the residents of the Pribilof Islands to use as food. 

 Commercial kiUing for skins was resumed in 1918 

 after the 6-year cessation. From 1918 to 1922, 

 harvests of seals were high in relation to pop- 

 ulation size because of the accumulation of males. 

 The kill declined after these were removed, but 

 thereafter steadily increased until 1940. From 

 1940 to 1955, it averaged about 66,000 males 

 annually. Since then, male production has varied 

 from a high of 96,000 in 1956 to a low of 30,000 

 in 1959. Part of the difference between these 

 extremes resulted from an extended season in 1956 

 which made available a larger proportion of the 

 3-year-old class, but recent fluctuations are caused 

 primarily by variations in year class survival. 



In the management of the fur seal herd, the 

 Federal Government has adhered to a policy of 

 taking pelts from seals considered surplus to 

 breeding requirements. From 1923 to 1932, a 

 minimum yearly breeding reserve of several 

 thousand bachelors was provided by marking them 

 with a brand or by shearing a patch of fur, then 

 permitting them to return to the sea. This pre- 

 caution may not have been necessary, but it in- 

 sured that the number of males escaping the kill 

 would be adequate. 



From 1932 to 1955, a sufficient breeding stock 

 was assured by limiting the killing season each 

 year to a selected period from about the middle 

 of June to the end of July. Only the male seals 

 41 to 45 inches long were taken as they appeared 

 in the daily drives on the islands during the 

 sealing season. From one-half to two-thirds of 

 the animals in this group are 3 years old, and 

 most of the rem.ainder are 4 years old; a small 

 number of 2- and 5-year-old males are included. 

 The proportion of 3- and 4-year-old animals 

 taken depends on the relative survival of year 

 classes. 



In recent years the sealing season has been 

 adjusted to the number of young males that are 

 available and to some extent to the age and size 

 of seals that are wanted. Early seasons produce a 



larger proportion of 4-year-old seals and later 

 seasons a larger proportion of 3-year-old seals, 

 since they arrive in order of age. Currently, 

 the season for male seals begins on 2 July and 

 ends on 5 August. Close cropping of 3-year-old 

 seals during a late season leaves relatively few 

 4-year-old males to be taken early in the following 

 year. Forecasts of year class strength made be- 

 fore the 3-year-old seals appear in the kill are 

 still inaccurate. Therefore, exact advance plan- 

 ning for harvests of a given size is not possible. 



The number of males that have been escaping 

 the kill is considered to be more than adequate. 

 As a result, the upper size limit of harvestable 

 male seals has been increased recently. This 

 change permits closer cropping by taking animals 

 that would have been rejected solely because of 

 size under the former limit even though they 

 had skins of good quality. It also compensates 

 for the change in the method of measuring length. 

 Length is now measured from nose to tip of tail 

 rather than from nose to base of tail. 



Failure of the harem bulls and the male kill to 

 increase in number after 1940 caused biologists 

 to conclude by 1952 that the herd had reached, 

 or was near, its peak of development. One major 

 factor that precludes further possible growth of 

 the herd is the limited food supply available to 

 the nursing females in the summer and to the 

 pups during their first months at sea in the fall. 

 Estimates of the number of pups born, based on 

 tag recoveries, indicate that production is high 

 but that survival to age 3 is now much more 

 variable than when the herd was smaller and 

 growing rapidly. On the basis of experience 

 with other animal populations and on calcula- 

 tions of the relation of pups born to the return 

 of males at age 3, it is believed that the max- 

 imum sustainable yield can be achieved from, 

 a fur seal herd that produces about 500,000 

 pups annually. The adult female component 

 of the herd has been undergoing reduction 

 since 1956 in order to bring it to a level that 

 will produce this optimum number of pups. 



14 



