1909.] The Life History of the Pacific Salmon. 31 



as a food fish and is practically neglected by the canneries, the Indians 

 alone finding any great use for it. 



But in addition to all these physiological changes the fish suffer many 

 mechanical injuries during the spawning operations from violent contact 

 with the stones and gravel of the bottom of the streams. Their fins be- 

 come torn and ragged and the soft skin suffers abrasions which may serve 

 as suitable growth centres for the Salmon fungus. And, finally, the 

 exertions of spawning frequently produce even more serious internal in- 

 juries, so that the spent fish is but a sorry spectacle compared with the 

 graceful creature that entered the river. 



Indeed, so exhausted are the fish from their prolonged fast and from 

 the subsequent exertions in spawning that enormous numbers of them 

 die at the conclusion of the latter process. At times the bottoms of the 

 lakes and streams in which they spawn are white with dead fish, which 

 form a grateful feast for the bears and crows. It is highly probable that 

 none of the fish that spawn in the upper reaches of the rivers ever return 

 to the sea, and since these constitute the main bulk of the run there must 

 be a very small percentage, if any, that do not die on the spawning grounds. 

 Indeed, even in the case of the Humpback and Dog salmon, which do not 

 ascend so far up the rivers, death seems to be the sequel to reproduction. 

 The difficulty does not seem to lie in any material obstacles in the way of 

 a return downstream, but in the absence of a stimulus urging the fish in 

 that direction. Evermann* describes an observation which he made at 

 Alturas Lake in Idaho, which is very pertinent in this connection. A net 

 was placed across the outlet of the lake so as to take any fish that might 

 be migrating downstream, and on September 6th the lake was found to 

 contain about one thousand salmon. By September 14th the number of 

 fish alive in the lake was reduced to two hundred and sixty-three, and by 

 September 22nd not more than twenty-five were left. Throughout this 

 time no fish were caught in the net, except a few that were in such a feeble 

 condition that they could not swim and were passively carried down by 

 the current. No fish voluntarily left the lake after the spawning period ; 

 all died on the spawning ground and this seems to be the fate of all the 

 species of Oncorhynchus. In this respect the Pacific salmon differ from 

 the Atlantic species; they spawn only once in their lifetime, the journey 

 up the river being a journey leading to the sacrifice of the individual for 

 the good of the species. 



The spawning of the Sockeye usually begins in the Fraser River in 



*Bull. U.S. Fish Commission. XVI. 1897. 



