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 otf 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 sahnon 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, 

 2G: 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. Avhen 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 capture of chums were not employed until 

 tlie last week in June. For this reason, the apparent increase in size 

 of run during tlie latter days of June is certainly overemphasized by 

 the caimery 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 tlie 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 

 "silvei's" rather than as "dog salmon'' l)y fishermen of the upper 

 river. 



But changes in the appearances of the chums were soon apparent. 

 At first, as in the case of the kintr salmon, rare individuals, usually 

 males, showed themselves in an ailvanced stage of development, witn 

 brightly colored bars on the sides of the body and long hooked jaws. 

 Tliey stood out conspicuously from their fellows, which were still in 

 the " silver " stage. 



But by the last of June, 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 jaAvs 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 Ijy a further increase in the matured appearance of the fish. 

 As this occuiTed at the same time in chums and in king salmon, it 

 appeared to the fishermen that the end of the run was in sight. 



On July 7 a new run of chums suddenly set in, the great majority 

 of which were of bright silvery appearance and with no further 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 



