150 THE FUR SEALS OF THE PRIBILOF ISLANDS. 
struggles on the rookeries. The sole artificial loss to which the herd has been sub- 
jected is that resulting from pelagic sealing. We may assume that the natural losses 
of the herd were in these early days, as now, constant and uniform. With the small 
added loss resulting from pelagic sealing they balanced the gain of the herd due to the 
influx of young breeders. It may be that the loss entailed by the pelagic catch was 
the final determining check on the herd’s increase. As we have seen, in the last year 
of the period we are considering, this pelagic catch was trebled. 
PERIOD SUBSEQUENT TO 1882. 
If now we take into consideration the period subsequent to 1882 we find that this 
increase in the pelagic catch was maintained and steadily augmented until at its 
maximum in the year 1894 it exceeded by twelve times the normal size of the catch in 
the former period of equilibrium. On the other hand, we find the Jand catch which was 
maintained at its normal rate until the year 1889, suddenly fell to one-fifth its size in 
1890, and has remained there since. 
EXPANSION OF PELAGIC, DECREASE OF LAND SEALING. 
From a study of these statistics two important facts are made clear: First, that 
there has been since 1880 an enormous expansion of pelagic sealing; second, that there 
has been in the same period a marked decrease in the product of land sealing. From 
what we know of the nature of the two industries and their effect on the herd we are 
prepared to find these two facts related to each other as cause and effect. 
We need not repeat here the proof that land killing has had nothing to do with 
the decline of the herd. It must be pointed out, however, that land killing is strictly 
dependent upon the condition of the breeding herd. The quota of any given year 
represents the male animals which survive to the age of three years from a given 
birthrate. As the quota of males is, so will be the increment of young breeders which 
the herd receives. A diminished quota therefore means a diminished gain to the 
breeding herd for the same year. 
CAUSE OF DECREASE TO BE SOUGHT IN THE BREEDING HERD. 
Naturally, the cause of any diminution in the supply of killable seals must be 
sought for in the condition of the breeding herd three years previous. From this fact 
it becomes apparent that for the cause of the enormous reduction in the bachelor herd 
seen in the quota of 1890 we must look back to the year 1887, and inasmuch as the 
decline in the bachelor herd was great and alarming in 1890, the depletion of the 
breeding herd in 1887, when the seals for this quota were born, must have been equally 
great and striking. The date of the decline in the herd must, therefore, fall prior to 
the year 1887. 
* From what has been said about the relation of the bachelor herd to the breeding 
herd it must also be plain that no serious diminution had occurred in the birth rate 
prior to 1882, else it would not have been possible to maintain, as was done until 1889, 
by any possible means the killing of 100,000 animals of no matter what age or size. 
THE BEGINNING OF THE DECLINE. 
We may therefore assume that the decrease in the breeding herd began some- 
where between 1880 and 1887. It is impossible to locate the exact date. We have 
