ALASKA FISHERY AND FUR-SEAL INDUSTRIES, 1922. 



113 



Distribution of pups on Pribilof Islands in 1922 and comparison with distri- 

 bution in 1921. 



The results of the complete pup count show conclusively that the 

 estimates of pups made annually since 1916 have been, in general, 

 correct. In fact, the largest differences between the percentage of 

 increase in 1921 and that in 1922 are found on the rookeries that 

 have been counted both years. Polovina and Polovina Cliffs rook- 

 eries, counted in 1920 and 1921, showed a percentage of increase of 

 1.08 and 8.24, respectively, in 1921. In 1922 the increase was 44.46 

 per cent for Polovina and 41.8 per cent for Polovina Cliffs. Keef 

 rookery, next to Vostochni the largest rookery on the islands, was 

 estimated in 1920 to have increased 5.26 per cent and in 1921 to 

 have increased 4.23 per cent. The count of 1922 showed an increase 

 of 3.3 per cent. The estimate of pups on Vostochni rookery in 1921 

 showed an increase of 22.33 per cent, but the count in 1922 showed a 

 decline of 7.18 per cent. It may be that the 1921 figure was too 

 high, but the difference between the 1921 and 1922 figures for this 

 rookery is less than the difference between those for Polovina 

 (counted in both years), proving that it is possible for Vostochni to 

 vary as the figures show. 



Since the variation in the annual rate of increase on one rookery 

 and the variation in the increase of the different rookeries in the 

 same year are so great, a constant rate of increase can not be given 

 for any one rookery nor can the same rate of increase be applied 



