Table 21. — Estimated number of pups born, count of dead pups, 

 and number of male seals killed at ages 3 and 4, year 

 classes 1950-63, St. Paul Island 



1/ Cumulative estimates. The multiple regression is: 

 K=0.09+0.21B-0.69D 



seems desirable to use a method that does not 

 possess this disadvantage. A regression has 

 therefore been calculated based directly on the 

 counts and estimates (the data of table 21). 



For the 1964 year class, the estimated num- 

 ber of pups born (the count of dead pups plus 

 the estimate from shearing and sampling) was 

 285,000; substituting B=285, D=23 yields K= 

 44.8. Since the kill at age 3 has been 27,000, 

 the number remaining for the kill at age 4 is 

 17,800. The standard error (assuming no error 

 in the estimate of the 1964 pup population) is 

 6,400. 



Estimate of Returns Based on Estimates of 

 the Yearling Male Seal Population 



Estimates of the yearling population based 

 on recoveries of tagged seals at different ages 

 and the recent kills are shown in tables 18 and 

 22. The kill through age 4 represented 45.8 

 percent of the estimate of yearlings of the 1961 

 year class, based on recoveries at age 3; for 

 the 1962 year class the corresponding figure 

 was 39.1 percent. The average of these is 42.4 

 percent (standard error 4.8 percent). Applica- 

 tion of this percentage to the estimate of 

 yearlings from recoveries of seals at age 3 

 from the 1964 year class yields an estimated 

 total kill (ages 2 to 4) of 54,500, and hence, a 

 balance to be taken at age 4 of 24,400. The 

 standard error is 7,200. 



COMBINED ESTIMATES OF THE KILL 



OF 4-YEAR-OLD MALE SEALS ON 



ST. PAUL ISLAND 



The several estimates and their standard 

 errors are: 



Method 



Estimate Standard error 



Regression of the kill of 4- 

 year-old males on the kill 

 of 3-year-old males and the 

 mean round of the kill of 3- 

 year-old males 10,500 



Regression of returns at ages 3 

 and 4 on mean air tempera- 

 ture 4,300 



Regression of returns at ages 3 



and 4 on weights of pups 9,200 



Regression of the kill on the 

 count of dead pups and the 

 estimate of the pup population. 17,800 



Estimate of returns based on 

 estimate of the yearling popu- 

 lation 24,400 



> 1,800 



9,600 

 10,300 



> 6,400 



7,200 



The weighted average of these estimates is 

 12,700, if the standard error of the first esti- 

 mate is accepted at face value- -which gives 

 this estimate most of the weight (44 percent). 

 The unweighted average of the five estimates 

 is 13,200. We therefore estimate that 13,000 



21 



