68 XX. S. BUREAU OF FISHERIES 



reserved may not be larger than necessary. With an average harem 

 of about 40 it seems certain that all females arriving during the 

 rookery breeding period are being properly served. 



The virgin females arriving after the rookery breeding period is 

 practically over are for the most part taken care of near the end of 

 the season by the surplus and young bulls that have not held harems 

 or were in the idle bull class. These bulls are strong and virile, while 

 the older bulls wliich have been holding harems throughout the season 

 are ready to retire before the virgin cows arrive. It is necessary, 

 therefore, that personal observations be made in order to determine 

 whether sufficient surplus bidls have been reserved to take care of 

 the virgin females. 



Wlien there is an average harem of less than 40 females, and at 

 the same time a large number of idle and surplus bulls, the breeding 

 bulls do not retain their positions throughout the entire season. The 

 stronger members of the idle and surplus bull class replace the harem 

 bulls as soon as the latter begin to weaken. Tliis does not necessarily 

 mean that the replaced harem bull is not still able to procreate. If 

 stiU strong and virile, he usually does not retire any farther than the 

 hauling grounds or the rear of the rookery, where he is able to secure 

 transient females. 



In 1934, a total of 51,935 animals classed as 3-year-olds were killed, 

 as compared with 52,747 in 1933. Tliis decrease in the total number 

 of 3-year-old males secured was undoubtedly due to the continual 

 stormy weather, accompanied b}^ heavy driving rains, which pre- 

 vailed throughout the season. 



The captain of the Penguin reported that large numbers of seals 

 were in Ikatan Bay about July 20, and the captain of a Coast Guard 

 cutter gave a similar report with respect to Akutan Bay. When 

 conditions are favorable at the islands, seals do not usually remain 

 for any considerable time around the Aleutians. The 3-year-old 

 males have no particular reason for going to the Pribilof Islands, as 

 they are not of breeding age. When they do arrive, they like to 

 haul out and sleep and play. Warm foggy weather is favorable for 

 the hauHng out of bachelors, while driving rain storms cause them to 

 return to the water. 



If weather conditions had been favorable, a shortage of 3-year-old 

 males would have indicated an abnormal death rate at sea. As 

 stormy weather prevailed throughout the entire season, however, it 

 was impossible to determine whether there was an actual shortage 

 of seals. It may be assumed that there was a normal increase in the 

 rtumber of killable seals, but because of adverse weather they did not 

 arrive at the islands. 



An annual increase of approximately 8 percent in the past does not 

 necessarily signify that this rate wiU continue as the herd increases 

 in size. In some years there may be more than the average number 

 of natural enemies of the seals at sea. If the natural enemies increase 

 at the same rate as the herd, the death rate at sea would remain about 

 constant. If the natural enemies increase at a lower rate, then it 

 would soon be possible to have abnormally increased killings in a 

 year or a series of years. It appears that a series of years in which 

 there is a large increase may be followed by a series of years when the 

 growth of the herd is at a standstill, gradually preparing for another 

 period of forging ahead. 



