40 FUR-SEAL FISHERIES OF ALASKA, 1909. 
NONRETURN OF COWS AFTER DISTURBANCE. 
Upon the occasion of the counting of pups on Lagoon rookery last 
summer count was made of the cows on that rookery before they were 
disturbed and driven off by the approach of the pup counters. On 
that date (August 4) 320 cows were present. Daily, for a week there- 
after, this rookery was revisited and the cows recounted, the object 
being to ascertain whether after being driven off into the water the 
cows returned to the rookery in anything like the number present 
before the disturbance. 
The series of counts made justifies the conclusion that after having 
been so disturbed the cows do not return in the same numbers as 
before the clearing off of the rookery. A list of the counts of cows 
follows : 
August 4 320 
August 5 204 
August 6 190 
August 7 164 
August 8 193 
August 9 163 
August 10 148 
August 11 152 
This shows that on the day after this rookery was first disturbed 116 
cows had failed to return and in all probability had gone to sea. At 
no time thereafter were there as many cows found on the rookery 
as when they were first driven off. We must conclude from this 
that driving off of cows from a rookery increases the number at sea 
which may be killed by pelagic sealers and that, under present con- 
ditions, disturbance of the rookeries in the manner indicated has the 
effect virtually of increasing the pelagic catch. 
CENSUS OF SEAL HERD. 
In making a census of seals in the whole herd only the adult sta- 
tioned bulls are actually counted, together with a small number of 
pups. By means of the latter an average harem is established, to be 
used in estimating the number of pups and breeding cows. This, 
however, has already been explained. All other seals in the herd 
can be enumerated only by estimation based upon such facts con- 
cerning their numbers as we may be able to gather. 
ESTIMATE OF HALF BULLS. 
Records kept of the dismissal of large seals from the killing grounds 
show that 1,770 large young males were turned away on both islands. 
Observations made heretofore by me, based upon the percentage of 
return of 3-year-old males, suggest strongly that not more than 50 
per cent of the half bulls appeared upon the hauling grounds, the 
