total effect was to leave 
6 rookeries on St. George. 
Normally when a single tagging operation is conducted, the 
population estimate is based on the Petersen formula (Ricker, 1948, p. 39). 
This assumes that a random sample is taken of the population so that the 
unknown percentage of the population marked may be equated to the known 
percentage of marks or tags obtained in the sample. Here the population 
estimate is based on the number of male pups alive at the time of tagging 
on St. Paul in 1947. Several complicating factors immediately arise. 
-20- 
