Pups per Harem Male 



On the basis of annual counts of harenn males 

 in mid-July and estimates of the pup popula- 

 tions from shearing and sannpling, the average 

 number of pups per harenn male has been cal- 

 culated for year classes 1963-66 on St. Paul 

 Island and for year class 1966 on St. George 

 Island. (This ratio was called "average harem" 

 until 1947.) As shown in table 20, the number 

 of pups per harem male on St. Paul Island 

 increased in 1966. 



Table 20. --Estimate of the number of pups per harem 

 male,— year classes 1963-66, Pribilof Islands, 

 Alaska 



Year 



Grand average 25. 



28. 9 



26. 4 



36. 4 



St. George Island 

 East Reef 

 East Cliff 

 North 

 South 



Staraya Artil 

 Zapadni 



Grand average 



18.7 

 40. 5 

 34. 8 

 25. 9 

 36. 3 

 31.9 



32. 8 



Although the number of pups per harenn 

 male was similar for most rookeries in 1966, 

 the ratios for a few rookeries deviated con- 

 siderably from the average. These large de- 

 viations probably reflect errors in estimates 

 of the number of pups born. 



NUMBER OF MALE YEARLINGS 



Male seals older than pups but less than 

 100 cm. long were tagged as probable yearlings 

 on St. Paul Island in 1962, 1963, 1965, and 

 1966. Because of overlap in body size between 

 seals of adjacent year classes, use of body 

 length as an indicator of age has resulted in 

 the tagging of a few 2- and 3-year-old males. 

 On the basis of recoveries of tags and deter- 

 mination of ages from canine teeth, we esti- 

 mated this error to be 2.9 percent in 1962 

 and 5.4 percent in 1963. 



On the basis of tag recoveries, the number 

 of male yearlings has been calculated for year 

 classes 1961 and 1962 (table 21). It is en- 

 couraging that the estimates (78,000) for the 

 two year classes were similar. 



Table 21. --Estimates of the population of yearling male seals based on 

 tag recoveries from male seals selected and tagged as yearlings, 

 year classes 1961-62, Pribilof Islands, Alaska 



Years Number Number 



365 78,066 



1/ Based on annual counts of harem males in mid- July 

 an"3 annual estimates of the pup populations frotn shearing 

 and sampling. 



2/ The estimate of the number of pups born on Ardiguen in 

 19^3 was included with the estimate for Gorbatch in that year. 



1964 

 1965 

 1966 



2 2.726 



3 22,745 



4 16, 030 



42 33.815 

 138 85,871 



97 



86, 099 



41, 501 



1/ N-series tags were applied in 1962 to yearling male seals born in 

 1961. and O- series tags were applied in 1963 to yearling male seals 

 born in 1962. 



2/ The total number of tags applied to males selected as yearlings on 

 the basis of body length in 1962 and 1963 were corrected according to 

 ages determined from the canine teeth of tagged animals taken in the 

 kill. 



FORECAST OF THE KILL OF MALES IN 1967 



In the past 6 years we have used several 

 methods to predict the kill of male seals on the 

 Pribilof Islands. The predictions have been 

 derived fronn: 



Method 1. Forecast of the total return of a 

 year class based on the pup population-return 

 equation developed from the population 

 dynamics model. An estimate of the size of a 

 given pup population was derived first from 

 tag recoveries at age 2, then modified when 



tag recoveries from seals of the same year 

 class became available from animals killed 

 at age 3. 



Method 2. Forecast of the kill from a year 

 class at age 4 based on: 



a. an estimate of the number of 3-year-old 



males that escaped the kill; 



b. a regression using the number of males 



killed at age 3 and the mean date of 



killing; 



24 



