ALASKA FISHERY AND FUR-SEAL INDUSTRIES, 1920. 135 
chum or dog salmon, which must be considered the principal food © 
product of the Yukon River. 
It makes its appearance off the mouth of the river only a few days 
later than the advent of the king salmon. In 1920 the first chum was 
obtained June 17, and from the 17th to the 19th, 138 became entangled 
in the coarse mesh of the king salmon nets set outside the mouth of 
the river; but none apparently had as yet entered the stream. On 
June 20, 2 were reported inside the river; June 21, 82; and June 22, 
26; but ‘during these three days 856 were taken in the outside nets, 
indicating clearly that the chums were beginning to school in some 
abundance outside the river, but that few were entering up to June 
22, when the run up the river may be said to have begun. It became 
greatly accelerated on June 29 and maintained itself with minor 
fluctuations, until the cannery ceased operations the middle of July. 
No strictly ‘quantitative results concerning the run of chums could 
be obtained from the cannery records during this season, as nets 
with appropriate mesh for ¢ apture of chums were not employ ed until 
the last week in June. For this reason, the apparent increase in size 
of run during the latter days of June is certainly overemphasized by 
‘the cannery statistics. 
The first chums to arrive were further advanced toward sexual 
maturity than were the king salmon. In the latter the testes and 
ovaries were small and the snout so little produced in the males that 
there was no certain external evidence of the sex of the individuals 
examined. But in the case of the chums, even those earliest to run 
had the milt white in color and obviously enlarged, and the large eggs 
were already loosening in the ovary. The jaws of the males were not 
hooked, but were showing a slight sharpening and elongation, so that 
sex determination could ‘usually be made from the appearance of the 
head. All the early chums were bright silvery in color, with abun- 
dant oil, and pinkish flesh which turned a deeper red on drying. All 
of them were in such condition that they would have been classed as 
“silvers” rather than as “dog salmon” by fishermen of the upper 
river. 
But changes in the appearances of the chums were soon apparent. 
At first, as in the case of the king salmon, rare individuals, usually 
males, showed themselves in an advanced stage of dev elopment, with 
brightly colored bars on the sides of the body and long hooked jaws. 
They stood out conspicuously from their fellows, which were still in 
the “ silver ” stage. 
But by the last of J une, when a great increase suddenly occurred 
in the take of chum salmon, obvious seasonal changes had appeared 
in this species, as in the king salmon running at the same period. It 
was now the rule for the males to exhibit elongated jaws provided 
with canine teeth, and to show the beginnings of the conspicuous 
color marks which characterize the spawning males of this species. 
During the first days of July the run of chums again fell off, accom- 
panied by a further increase in the matured appearance of the fish. 
As this occurred at the same time in chums and in king salmon, it 
appeared to the fishermen that the end of the run was in ‘sight. 
n July 7 a new run of chums suddenly set in, the oreat majority 
of which were of bright silvery appearance and with no further s sea- 
sonal advancement than had been shown by the fish that ran first in 
June. Among them were a few stragglers of the previous run, the 
