Table 13.— Estimates of the number of pups born, based on tag 

 recoveries and the count of dead pups, year classes 1960-65, 

 Pribilof Islands, Alaska 



Table 17. — Complete counts of live pups on selected 

 rookeries in early August, St. Paul Island, 1963-67 



Rookery 



1/ Estimates are based on tag recoveries from males 

 of the year class killed at ages 3 and 4 for year classes 1960-63; 

 at age 3 for year class 1964; and at age 2 for year class 1965. 



rookeries (Tolstoi and Reef) in 1967 to elimi- 

 nate one of the major causes of disturbance on 

 the rookeries. Although we have no data to show 

 conclusively that disturbance has a lasting 

 detrimental effect, it is likely that it does. Com- 

 pared to 1966, the mean estimate of the pup 

 population increased from 27,000 to 33,500 on 

 Tolstoi and decreased from 34,900 to 31,500 

 on Reef Rookery (table 16). We concluded from 

 these data that the population did not change 

 substantially from 1966 to 1967. 



We made total counts of pups on Lukanin, 

 Kitovi, Zapadni Reef, and Little Polovina 

 Rookeries in 1967 (table 17). The 1967 counts 

 were the first on Lukanin and Kitovi Rooker- 

 ies, whereas the counts on Zapadni Reef and 

 Little Polovina have been made each year since 

 1964. For the latter two rookeries, the number 

 of pups counted in 1967 was 15 to 20 percent 

 less than the number counted in 1966. The de- 

 crease indicated by the counts may be real or 

 may have been caused by counting about 1 week 

 later than usual-- 18 August compared to about 

 10 August. Counts made later in the season are 

 inaccurate because the pups spend increasing 

 amounts of time in the water as the season 

 progresses. Counts made later than about 10 



Number 



Little Polovina.. 1,230 7,180 7,314 7,071 6,030 



Morjovi 1 - 17,530 18,384 17,388 



Zapadni Reef - 5,700 5,383 5,729 4,665 



Lukanin - - - - 3, 244 



Kitovi - - 10,307 



1 Excluding point south of Sea Lion Neck. 



August would be likely to exclude pups and 

 therefore be low. 



There is no reason to suspect that the num- 

 ber of pups born has changed appreciably since 

 1966, the last year in which all the rookeries 

 on St. Paul Island were sampled. Hence, the 

 number of pups born in 1967 was about 385,000; 

 that is, the estimated number (360,000) at time 

 of shearing in 1966, plus about 25,000 pups that 

 died before shearing. 



NUMBER OF YEARLING MALE SEALS 



The number of yearling males has been esti- 

 mated from the recovery of tags applied to 

 yearling males from the 1961, 1962, 1964, and 

 1965 year classes (table 18). The data for the 

 1961 and 1962 year classes are practically 

 complete, as very few additional recoveries 

 will be made. The 1964 and 1965 year classes 

 will yield additional recoveries. The estimated 

 number of males in the 1964 year class 

 (129,000) is considerably higher than the esti- 

 mates for the 1961 and 1962 year classes 

 (80,000). On the basis of the male kill from the 

 1964 year class at ages 2 and 3, the total num- 

 ber of males that will be killed from the year 

 class may be about 14,000 greater than that 

 from the 1962 year class. A difference of this 

 magnitude indicates that the 1964 year class 

 was stronger than the 1962 year class. Addi- 

 tional years of data are necessary to evaluate 

 the estimates derived from this method. 



The number of males that were actually 

 yearlings when tagged was determined from 



Table 16. —Estimates of the pup population on Reef and Tolstoi Rookeries, based on shearing and 

 sampling, year class 1967, Pribilof Islands, Alaska 



17 



