178 THE SALMON AND ITS MIGRATIONS 



ments of considerable quantities together being 

 only four or five miles per day. I have often 

 noted from day to day the progress of large bodies 

 of salmon by the catches in the nets at different 

 stations. 



After entering the rivers these conditions are 

 changed, and salmon travel mostly at night. At 

 the time when net fishing was allowed in rivers, 

 seventy-five per cent of the fish were taken during 

 the night. They move up stream very slowly, 

 much depending on the nature of the river, the 

 height of the water and the time at which they 

 first enter. Late run salmon generally ascend 

 faster, the conditions being more favorable. They 

 will frequently remain in the same pools for 

 days. Fish with peculiar marks on them, such as 

 scars, can be thus observed and the rate of pro- 

 gress noted. Where there are no natural or arti- 

 ficial obstructions on a river, salmon will ascend 

 it to its source and the same is true of its tribu- 

 taries. Very frequently these last mentioned 

 will contain the principal spawning grounds, es- 

 pecially those of large streams. The sites chosen 

 are clear gravelly bottoms with a fairly swift cur- 

 rent. Salmon will not spawn in deep sluggish 

 pools, or where the bottom is muddy or polluted 

 in any way with either sawdust or any other ma- 

 terials. I shall refer to this later on. 



When salmon first enVr a river in the spring, 

 they are in the very pink of condition and the 



