Table 31. --Estimates of the pup population at time of tagging based 

 on recovery of tagged and tag-lost male seals, Pribilof Islands, 

 Alaska, 2 July to 5 August, 1963 



Table 32. --Estimates of pup population at time of tagging based on 

 recovery of tagged and tag-lost 3- and 4-year-old male seals, 



Pribilof Islands, Alaska, 1958-60 year classes 



Date from age 3 only. 



The estimates were made using the modified 

 Petersen formula: 



N 



(n+1) (t+1) 



Where: n 

 t 

 s 



N 



(8+1) 



= number of animals killed from 



age class, 

 = number of tags applied to year 



class, 

 = number of tagged and tag-lost 



animals recovered, and 

 = estimated number of pups at 



time of tagging. 



Several conditions suggest that the most 

 reliable of the three estimates is that which 

 uses the data collected at ages 3 and 4. These 

 are: (1) Lower and upper length limits restrict 

 the kill to large 2-year-old and small 5- and 

 6-year old seals, (2) 2-, 5-, and 6-year-old 

 seals may not be accurately represented in 

 collections of teeth because seals of these 

 ages make up only about 10 percent of the kill; 

 3- and 4-year-old males are well represented, 

 (3) the clubbers may unconsciously select 

 tagged 2-, 5-, and 6-year-old seals for killing, 

 but allow untagged animals of the same sizes 

 to escape. 



The estimates of the total number of pups 

 born (table 33) show a substantial decrease 



Table 33. --Estimates of the number of pups 

 born, Pribilof Islands, Alaska, year 

 classes 1951-61 



1 Douglas G. Chapman. 1961. Preliminary 

 report on the population analysis of Pribilof 

 fur seal herd. In Carl E. Abegglen, Alton Y. 

 Roppel, Ancel M. Johnson, and Ford Wilke. Fur 

 seal investigations, Pribilof Islands, Alaska, 

 Report of Field Activities, June-November 1961. 

 Marine Mammal Biological laboratory, Seattle, 

 Wash. /Manuscript Report^/ 



2 Table 32 of this report, above. 



3 Table 31 of this report, above. 



25 



