Table 13. --Estimates of the seal pup population, year classes 1961-66 and 1969, lor St. Paul Island 



1/ 



from shearing and sampling, and for the Pribilof Islands, Alaska, from an extrapolation- 



Year class 



1961 



1962 



1963 



1964 



1965 



1966 



1969 



231,800 229,900 262,300 225,700 277,500 219,600 



47,500 34,200 22,700 41,100 22,500 13,900 



278,300 264,100 285,000 266,800 300,000 233,500 



361,800 343,300 370,500 346,800 390,000 303,500 



U Estimate for the Pribilof Islands is 1. 30 times the estimate for St. Paul Island. The factor 

 1. 30 is based on 1966 data when pup population estimates were made on all rookeries of St. Paul and 

 St. George Islands and Sea Lion Rock. 



2/ Estimates do not include the counts of dead pups. 



George Islands and Sea Lion Rock. Estimates 

 were based on shearing and sampling and 

 counts of dead pups. The proportion born on 

 St. Paul Island was 0.77. For 1961-65 and 1969 

 the number of pups born was estimated on St. 

 Paul Island only. The estimate for the Prib- 

 ilof Islands, including St. George Island and 

 Sea Lion Rock, was calculated by multiplying 

 the estimate for St. Paul Island by 1.30 (table 

 13). 



The estimated number of pups born, based 

 on tag recoveries and on shearing and sam- 

 pling, are compared in table 14 for year classes 

 1961-66. The estimates from tag recoveries 

 have always been higher than those from 

 shearing and sampling. Differences between 

 estimates from the two methods decreased from 

 over 100,000 to about 50,000 for year classes 

 born after 1963. The decrease may be par- 

 tially explained by more equitable distribution 

 of the shearing effort after 1963, which was 

 accomplished by dividing the rookeries into 

 units, recording the counts of class 3 males by 

 unit, and applying the shearing effort on the 

 basis of these counts. 



The actual number of pups born on the 

 Pribilof Islands is probably between estimates 

 from the two methods. From 1961 to 1966 

 the number of pups born decreased from nearly 

 500,000 to about 400,000. Our estimate of 



303,000 in 1969, based on shearing and sam- 

 pling, indicates that there probably has been 

 a further decrease since 1966. 



Ancel M. Johnson 



Number of Male Seals Ages 1 to 2 

 Years 



We have marked males from several recent 

 year classes when the seals were older than 



Table 14. --Comparison of estimates based on tag recoveries 

 with estimates based on shearing and sampling, 

 for number of seal pups born, year classes 1961-66, 

 Pribilof Islands, Alaska 



1/ Estimates include counts of dead pups. 



17 



