130 American Fisheries Society 



by the impulse to seek water richer in oxygen, but such must be 

 a subordinate factor for salmon may pass several seasons con- 

 tinuously in the sea. 



Salmon Rarely Captured at Sea. 



The migration of Salmon presents many facts which impress 

 the scientist as profoundly as the ordinary observer. The sea 

 at various depths is ransacked by man's engines of destruction, 

 and the feeding resorts of the salmon are probably at considerable 

 depths, or the fish would be taken more frequently than they are, 

 in nets and on hooks, used on a vast scale by hundreds of thousands 

 of sea fishermen. Occasionally a salmon is taken in the ocean, but 

 such captures are rare, even in an area like the Gulf of St. Lawrence, 

 into which empty between 50 and 60 famous salmon rivers. 



Apparently the vast schools of salmon, which scatter in the 

 ocean after leaving the rivers of this continent, and of northern 

 Europe and Asia, descend beyond the reach of the gear so 

 plentifully strewn over every sea, and elude the observation of 

 scientists and of all who fare upon the deep. 



Temperature Extremes Deter Ascent. 



Salmon migrate into fresh water at regular seasons of the year, 

 indeed, a leading canner in British Columbia finds, from a record 

 kept for a great number of years, that the date is almost uniform, 

 varying only a day or two from year to year for the main "July 

 run" of Sockeyes. On reaching the estuary, Salmon often linger 

 as if to accustom themselves to brackish and fresh water conditions. 

 A temperature too cold, or too warm, a dry season with low water 

 in the river may detain them, but with the descent of an abundant 

 flood of cool water, due to rains or melting snow, the salmon 

 schools cannot be restrained. 



Time and Length of Ascent. 



Once fairly in the river nothing can daunt them. The ascent 

 may cover many weeks or even months, the early runs in May or 

 June will linger longer on the way than the latter schools in August, 

 September, or October, while, in some Pacific rivers, Salmon which 

 ascend in November and December migrate most rapidly of all. 

 Ten, fifteen, or twenty days, may suffice; but such species as the 



