INTRODUCTION 



The year 1968 marks an important step in 

 studies of the Pribilof Islands fur seal popu- 

 lation. 



Now, 13 years after we first began to reduce 

 the seal population with the expectation that a 

 smaller population would yield larger kills and 

 more stability, we are ready to let it increase 

 in size. The high population of the 1950's has 

 been reduced and held at nearly the same level 

 since 1963. An estimate of the mean kill of 

 males from the year classes at this lower 

 population level and the size of fluctuations to 

 be expected in the kill will be determinedfrom 

 collections of data connpleted by 1972. 



The next step will be to find the productivity 

 of the population when it reaches anew, higher 

 level. 



Information about marked seals continues to 

 upset any of our previous notions about the 

 purity of separate populations in the North 

 Pacific. A small colony of seals that produced 

 young in 1968 on San Miguel Island, off the 

 coast of California, included marked animals 

 from the Pribilof and Commander Islands. A 

 male seal marked in late June 1968 on the 

 Pribilof Islands was taken on the Commander 

 Islands within a month. 



Part I, on land investigations, was prepared 

 by Raymond E. Anas, Douglas G. Chapman 

 (Director of the Center for Quantitative Analy- 

 sis, University of Washington), Ancel M. 

 Johnson, Mark C. Keyes, Alton Y. Roppel, and 

 Ford Wilke. 



Part II, on pelagic studies, was contributed 

 by Clifford H. Fiscus and Hiroshi Kajimura. 



Part I. FUR SEAL INVESTIGATIONS, PRIBILOF ISLANDS, 



ALASKA, 1968 



The purpose of fur seal research on the 

 Pribilof Islands is to appraise the reaction of 

 the herd to population levels purposely ad- 

 justed so that the level of maximum sustained 

 yield can be calculated. Part 1 of this report 

 summarizes the information collected in 1968 

 and describes the progress made toward the 

 achievement of this goal. The glossary de- 

 scribes terms having special meanings in fur 

 seal research, figures 1 and 2 show the loca- 



tion of rookeries and hauling grounds on St. 

 Paul and St. George Islands, and Appendix B 

 lists persons engaged in fur seal research on 

 the Pribilof Islands in 1968. In this report, 

 "Pribilof Islands" includes St. Paul and St. 

 George Islands and, occasionally. Sea Lion 

 Rock. There are no fur seal rookeries on 

 Walrus and Otter Islands, two of the five islands 

 belonging to the Pribilof group. 



AGE CLASSIFICATION AND NUMBER OF SEALS KILLED BY SEX 



Seals of both sexes were taken on the 

 Pribilof Islands from 26 June to 16 August 

 1968; males were killed primarily from 26 June 

 to 2 August, and females from 3 to 16 August. 



MALES 



All available males 42 inches (107 cm.) 

 long or longer from tip of nose to tip of tail, 

 but without manes, were taken from 26 June 

 to 2 August on St. Paul Island and from 26 June 

 to 5 August on St. George Island. The animals 

 were killed beginning at 6 a.m. Monday through 

 Saturday on St. Paul Island and at 9 a.m. on 

 Mondays, Wednesdays, and Fridays on St. 

 George Island. 



The lower length limit for male seals was 

 removed on St. Paul Island from 22 to 26 July 

 to continue a study of the relation of abundance 

 of seals at age 2 to the number killed from the 

 same year class a year later at age 3. 



Efforts to increase the utilization of males 

 were carried out primarily by taking as many 

 as possible of the large 4-year-olds during 



the kills of males on both islands. Seals on 

 Zapadni Point were frightened away once in 

 an attempt to make the animals haul out on an 

 area accessible to the kill. 



Table 1 gives the kills of male seals on the 

 Pribilof Islands from year classes 1947 to 

 1966. 



Right upper canine teeth collected from 20 

 percent of the males killed on the Pribilof 

 Islands in 1968 were used to estimate the age 

 composition of the total kill. A kill of 44,292 

 males in ages 2 to 6 included 35,292 taken on 

 St. Paul Island and 9,000 taken on St. George 

 Island (tables A- 1 to A-4). Ages were not de- 

 termined for an additional 1,333 young males 

 taken during the kill of females 3-16 August, 

 though most of the animals were probably 3 to 

 4 years old. The seasonal trend in the avail- 

 ability of 3- and 4-year-old males killed is 

 given in figure 3 for St. Paul Island and in 

 figure 4 for St. George Island. 



On the basis of tests of reader abilityto de- 

 termine the ages of seals from canine teeth 

 (Marine Mammal Biological Laboratory, 1969) 

 the age compositions were adjusted to show the 



