THEORY AND PRACTICE 53 



when they leave the mouth of the river, nor 

 where they dwell during the winter months, 

 it is difficult to decide what they feed on. 

 One thing is plain, a full-grown salmon is a 

 square-tailed fish and therefore is a bottom 

 feeder. 



It seems certain that salmon have a sense 

 of colour. Experiments have been made in 

 aquariums that prove conclusively that fish 

 can distinguish one colour from another. 



Many male fish are of very gaudy colours, 

 supposedly for the purpose of attracting 

 the females, and some fish, the flounders for 

 example, have the power of changing their 

 colours to suit their environment. These 

 things would hardly be if fish were colour 

 blind, yet I hardly believe that salmon are 

 sensitive to slight variations of colour, not- 

 withstanding that flies that are successful 

 on one river may fail when used on another 

 stream. 



Some writers have pointed out that the 

 prevailing colour of the bottom of a pool 

 affects the coloration of the fly and that it 



