8 



TJ. S. BUREAU OF FISHERIES. 



stantial runs in the Yukon River (king, chum, and coho), and of 

 these king and chum are of the greatest importance by far. The 

 few reds or sockeyes taken near the mouth of the river are perhaps 

 strays, for no breeding has yet been reported from any part of the 

 Yukon Basin. 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. As they were far ad- 

 vanced toward spawning in July, it was evidently impossible that 

 they could ascend the river far with their spawning period so close 

 at hand. The coho runs more or less numerously than the king or 

 chum salmon and in addition is the latest to appear, often not pre- 

 senting itself in any numbers in the middle and upper reaches of 

 the river until the ice is forming in the fall. 



The king salmon begins running in the last week of May or the 

 early days of J une. The run culminates quickly and then almost as 

 quickly declines. The rate of migration was found to be remarkably 

 high, the average rate of travel from Tanana to Dawson being 

 slightly less than 45 miles per day, and from Pilot station to Daw- 

 son, involving practically the entire length of the river below Daw- 

 son, the average rate was 57 miles per day. No record of any other 

 river approaches this in completeness, nor in the high rate of travel 

 indicated. This unexampled speed with which salmon ascend the 

 Yukon is doubtless associated with the great distances to be traversed 

 before reaching their upper spawning areas, taken in connection with 

 the shortness of the summer season. 



The most important natural enemies of the king salmon are the 

 white whales, or belugas, and the lamprey eels, the former being 

 undoubtedly exceedingly destructive, while the latter, though caus- 

 ing scars on the fish in much greater abundance than in any other 

 river, as observed by investigators, do not appear to effect serious 

 injury to the fish. 



The chum salmon, which is the principal food product of the 

 Yukon River, made its appsarance but a few days later than the 

 advent of the king salmon, the rate of migration being approxi- 

 mately the same as that of the king. 



Two phases in the development of the chum salmon are distin- 

 guished by the natives under the names of " dog salmon " and " silver 

 salmon," the dog salmon comprising the individuals furthest ad- 

 vanced toward spawning. In general the " dog salmon " along any 

 stretch of the river consist of those individuals which will turn into 

 some adjacent tributary to spawn, while the "silvers" are on their 

 way to the upper reaches of the river, show relatively little of the 

 sexual changes they will exhibit on their spawning beds, and are 

 still richly provided with the oil which serves as fuel and the princi- 

 pal source of nourishment during the long journey still before them. 



" Dogs " and " silvers " were in general keeping apart from each 

 other and following distinct migration routes, the ".dogs " pre- 

 dominating on the right and the " silvers " on the left side of the 

 stream. Heavier runs of kings and cohos were found in company 

 with the " silvers " along the left limit of the river. It appears, 

 therefore, that there is a prevailing use of the left shore by those fish 

 which are found in the upper reaches of the river. This may have 



