SALMON OF THE YUKON RIVER. 331 



for we learned of their occasional occurrence up the river from men who were acquainted 

 with the different species of salmon, and we observed one, a male, decidedly pink in 

 color, at Ruby on August 14, 1920, some 650 miles above the mouth of the river. 



We examined 23 specimens in 1920 on July 5, 7, 8, 9, and 13. Thirteen of these 

 were in their fifth year (see Figs. 299 and 300), having spent their first year (perhaps 15 

 months) in fresh water and having descended to the sea in their second year. The 

 scales exhibit a vigorous fresh-water growth, followed by three complete year records 

 at sea. A few of these scales, as in Figure 300, have a marginal check, which was 

 formed during the preceding winter; but a majority have at the margin from one to 

 four wide rings denoting new growth of the year. 



In addition to the individuals in their fifth year, one year of which was spent in 

 fresh water, we have eight that had remained in fresh water an additional year and were 

 maturing in their sixth year. A scale of one of the latter class is represented in Figure 

 301, the division between first and second year's growth in fresh water being clearly 

 indicated. Here, again, the growth of the new year is faintly but unmistakably shown 

 along the anterior left-hand margin of the scale. 



A third class of individuals is represented by Figure 302, these- having descended 

 to the sea soon after hatching and prior to the growth of the scale. The two salmon 

 we examined belonging to the sea type, one a male 27K inches long, the other a female 

 23>2 inches long, had matured in their fourth year, one year earlier than any of those 

 that had lingered in fresh water. 



Whether the Yukon red salmon are strays from some colony to the southward 

 or form an unflourishing local race can not be determined at present. There is no 

 reason to believe that more than one race is represented in our meager material. 



THE COHO SALMON (Oncorhynchus kisutch). 



The coho or silver salmon develops a regular run in the Yukon River, appearing 

 sparingly at the mouth of the river in the latter part of July, but the run does not show 

 any real development until in August. The Carlisle Packing Co., in 1919, packed 7 

 cases of cohos on July 14 and 3 on August 2. From August 3 to 9, 59 cases were put 

 up and in the following week 985 cases. The total pack to August 30 was 3,181 cases. 



In 1920 this species was entering the mouth of the river in very limited numbers 

 during the last week in July and does not appear in the cannery pack of that year, as 

 canning operations were discontinued before the run had developed. During the early 

 half of August, between the mouth of the river and Tanana, we found at all fishing 

 camps that occasional individuals were being taken. But we were unable to learn of 

 its occurrence in the main river above Tanana. It is well attested that the species 

 enters the Tanana and spawns in one or more tributaries of the Kantishna. How 

 generally it is distributed over the basin we were unable to ascertain. 



When the coho enters the river it is a perfectly symmetrical fish, with brilliant 

 silvery color, but in traversing the lower portion of the river it takes on a red livery, 

 and the males assume at the same time the characteristic snub-nosed appearance of 

 the breeding fish, the upper jaw becoming bluntly hooked over the lower in a manner 

 characteristic of this species. 



Scales of Yukon cohos are represented in Figures 286 to 289. As in all other coho 

 colonies that we have examined, those from the Yukon are always in their second year 

 G447°— 22 2 



