106 



V. S. BUEBAU OF FISHERIES 



To fully understand methods of computation and reasons for 

 applying various mortality rates, it is necessary to consider census 

 estimates for the past several years. These figures show reasons for 

 making changes in mortality rates from year to year. It will not be 

 necessary to reiterate these changes at this time, but the reader will 

 find more complete data in the corresponding annual reports for 1928 

 and 1929. . 



COMPLETE COMPUTATION 



Following is a summary of computations of the number of animals 

 in the Pribilof Islands fur-seal herd in 1930, together with a recapitu- 

 lation of the herd by classes. It will be noted that the increase in 

 the total number of seals over 1929 was 73,574, or 7.57 per cent. 

 The increase in 1929 over 1928 was 100,014, or 11.48 per cent. This 

 large increase in 1929 was due to a readjustment of figures for pre- 

 vious years on account of additional information secured regarding 

 mortality rates of seals at sea. 



Complete computation of fur seals, Pribilof Islands, as of August 10, 1930 



Class 



Pups, estimated _ 



Breeding cows, 3 years old and over, by inference. 



Harem bulls, counted 



Idle bulls, counted 



St. Paul 

 Island 



270, 905 



270, 905 



6,823 



1,555 



St. George 

 Island 



Yearlings, male and female, estimated: 



Females born in 1929 I 125,422 



Natural mortality, 40 per cent -I 50, 169 



Yearling females, Aug. 10, 1930. 



75, 253 



Males born in 1929 I 125, 422 



Natural mortality, 40 per cent I 50, 169 



Yearling males beginning 1930 - 



Yearling males killed 1930 



75, 253 

 15 



Yearling males, Aug. 10, 1930. 



3-year-olds, male and female, estimated: 



Yearling females, Aug. 10, 1929 



Natural mortality, 15 per cent 



2-year-old females, Aug. 10, 1930. 



Yearling males, Aug. 10, 1929.. 

 Yearling males killed fall 1929. 



Yearling males end of 1929 



Natural mortality 17.6 per cent. 



2-year-olds beginning 1930- 

 2-year-olds killed 1930 



2-year-old males, Aug. 10, 1930. 



.3-year-old males, estimated: 



2-year-old males, Aug. 10, 1929.. 

 2-year-old males killed fall 1929. 



2-year-old males end of 1929 



Natural mortality, 12.5 per cent. 



3-year-old males beginning 1930. 

 3-year-old males killed 1930 



3-year-old males, Aug. 10, 1930. 



75,238 



69, 682 

 10, 452 



59, 230 



69,645 



69,645 

 12, 188 



57, 457 

 712 



56, 745 



52,404 

 23 



52, 381 

 6,548 



45. 833 

 33, 393 



12,440 



61, 179 



61, 179 



1,489 



344 



28,323 

 11,329 



16, 994 



28,324 

 11, 330 



16, 994 



16,994 



15, 735 

 2,360 



13,375 



15, 736 



15. 736 

 2,754 



12, 982 

 53 



11, 950 

 10 



11, 940 

 1,493 



10, 447 

 8,016 



2,431 



Total 



332, 084 



332, 084 



8.312 



1,899 



153, 745 

 61, 498 



92,247 



153,746 

 61, 499 



92, 247 

 15 



92,232 



85, 417 

 12,812 



72, 605 



85, 381 



85. 381 

 14,942 



70, 439 

 765 



12,929 I 69,674 



64,354 

 33 



64.321 

 8,041 



56.280 

 41,409 



14,871 



