334 tr. S. BUREAU OF FISHERIES 



COMPUTATION OF FUR SEALS, PRIBILOF ISLANDS, 1929 



By Harey J. Christoffers 



The fur-seal herd of the Pribilof Islands at the present time is in 

 a very healthful condition. The large number of breeding bulls — 

 harem, idle, and surplus bulls— shows that the present requirements 

 of the herd have been amply provided for through the reserving of 

 part of the 3-year-old males for breeding purposes. It is believed 

 that at present there are not more bulls tlian are desirable. 



Though the number of breeding bulls has been greatly increased, 

 there is no apparent increase in the amount of fighting on the rook- 

 eries or in the percentage of dead pups. In spite of the increased 

 number of bulls there are still a few young bulls holding harems. 

 Many branded 9-year-olds were observed holding harems. 



In the early part of the season the large number of bulls on the 

 hauling grounds causes some trouble in making drives, especially 

 when the weather is warm. As the season advances the number of 

 bulls in drives decreases, though thej-e are always more or less of 

 them. Toward the end of the season the 2-year-olds cause more 

 trouble than the bulls. There are now so many 2-year-olds that it 

 is not advisable to drive large numbers of bachelors for any great 

 distance during the last week in July. This is, therefore, the best 

 possible time to discontinue killing and make provision for breeding 

 requirements. 



After the discontinuance of killing operations on July 23, it was 

 possible this season to mark for breeding purposes over eight thousand 

 3-year-old males before August 1. There were still a great many 

 immarked 3-,vear-olds to be observed on the hauling grounds. It is 

 felt, therefore, that sufficient 3-year-olds were reserved. With normal 

 conditions the number of 3-year-olds which could be reserved after 

 July 23 would increase each year in approximately the same pro- 

 portion as the growth of the herd. Killing operations may, therefore, 

 be discontinued at about this time each season to provide for a proper 

 reserve. 



BULLS 



The census of harem and idle bulls this season was taken on St. 

 Paul Island between July 16 and July 22, inclusive, and on St. 

 George Island on July 23 and 24. The count on Zapadni and South 

 rookeries, St. George Island, was made by Agent H. A. Peterson 

 and Storekeeper A. J. Messner. The counts on all other rookerfes, 

 on both islands, were made by Special Agent A. Christoffersen and 

 the writer. It is considered advisable for two persons to make each 

 count simultaneously so that final figures may be verified. 



Harem areas continued to expand this gcason, especially toward 

 the rear of the rookeries. A number of harems were again found on 

 hauling grounds. In a relatively few years, if the present rate of 

 expansion continues, there will be no hauling grounds on Reef rook- 

 ery, St. Paul Island. Later, when the Gorbatch hauling grounds are 

 covered with harems, the bachelors* will probably haid out on Zoltoi 

 sands. These changes would result in shortening materially the length 

 of the drives from these rookeries to the killing field. 



It was impossible, on accouat of weather conditions, to count 

 Sivutch rookery. A conservative estimate, therefore, has been 

 included. 



