3I« BULLETIN OF THE BUREAU OF FISHERIES. 



Three of the five species of salmon that occur along the Pacific shores of North 

 America enter the Yukon Basin in sufficient numbers to constitute distinct runs. These 

 are the king or chinook salmon, the chum or dog salmon, and the coho or silver salmon. 

 The names here given are those by which these species are known in other districts of 

 Alaska and generally along the coast to the southward. Unfortunately, in the Yukon 

 Basin, there is confusion in this regard. The coho or silver salmon is most frequently 

 called chinook, while the various grades of the chum or dog salmon are known as "silvers," 

 "half-breeds," and "dogs." The king salmon alone, of the three species that ascend 

 the river in numbers, is called by the same name by which it is elsewhere designated. 



The two remaining species of Pacific coast salmon, the humpback and the sockeye 

 or red salmon, enter the river each year in small numbers and have no economic impor- 

 tance. To what extent the individuals of these species may be strays from other streams 

 that have well-defined runs has not been determined. 



The material on which the present paper is based was obtained from June 15 to 

 July 31, 1920, at the cannery of the Carlisle Packing Co., located in the entrance to 

 Kwiguk Channel, a branch of the Kwikluak or South Mouth of the Yukon. 



THE KING SALMON (Oncorhynchus tschawytscha) . 



The king salmon is the most highly prized for human consumption of the three 



Yukon species. It is also valued for dog feed, especially in the upper course of the river, 



for by the time the salmon have fought their way upstream a thousand miles or more even 



the richest species contains no more oil than is needed to furnish satisfactory dog feed. 



As it enters the mouth of the river, the Yukon king is the richest salmon known to us. 



It there drips oil profusely when hung on the racks to dry and is, in fact, too rich for most 



successful canning. The canned product, if handled roughly, or if shipped to distant 



points, is in danger of breaking down to a substance of mushlike consistency. King 



salmon taken at some point higher up the river, where a portion of the oil would have 



been expended during the ascent, would in this respect furnish a better commercial 



product. 



RATE OF TRAVEL. 



The run begins at the mouth of the river in the latter part of May or early in June, 

 almost as soon as the river is clear of ice after the spring break-up ; and it lasts as a com- 

 mercially valuable run for about three weeks. Tradition has it the king salmon appear at 

 points as high as Tanana and the Ramparts at the same time as the first steamer that 

 ascends the river from St. Michaels on the opening of navigation. This would indicate 

 an unprecedentedly high rate of travel in a river with very swift current. Such incom- 

 plete data as we have concerning the ascent of salmon in other rivers indicate a rate not 

 to exceed 10 to 20 miles per day. But in the Yukon Basin the distances to be traversed 

 are great — some of the spawning beds being 2,000 to 3,000 miles from the sea — -and the 

 summer season is much shorter than in any other large salmon river. These two factors 

 necessitate a high rate of speed in ascending the river, and the fact that this has been de- 

 veloped in the Yukon salmon is one more instance of close adaptation to the conditions of 

 their environment on the part of a highly localized race. Rapid ascent of a river means 

 expenditure of energy out of all proportion to the distance to be traversed. Unusual 

 stores of potential energy in the form of oil are therefore required by the Yukon salmon. 

 We have already referred to the unusually rich provision of oil in the case of the king 



