The coefficient of multiple correlation is R = 

 0.946 (R 2 = 0.895). For the 1964 year class: 



X 1 =kill of 3-year-old males in 1965=27,000 



X 2 = mean round of the kill of 3-year-old. 

 males in 1967 = 3.43 



so that 



Y = estimated kill of 4-year-old males in 

 1968=10,500. 



The standard error (1,800) of Y = is based on 

 the assumption that X 2 is measured without 

 error. Insofar as the round system was sub- 

 stantially modified in 1967, however, the value 

 calculated for X 2 must be regarded as doubtful 

 and, despite the small standard error, less 

 weight should be attached to this forecast than 

 to the others. 



Regression of Returns at Ages 3 and 4 on 

 Mean Air Temperature and on Weights of 

 Live Pups in Autumn 



Table 20 shows the basic data for these re- 

 gressions. 



Because of the unequal lengths of the two 

 series of data, we calculated two regressions. 

 These are: 



K = 15.8+1.03T 

 K=8.33W-39.56 



For the 1964 year class: T=15 and W=9.1; the 

 two estimates are: 



Temperature Pup weight 

 regression regression 



Estimated kill at 

 ages 3 and 4 

 (combined) 



Actual kill at age 3 , 



Estimated kill at 

 age 4 



31,000 

 27,000 



4,300 



36,200 

 27,000 



9,200 



The standard errors of these estimates are 

 9,600 and 10,300, respectively. 



Regression of Kill on Count of Dead Pups 

 and Estimate of the Pup Population 



In 1966, we developed a method for fore- 

 casting based on the count of dead pups and 

 accumulative estimates of the pup population. 

 We hoped that, when available, the estimates 

 from shearing and sampling in the year of birth 

 (fall sampling estimate) could be inserted into 

 this procedure; however, the method involved 

 calculation of the percentage of returns and the 

 percentage of deaths on the islands. These 

 percentages are extremely sensitive to sam- 

 pling error in the total population estimate, 

 which appears in the denominator. Thus it 



Table 20. --The kill of 3- and 4-year-old male seals, mean air 

 temperature, and weights of pups, year classes 

 1950-63, St. Paul Island 



20 



