Fur Seal Investigations 

 Pribilof Islands, Alaska, 1964 



by 



Alton Y. Roppel, Ancel M. Johnson, 

 Raymond E. Anas, and Douglas G. Chapman 



ABSTRACT 



A total of 48,980 male seals were killed on the Pribilof Islands in 1964. Age 

 classification in percent was: 8, 60, 27, and 5, ages 2-5. The peak of the kill oc- 

 curred 27-31 July. Predicted kills of 3- and 4-year-old males on St. Paul Island 

 by 5 August were 24,000 and 13,000; actualkills were 22,203 and 10,509. Harem and 

 idle bull counts were 11,074 and 8,584. Of 16,452 female seals killed, 72 percent 

 were in ages 2-5 and 28 percent were age 6 and older. Of 147 3-year-old females 

 examined, all were nulliparous; 3 of 73 4-year-old females were primiparous and 

 post partum. Recoveries of seals marked as pups included 4,205 with tags and 1,890 

 with checkmarks only. A total of 302 seals selected and tagged as yearlings in pre- 

 vious years and 45 Soviet-tagged seals were killed. A total of 24,991 pups were 

 tagged and checkmarked. Surveys of yearlings tagged as pups in 1963 were made 

 to provide an index to survival from birth to age 1. Land pup mortality was 25,042. 

 From 4-year-old male tag recoveries, there were an estimated 614,580 pups alive 

 at the time of tagging in 1960. From 3-year-old male tag recoveries, there were 

 494,724 pups in 1961. Pup populations estimated from female data were 604,546 

 for I960 and 473,131 for 1961. Recoveries of seals tagged as yearlings indicated 

 that 80,211 male seals of the 1961 year class survived to age 1. Marked to un- 

 marked ratios yielded an estimate of 353,000 pups born on the Pribilof Islands in 

 1964. Total counts of live pups on some rookeries supported this estimate. Tagged 

 male and female pups weighed 1.10 and 0.92 kilograms less than untagged males 

 and females. A total of 1,077 skins from males and females were collected for 

 experimental use in relating economic value to age and sex. The predicted male 

 kill as of 5 August 1965 is 4,000 ages 2 and 5, 33,000 age 3, and 16,000 age 4. 



INTRODUCTION 



Complete protection of female seals was 

 one of the principles followed in restoring 

 the reduced Pribilof seal population, after 

 signing of the Fur Seal Convention of 1911. 

 The steady growth of the population from 1911 

 to about 1940 illustrated the effectiveness of 

 this principle. After 1940 the failure of the 

 kill of males and the number of harem bulls 

 to increase raised doubts about the population 

 figures in use and the wisdom of continuing 

 current management methods indefinitely. The 



Note. — Alton Y. Roppel and Ancel M. Johnson, Wildlife 

 Biologists (Research), and Raymond E. Anas, Fishery 

 Biologist (Research), Bureau of Commercial Fisheries 

 Marine Mammal Biological Laboratory, U.S. Fish and 

 Wildlife Service, Seattl* Wash.; and Douglas G. Chapman, 

 Laboratory of Statistical Research, University of Wash- 

 ington, Seattle, Wash. 



first of continuing population studies (Kenyon, 

 Scheffer, and Chapman, 1954) demonstrated 

 that the Pribilof population was far smaller 

 than had been calculated from a constant in- 

 crease percentage. The decreased growth rate 

 suggested that the seal population was being 

 restrained by one or more unknown factors 

 of its environment. A logical succeeding step 

 was a recommendation that some females be 

 killed since they did not contribute to an 

 increased population size or kill. Time was 

 needed to bring about this abrupt change in the 

 traditional standards for killing seals. The 

 first change was made in 1954 whenall females 

 found in the round-up of males were purposely 

 killed. Surprisingly, only 540 females were 

 taken by the end of the male kill on 27 July, 

 about 300 more than were usually taken acci- 

 dentally with males. 



The plan to take females was developed fur- 

 ther in 1 955 by discussions of U.S. and Japanese 



