Ward. — Migration of the Sockeye Salmon 423 



the species, but the data are involved and scanty and it would 

 be venturesome at the present to maintain that the experimen- 

 tal evidence is really sufficient to establish the possibility of 

 thus modifying the habits of fish. 



It has occurred to me as a very interesting possibility that 

 the physical conditions, especially as regards the temperature 

 of water, might be so radically modified by the erection of 

 a great dam, and impounding of a vast area of water, that 

 as a result the fish would find at some junction point in the 

 stream different relative temperature conditions from those 

 that had existed previous to the erection of the dam and the 

 creation of the reservoir. If conditions should be thus changed 

 and the views which I have advanced concerning the directive 

 influence of temperature be correct, then the migration path 

 would be changed, naturally as it were, and the fish would 

 follow to parts of the stream which they had never visited 

 before. 



I have devoted considerable time and space to the analysis 

 of the problems presented by the erection of dams since I be- 

 lieve it to be the most serious and immediate danger which 

 faces the salmon in fresh water in some regions. Overfishing 

 can be regulated by law and the run of salmon brought back 

 to a normal level, or at least very greatly increased so that 

 in my opinion the fished-out streams on the Pacific Coast can 

 be restored by appropriate measures. In making this predic- 

 tion, I am not unmindful of the fact that in the United States 

 and particularly in Alaska the laws governing the fisheries are 

 "obsolete and inadequate," and their enforcement is quite 

 difficult. But some day and most unexpectedly the tide will 

 turn and under sane control the salmon run in those depleted 

 streams will be nursed back to life. Stream pollution, also, 

 which now seems to be at its maximum, will be corrected and 

 aquatic habitats will slowly return to a normal condition. But 

 the wave of development which is just beginning to affect 

 broadly the water power possibilities of the country will bring 

 rapidly changes that are permanent and so radical that unless 



