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FUR-SEAL FISHERIES OF ALASKA, 1909. 
reservation is to supply young males in sufficient numbers to meet 
the heavy death rate which has been demonstrated by experience 
to occur among adult rookery bulls. The heavy mortality among 
this class of fur seals has been apparent in the steady decrease 
in the number of bulls present on rookeries during observations 
extending over ten years. To check this decrease, by providing a 
sufficient increment of young bulls, was the object of the plan of 
reserving young male seals by marking them in such manner as to 
prevent their being killed by clubbers on the sealing fields. 
During the six years from 1904 to 1909, both inclusive, 12,000 young 
males have been so reserved. Of these, 6,000 were 2-year-olds and 
6,000 3-year olds at the time of reservation. As those seals reserved 
in 1904 and 1905 now would be coming upon the rookeries as breed- 
ers, it is both interesting and desirable that we should form an idea 
of the number of these young bulls we should expect to appear upon 
the rookeries. 
Any attempt to compute the number of reserved 2-year-olds which 
might survive as breeders would be futile, the mark put upon them not 
being permanent and protecting them only for the first year. These 
2- year-olds were reserved solely for the purpose of insuring a supply 
of 3-year-olds the next year and to prevent too close killing. It was 
understood at the time the plan was inaugurated that the 2-year- 
olds would be liable to be killed the following year. Their exemp- 
tion from slaughter as 2-year-olds, however, would insure their pres- 
ence the next year as 3-year-olds, and these latter were depended 
upon to form the actual breeding reserve. For this reason, therefore, 
in attempting to compute the probable increase, only the reservation 
of 3-year-olds should be considered and not that of the 2-year-olds, 
the reservation of which acts merely as a “feeder” to that of the 
3- year-olds. 
The 3-year-olds, on the other hand, become 4-year-olds the next 
year, the killing of which is prohibited by regulation. Thereafter 
they are too large to be killed by the clubbers. Few of them, in fact, 
appear later upon the field, but instead frequent the rookery fronts 
worrying the cows. This class of young males, therefore, we may 
safely attempt to follow through succeeding years and to estimate what 
number might be expected to appear from year to year thereafter. 
INCREASE OF BULLS THROUGH RESERVATIONS. 
During the six years mentioned 6,000 3-year-olds were reserved for 
breeding, 1,000 each year. To follow their progress through the 
years following, allowance should be made for a 10 per cent mortality 
from natural causes. What mortality they suffer from pelagic seal- 
ing, although severe, need not be dealt with here, as our object merely 
