Ward. — Migration of the Sockeye Salmon 393 



scanty food supply for the salmon fry. Further, that food 

 supply is apparently uniform in all parts of the stream basin 

 so that the return of the adult to a definite point does not seem 

 to be correlated with any peculiarly favorable conditions for 

 the development of the young. 



It is hardly profitable to recount further the evidence which 

 has led to the rejection of these hypotheses. They are not 

 adequate to account for the movements of the migrating sal- 

 mon since the influences are not in definite fashion coordi- 

 nated with those movements. There is one environmental 

 stimulus, however, which has shown a high degree of cor- 

 relation with the path which the red salmon follows in its 

 migration in fresh water and that is the relative temperature 

 of the different waters. This I propose to discuss more fully 

 but first wish to consider one phase of the generally recognized 

 current stimulus. In fresh water the red salmon moves con- 

 stantly up stream. While it is not influenced by the strength 

 of the current, for it may desert a strong current to follow 

 more quiet waters, yet in the largest streams it seems to modify 

 its behavior, perhaps necessarily but yet in a way to affect 

 conspicuously its distribution and incidentally its relations to 

 commercial fishing, by sticking close to the shore, or having a 

 route which follows one bank of the stream and is distinct 

 from the route along the opposite shore. 



During my last visit to Alaska I had the opportunity of 

 testing some of the working hypotheses previously formed 

 on a new type of stream. The Copper River is much larger 

 than any other stream I have previously studied in which the 

 red salmon is found, and careful attention was given to the 

 special features of the situation with a view to determining 

 the differences, if any, that characterize the migration of the 

 red salmon here in contrast with its movements in smaller 

 streams in other regions. One of the first factors which at- 

 tracted my attention was the apparent inclination of the fish 

 to migrate upstream near the banks. This was first noticed 



