Ward. — Migration of the Sockeye Salmon 391 



sistent practices of the native fishermen are determined by the 

 definite movements of the fish. Moreover, however unusual 

 these movements may be, I presume we are right in assuming 

 that some factor or factors determine them definitely, since 

 they are in all cases invariable under natural conditions. 



The factors which control existing conditions are difficult 

 to determine. Whether the stream be resorted to by a single 

 run of salmon or visited by several waves, seeking different 

 spawning grounds, the conditions appear on first examination 

 to be equally complex and inexplicable. Many parts of the 

 stream that would afford apparently admirable spawning 

 grounds are never visited. One may even find cases in which 

 the spawning grounds actually visited are apparently inferior 

 in size and fitness to others on the same stream to which no 

 red salmon resort. The study of the mechanical factors that 

 might possibly be determinative has led to no definite results. 

 For such studies the multitude of short, many-branched 

 streams in southeastern Alaska offers a most profitable field 

 for study. The movements of the fish do not depend upon the 

 swiftness of the water, for they pass at times from swift water 

 into quiet, and again from a quiet stream into rapid waters. 

 The waters which they leave are sometimes shallow and some- 

 times deep in comparison with those which they choose. In 

 fact, it is not difficult to find places where the salmon turn from 

 a stream that is readily passable into one that at the moment 

 is so shallow or so obstructed that they make their way up- 

 ward with difficulty and may even be blocked for the time 

 being. So many instances of variability in these particulars 

 can be found that one is justified in concluding that the vol- 

 ume and swiftness of the stream are not determining factors in 

 directing the movements of the salmon or in leading them to 

 select one tributary above another or in preference to the main 

 stream itself. 



Once embarked upon a stream they strive constantly up- 

 ward, and yet not with equal pace. In the lower tide-influenced 

 sections of the great rivers it was observed many years ago by 



