TABLE 33. — Estimates of fall pup population from male tag recoveries, 

 Pribilof Islands, Alaska, year classes 1958-60 



1960 



59,981 1962 



952 



130 



436,358 



■"• Douglas G. Chapman, 1961, Preliminary report on the population analysis 

 of the Pribilof fur seal herd. In Carl E. Abegglen, Alton Y. Roppel, Ancel 

 M. Johnson, and Ford Willte, Fur seal investigations, Pribilof Islands, 

 Alaska. Report of field activities J\ine - November 1961. Bureau of Com- 

 mercial Fisheries, Marine Mammal Biological Laboratory, U.S. Fish and Wild- 

 life Service, Seattle, Wash. [Processed.] 



Estimates from Tagged Females 



The fall pup population was estimated for the 

 1957 through 1960 year classes by the usual 

 method. The significantly higher tag lost to 

 tagged ratio on St. Paul Island was used to 

 correct the lower ratio on St. George Island. 

 The estimates (table 36), calculated using 

 Petersen's formula, were considerably lower 

 than those based on tag recoveries from the 

 male kill. There is no apparent explanation 

 for the difference. The fact that fewer tagged 

 females than tagged males were recovered 

 should not influence the level of the estimate. 



Tag lost to tagged ratios among females 

 killed in September on St. Paul Island were 

 very different from the ratios among females 

 taken in August. Probably, there was less 

 effort put into the identification of tag-lost 

 animals taken during the September kill. 

 Partly because of this and partly because the 



recoveries in September were insufficient as 

 a basis for a separate estimate, only the 

 returns for the period 13-24 August were 

 used in making the pup population estimates. 



Estimates of the Fall Pup Population from 

 Fall Tag Ratio 



The tag ratio of the 1962 fall pup population 

 on St. Paul Island was estimated twice by 

 counting groups of 25 pups along transect 

 lines systematically distributed on the rookery 

 areas. This method was the most promising 

 of various sampling methods tried in 1960 

 and 1961. The results of the two counts are 

 given in table 37. 



The mean of the estimates from the first 

 and second counts is 231,800 with 95 percent 

 confidence limits of +_ 53,000. 



The highest estimate of the number of pups 

 born on the Pribilof Islands in 1962 is 382,000. 



43 



