
and Lukanin-Kitovi, and the Zapadnis (see page 67 ). The estimates of 
the numbers of pups alive on the rookeries adjacent to hauling-ground 
groups used in the calculations are individually subject to large sampling 
errors, particularly because of some of the corrections that enter the 
calculations. However, the errors in the subtotals become less important 
in the overall total, and the estimate of 393,953 pups alive on the five 
reokery groups at the time of the 1947 tagging is considered valid (see 
page 69). 
The 1948 population could, in similar fashion, be estimated 
from the return of B-series tags applied in that year, were it not for 
two obstacles. First, the B-tags were applied on only three rookeries, 
Polovina, Reef, and Zapadni, with relatively few on Zapadni; and past 
experience has shown that Reef-born seals tend to return, because of 
unsatisfactory hauling grounds near their home rookery, to Tolstoi, 
Lukanin-Kitovi, and Northeast Point hauling grounds. These are precisely 
the ones that must be omitted in the estimate procedure. Second, the 
B-tag returns are as yet incomplete, until the 1952 and 1953 data are 
analyzed. 
Estimated number of pups born on the Pribilofs in 1947.--The 
foregoing estimates apply to St. Paul Island only and to the pups alive 
during the tagging period, 24 September - 10 October. Also excluded 
are Ardiguen and Sivutch rookeries where tagging was not done. First, 
it is desirable to round out the above estimate and, since any overlooked 
_lost-tag scars will tend to inflate the estimate, it is preferable to 
round it downward. Second, it is estimated by rough interpolation that 
about 50,000 pups had died on St. Paul in 1947 before the midpoint of the 
tagging season (table 11). Thus the estimated number of pups born on St. 
Paul is 390,000 plus 50,000 or 440,000. 
To estimate the number born on the Pribilofs, the harem-bull 
count is used as a basis for extrapolation. On the basis of bull counts 
in 1947, St. Paul, excluding Sivutch and Ardiguen rookeries, appeared to 
have 82.3 percent of the Pribilof population. Consequently, the estimated 
number of pups born on the Pribilofs in 1947 rounded to the nearest ten 
thousand is 530,000. 
Sample counts and rapid field estimtes of living pups, and counts of 
dead pups. 
From 1912 to 1924, when the herd was small, a counting method 
successfully employed was to drive the pups past observers (fig. 9). 
The method was used briefly in 1940, in 1949, and again in 1951 in an 
attempt to get accurate sample counts on small rookeries. Because the 
pups are badly frightened, gather in compact groups, and are difficult 
to handle, the method is considered a last resort. However, it appears 
to be sufficiently accurate to merit some consideration. Sample counts 
obtained in this way have been linked with the harem—-bull counts and to 
ground-area measurements obtained from aerial photographs to obtain two 
additional estimates. 
--eo- 
