Table 22. — Mean estimates of the seal pup population, year 

 classes 1966 and 1968, from shearing and sampling on 

 selected rookeries, St. Paul Island 



Rooker 



Mean estimate 



1966 



1968 



been born on Morjovi and 8 percent fewer on 

 Zapadni Reef Rookeries since 1966. 



Beginning in 1963 the annual kill of females 

 has been adjusted to maintain a constant level 

 of pup production; however, the production of 

 pups may have descreased slightly since then. 

 Recent estimates of the pup population from 

 recoveries of marked seals have declined 

 steadily and have not varied as they did for 

 year classes 1955-59. The estimates maybe 

 slightly inflated by tag-caused mortality and 

 are, in fact, higher than estimates from shear- 

 ing and sampling in the summer of birth. Con- 

 fidence limits have not been calculated be- 

 cause we believe that the estimates are biased 

 and, therefore, the limits would not reflect the 

 true confidence level. Perhaps we can accept 

 the estimate of the nunnber of pups born from 

 recoveries of animals given tags or other 

 marks as the upper limit and the estimate 

 based on shearing and sampling as the lower 

 limit, and assume that the actual number is 

 between the two estimates. For example, the 

 limits for the 1965 year class are 400,000 and 

 350,000, rounded to the nearest 10,000. The 



number of pups born in 1968 is probably within 

 this range also. 



NUMBER OF YEARLING MALE SEALS 



Recoveries of yearling seals tagged in 

 autumn have been used to estimate the size of 

 a year class at age 1, and 1968 was the first 

 year in which sufficient data from the re- 

 covery of males tagged at age Z or older be- 

 came available for evaluating survival beyond 

 age 1. 



The survival to age 1 of seals born in 1964-66 

 was estimated from tags recoveredfrom males 

 selected by body length and tagged as yearlings 

 in 1965-67. The true age of each seal recovered 

 in the kill was determined from a canine tooth. 

 The age composition was then used to estimate 

 the actual number of yearlings that were 

 tagged. For example, of 873 males tagged as 

 yearlings in 1965, 64 were known yearlings 

 (tagged as pups) from the 1964 year class 

 and 809 were considered to be yearlings on 

 the basis of their length (see section on year- 

 ling tagging). Of 294 seals selected as year- 

 lings and later recovered, Z\ were 2-year-olds 

 (1963 year class) and 273 were yearlings 

 (1964 year class) when tagged. Therefore, the 

 estimated number of males that were actually 

 yearlings from the 1964 year class when tagged 

 in 1965 was 815; that is, 64 + (273/294)809. 



The number of tagged seals recovered was 

 adjusted to include animals of unknownage and 

 those that had lost both tags (table 24). Animals 

 of unknown age that could be identified as be- 

 longing to a given tag series were allotted by 

 age according to the observed age of animals 

 selected for tagging and recovered in the kill. 

 Seals that lost both tags and could not be identi- 

 fied as to the year tagged were allotted ac- 

 cording to the number of tags recovered for 



Table 23. --Complete coionts of living seal pups on selected rookeries in early 

 August, St. Paul Island, 1963-68 



Rooker\ 



1963 1964 



1965 1966 



1967 



1968 



-Number- 



Morjovi — 



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



--- 17, 530 18, 384 17, 388 



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



Lukanin — - 3,244 



Kitovi 10, 307 



16, 781 

 5, 916 



y The pups on a small rookery south of Sea Lion Neck were not counted. 



19 



