Ward. — Migration of the Sockeye Salmon 419 



supply from territory that is well furnished with ground water 

 during the early part of the summer and scantily supplied later 

 in the season, whereas other streams that have their sources 

 in snow fields or glaciers are dependent for water changes upon 

 the effect of summer temperature in melting these fields and 

 upon the area of the fields themselves, since the period of 

 abundant supply by both factors would be determined. Not 

 only each river basin but even each important tributary would 

 constitute to a considerable degree an independent problem, 

 and the record of all the facts in the case would be essential 

 for the formulation of a permanent policy regarding the preser- 

 vation of the salmon run in that stream, or of any part of it. 



Very evidently one of the serious dangers which the red 

 salmon have to face is the commercial utilization of the 

 streams which they visit. The erection of immense dams 

 and the transformation of large stretches above them into 

 reservoirs so that the water may be used for irrigation or 

 hydro-electric power, is a most serious menace to the salmon 

 runs in such a stream. In many cases it will be apparently 

 necessary to choose between the destruction of the salmon and 

 the abandonment of the project for utilizing the water in the 

 stream. This is by no means a simple problem from the stand- 

 point of general public welfare. To be sure the practice of 

 engineers seems to have omitted from consideration entirely 

 the question of the fish supply of the stream and the fact that 

 it also is valuable. Water rights have been acquired and in 

 some instances utilized without even a superficial attempt to 

 relieve the situation by constructing a fishway that might be 

 made use of by the migrating salmon.* 



In many instances, however, even the most perfect pro- 

 vision of this sort would be inadequate and it is difficult to 

 see how an effective fishway could be constructed on any plan 

 yet proposed that would surmount a dam behind which the 

 impounded water varied greatly in level. When the size and 



* For a conspicuous instance of this and the evidence associated with it, see the 

 article on the Atlantic and Pacific Salmon (Ward, 1920 a). 



