of females necessary to produce a given 

 number of pups and the recruitment needed to 

 maintain a given level of the female popula- 

 tion. 



Experimental skins now being processed will 

 make it possible to compare the relative value 

 of sealskins from males and females of vari- 

 ous ages. This information, together with in- 

 formation on the mortality of seals of each 

 age, will be used to regulate the kill so as to 

 obtain the maximum monetary value from a 

 year class of seals. 



This report summarizes the research data 

 collected on the Pribilof Islands in 1965 and 

 discusses (1) the population dynamics of the 

 seal herd, (2) the reproduction of males and 

 females, and (3) other studies. Forecasts of 

 the kill of male seals in 1966 are given in 

 appendix A. 



POPULATION 



This section presents information on tech- 

 niques used to regulate the kills of male and 

 female seals in 1965, and briefly discusses 

 research methods and results having immediate 

 application to studies of fur seal population 

 dynamics. 



Males 



Male seals of all ages, particularly those 

 age 3 and older, return to the Pribilof Islands 

 each summer. Those fronn age 1 to about age 9 

 haul out on areas adjacent to the rookeries. 

 Termed hauling grounds, -'■ these areas yield 

 the bulk of the commercial harvest of males, 

 of which more than 90 percent is made up of 

 3- and 4-year-olds. Several thousand males 

 age 9 and older haul out on traditional rookery 

 or breeding grounds where they acquire harems 

 of 1 to 100 females (average 25) each. Infor- 

 mation on the number of males of each age 

 killed commercially for their skins, and knowl- 

 edge of the number of harem and idle (reserve) 

 bulls that return to the Pribilof Islands each 

 summer is needed as a basis for managing the 

 herd. 



Commercial kill . --In 1965, nnale seals were 

 killed daily from 7 July to 9 August on St. Paul 

 Island, and on Mondays, Wednesdays, and 

 Fridays from 7 July to 6 August on St. George 

 Island. 



All available subadult males 42.0 inches 

 (106.7 cm.) long or longer (tip of nose to tip of 

 tail), but without manes, were taken on the 

 Pribilof Islands in 1965. A minimum limit of 

 body length allows most 2-year-old males to 

 escape the kill; a maximunn limit (indicated by 

 the presence of a mane) allows the recruitment 



Special terms used in this report are defined in the 

 glossary. 



of males age 6 and older into the breeding 

 reserve. Because the mane (long, silver- 

 colored guard hairs on back of the neck and on 

 the shoulders) is not evident until about age 6, 

 use of this secondary sex characteristic per- 

 mits the killing of nearly all of the available 

 3-, 4-, and 5-year-old males. 



As in previous years, the age classification 

 of males killed in 1965 was based on samples 

 of canine teeth. This information is presented 

 in appendix tables 6, 7, 8, and 9. The trend in 

 the kill of 3- and 4-year-old males is illus- 

 trated in figure 1 for St. Paul Island and in 

 figure 2 for St. George Island. Table 1 shows 

 the kill of male seals on the Pribilof Islands 

 for the 1947- 63 year classes, table 2 illustrates 

 the dates at which certain kill levels were 

 reached in the years 1954-65, and table 3 shows 

 the cumulative numbers of males killed each 

 year on St. Paul Island 1955-65. 



The minimum limit of body length was re- 

 moved on St. Paul Island 22-26 July 1965 to 

 allow a complete kill of 2-year-old males in 

 the drives. This was the second year of a 

 study designed to determine if the abundance 

 of 2-year-old males on land in late July is 

 related to the kill of 3-year-olds the following 

 year. Age and body length weredetermined for 

 20 percent of all males killed during the 5-day 

 period. 



In addition to the regular kill and the special 

 kill of 2-year-olds, 854 males larger and older 

 in appearance than those normally taken were 

 killed to test the commercial value of their 

 skins. The ages of 361 males taken 12-21 July 

 ranged from 4 through 8 (80 percent were in 

 ages 5 and 6). Age was not determined for 

 493 oversize males taken 22 July to 9 

 August. 



Beginning 27 July 1965, collection of canine 

 teeth, recovery of tags, and recording of 

 checkmarks from male seals killed on St. 

 Paul Island was transferred from the killing 

 fields to the byproducts building. Built in 1918 

 and used until 1961 as a facility for rendering 

 seal carcasses into meal and oil, the byproducts 

 building was converted in 1964 to a plant for 

 grinding and freezing carcasses of seals that 

 have been eviscerated and beheaded. The 

 ground product is used as mink food. 



In 1965, carcass-handling facilities were 

 improved by the installation of a constantly 

 moving overhead cable driven at the rate of 

 6 feet per minute by two electric motors. 

 Attached to the cable at 12-inch intervals were 

 360 long-shanked hooks. Each seal carcass 

 was suspended on a hook that passed between 

 the lower jaw bones and up through the mouth 

 (fig. 3). After the carcass was eviscerated, 

 it was washed and cooled as it moved through 

 a series of salt-water sprinklers. About 360 

 feet beyond the point where the carcass was 

 hung on a hook, a circular blade severed the 

 head and allowed the carcass to drop into a 

 high-speed grinder (fig. 4). 



