ALASKA FISHERY AND FUR-SEAL INDUSTRIES, 1931 



93 



for all females to be impregnated and resulting therefore in a greater 

 increase in birth rate the following year. 



On account of the fact that more densely populated and more 

 favorably situated rookeries increase, as a rule, faster than the sparsely 

 populated areas, it will also be necessary some time to make proper 

 adjustments to show more accurately the number of animals on each 

 separate rookery. 



The proportion of dead pups found on the various rookeries in 

 1922 has again been applied to each rookery. For comparative 

 purposes, to show the actual number of cow^s on hand, and to provide 

 figures on which to base the increase for the following year, it is nec- 

 essary to include the estimated number of dead pups in the total 

 number of pups. 



Distribution of pups on the Pribilof Islands, August 10, 1931, and comparison iviih 



distribution in 1930 



Rookery 



St. Paul Island: 



Kitovi.. 



Lukanin 



Gorbatch 



Ardiguen 



Reef 



Sivutch.- 



Lagoon (actual count) 



Tolstoi.... 



Zapadni , 



Little Zapadni 



Zapadni Reef 



Polovina 



Polovina Cliffs , 



Little Polovina 



Morjovi 



Vostochni 



Total 



St. George Island: 



North 



Staraya Artil. 



Zapadni 



South 



East Reef 



East Cliffs 



Total 



Total (both islands) 



Living 

 pups 



11, 689 



5,611 



29,861 



2,781 



,59,618 



18, 061 



114 



35, 121 



33, 639 



17,011 



601 



12, 112 



6,610 



2,391 



4,320 



48, 059 



287, 599 



23, 535 

 17, 521 

 2,510 



585 

 5,387 

 15, 383 



64, 921 



352, 520 



1931 



Dead 

 pups 



174 

 124 

 259 

 68 

 883 

 452 



436 

 5 



125 

 62 



1,021 



4,970 



334 

 464 

 28 

 10 

 83 

 233 



1,152 



6,122 



Total 

 pups 



11,863 



5,735 



30, 120 



2,849 



60, 501 



18, 513 



114 



35,616 



34, 228 



17,447 



606 



12,300 



6,735 



2, 453 



4,409 



49, 080 



292, 569 



23, 869 

 17, 985 



2,538 

 595 



5,470 

 15,610 



66, 073 



358, 642 



Per cent 

 dead 

 pups 



1.47 

 2.17 

 .86 

 2.39 

 1.46 

 2.44 



1.39 

 1.72 

 2.50 

 .80 

 1.53 

 1.85 

 2.51 

 2.02 

 2.08 



1.70 



1.40 

 2.58 

 1.12 

 1.72 

 1.51 

 1.49 



1.74 



1.71 



1930 



Total 

 pups 



10. 984 



5,310 



27, 889 



2,638 



56, 020 



17, 142 



113 



32, 978 



31, 693 



16, 1.55 



561 



11,389 



6. 236 



2,271 



4,082 



45, 444 



270, 905 



22, 101 

 16, 6,53 

 2, 3J0 



551 

 5,065 

 14, 459 



61, 179 



332, 084 



Increase 



879 



425 



2,231 



211 



4,481 



1,371 



1 



2,638 



2,535 



1,292 



45 



911 



499 



182 



327 



3,636 



21,664 



1,768 

 1,332 



188 

 44 



405 

 1.157 



26, 568 



MORTALITY OF SEALS AT SEA 



No change was made in the mortality rates used this season to de- 

 termine the number of seals of various ages in the herd. Though the 

 mortality rate of seals at sea undoubtedly varies considerably from 

 year to year, the present ultraconservative rates used answer all 

 practical purposes to determine the approximate number of animals 

 in the herd. It will be necessary, however, to make temporary ad- 

 justments from time to time when actual observations show a greater 

 number of animals on hand than census figures indicate; for instance, 

 during the present season it was very evident, from observations and 



121070—32 7 



