130 U. S. BUREAU OF FISHERIES. 
of this theory stands the fact that no breeding ground of the red 
salmon has yet been reported from any part of the Yukon Basin. 
The breeding ground of this species could be looked for only in con- 
nection with some lake, as the red salmon will not spawn under other 
than lake conditions. And the males of the species, when on the 
spawning grounds along the shores of a lake, or in the shallows of 
the creeks which enter it, are of such brillant color as invariably to 
attract attention. It may be, therefore, that no permanent colony 
of red salmon exists in the Yukon, and that the major portion of the 
individuals observed off the mouth of the river would not enter and 
ascend the stream. Occasional individuals do, however, ascend the 
Yukon, for the writers learned of their infrequent occurrence from 
cbservers acquainted with the different species of salmon, and one 
specimen (a male, decidedly pink in color) was seen at Ruby on 
August 14. During the much longer fishing season of 1919, 20 cases 
of red salmon were packed by the cannery. 
HUMPBACK SALMON. 
The humpbacks appear at the mouth of the river more numerously 
than the red salmon, but never in sufficient numbers to constitute a 
run, even of small dimensions. It was noticeable that they were 
far advanced toward spawning in July, often with liquid milt and 
partly free eggs. It would be impossible for them to ascend the river 
far with their spawning period so close at hand. In fact, there were 
no reports of their occurrence above Andreafski, where a ripe male 
was observed on August 3. 
COHO SALMON. 
The least in value of the three principal species is the coho, which 
runs much less numerously than the other two, and, in addition, is 
the latest to appear, often not presenting itself in any numbers in 
the middle and upper reaches of the river until the ice is forming in 
the fall. This species is little dried on account of its late appearance, 
but may be fed fresh to the dogs or frozen for later consumption. It 
seems not to be highly valued for human food. 
During the season of 1920 it was entering the mouth of the river 
in very limited numbers during the last week in July, but nothing 
approximating a run had at that time developed. The individuals 
then entering were bright silvery on the sides of the body, without 
trace of the red coloration which later appears, and the jaws of the 
male had developed no hook. Later, while inspecting the fishing 
camps between the mouth of the river and Tanana, from August 2 
to 15, everywhere occasional individuals of this species were being 
taken. At Ruby on August 14 the fish wheels were catching from 
one to six cohos each day; but at the Ramparts above Tanana on 
August 20 the species had not yet put in an appearance, nor could 
anything be learned of its occurrence in the main river above Tanana 
up to the date of the party’s return from Dawson on '‘September 5. 
The individuals observed below Tanana were running principally 
along the left (south) limit of the river, and it was reported that 
their main run was always along the left bank in company with the 
bright chums (“silver”) and such king salmon as run late. To what 
