FUR-SEAL CENSUS, PRIBILOF ISLANDS, 1923 



By Edward C. Johnston 



In the past few years the census of the harem and idle bulls has 

 been taken between the dates July 16 and 28. This period was that 

 in which there was a maximum number of harems, and it immedi- 

 ately preceded the breaking up of the harem formations. A few 

 years ago, w^hen there was a large number of idle bulls and the average 

 harem was comparatively small, this breaking up of the harem forma- 

 tion did not occur before July 23, and the difficulty of counting, due 

 to the idle bulls, was such that it took seven days on the two islands to 

 complete the count. In 1923 the counting was started on St. Paul 

 Island on July 16 and completed by July 19. On St. George Island 

 the count was made on July 21 and 22. By Julj^ 19, however, it was 

 seen that a few harem bulls had retired to the rear of the rookeries 

 and their places had been taken by the young idle bulls. 



On account of landing conditions it was impossible to get to 

 Sivutch rookery on Sea Lion Rock during the period Avhen the 

 harems should have been counted. This rookery is situated on a 

 small island in the open sea and is surrounded by shoal water. It 

 does not require much wind to prevent a landing. 



Superintendent H. J. Christoffers accompanied the enumerator on 

 St. George Island and verified the count there. The ease with which 

 the harem areas could be approached, together with the fact that the 

 count was checked by a second person, practically eliminated the 

 possibility of error. 



PUPS 



The count of pups in 1923 was omitted with the understanding 

 that in 1924 an actual count Avould be made upon those rookeries 

 that could be counted accurately. 



A complete pup count on all rookeries was made in 1916 and 

 another in 1922. Between these years the pups on a few of the 

 rookeries were counted, and from the results obtained the pups on 

 the other rookeries were estimated. In 1923. as a basia in computing 

 the number of pups, the average annual increase in the average harem 

 upon those rookeries counted each year was secured. Applying this to 

 the 1922 figures it was found that the average harem for the counted 

 rookeries increased on St. Paul Island from 42.98 in 1922 to 47.96 

 m 1923. On St. (xeorge Island it increased from 46.72 to 53.28. The 

 average harem on the other rookeries was computed in the same 

 manner as it had been in the 3'ears 1917 to 1921. With this average 

 harem and the known number of harem bulls the number of cows 

 and pups Avas obtained. 



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