1968; and the number of 3-year-old males re- 

 maining- after the kill in 19(56. All estimates 

 except that of the number of pups born in 

 1969 are based on marked male seals recovered 

 in the kill. The number of pups born in 1969 

 was estimated by shearing and sampling live 

 pups in August. 



Number of Seal Pups Born 



Male seals marked as pups and recovered 

 during the kill in 1969 provided a basis for 

 making estimates of the number of pups at 

 the time of marking- for year classes 1963-67 

 (table 9). Some pups of the 1965 and 1966 

 year classes had been marked by tagging and 

 others had been marked by removing part of a 

 flipper (table A-17). Separate population 

 estimates for year classes 1965-66 were made 

 on the basis of recoveries from each group of 

 marks. For the 1965 year class, the estimate 

 based on tag recoveries was only slightly higher 

 than the two estimates based on recoveries 

 of seals marked by removing part of a flipper. 



Table 9. --Estimates of the seal pup population, year classes 1963-67, 

 at time of marking from recoveries of marked male 

 seals in ages 2. to 6, Pribilof Islands, Alaska 



314, 121 



398, 021 



331, 094 

 326, 737 

 354,722 

 337,631 



399, 844 

 47 5, 541 

 434, 134 



349, 244 



!_/ Estimates do not include counts of dead pups. 



z , A (C+1)(M*1) 



(R+l) 

 3/ Marked by tagging. 



4/ Marked by cutting a V-notch into the leading edge of the 

 right front flipper. 



5/ Marked by removing the tip of the first digit on the right 

 hind flipper. 



6/ Marked seals of the year class combined. 



7/ Includes 9. 578 seals marked by removing the tip of the third 

 digit on the right hind flipper and 2, 500 marked by removing the tip of 

 the second digit on the left hind flipper. 



An estimate of the size of the 1966 year class 

 based on recoveries of males that had been 

 tagged, however, was less than the estimate 

 from recoveries of animals with part of a flip- 

 per removed. Why this difference should have 

 occurred is not apparent. 



Nearly all mortality of pups on land occurs 

 before marking. Therefore, the total number 

 of pups born is estimated by adding the count 

 of dead imps to the estimate of the number of 

 pups at the time of marking (table 10). The 

 estimated number of pups born decreased from 

 643,000 in 1960 to 392,000 in 1965, then in- 

 creased to 461,000 in 196(5. The 1966 estimate, 

 however, should be considered preliminary be- 

 cause it is based only on recoveries at age 3. 



The number of pups born (exclusive of those 

 that died on land) on St. Paul Island in 1969 

 was estimated by shearing and sampling live 

 pups (Chapman and Johnson, 1968) in early 

 August (table 11). Most of the mortality on 

 land occurs before this date. 



The total number of pups born on each rook- 

 ery since 1963 was determined by adding the 

 count of dead pups to the estimate from shear- 

 ing (table 12). The estimates fluctuated mod- 

 erately around a mean of 278,000 from 1963 to 

 1966, before decreasing to 233,000 in 1969. Es- 

 timates were made for only a few selected 

 rookeries in 1967 and 1968. 



The number of pups born in 1966 was esti- 

 mated for each rookery on St. Paul and St. 



Table 10. --Estimates of the seal pup population, year classes 

 1960-66, at time of tagging, from recoveries of 

 marked male seals in ages 3 and 4, and the count 

 of dead pups, Pribilof Islands, Alaska 



Number 

 64 3, 000 

 560, 000 

 484, 000 

 446, 000 

 420, 000 

 392. 000 

 461, 000 



1_/ Estimate based on combined recoveries of males marked 

 by ta Egi"g ana by removing parts of flippers. 



15 



