TROUT FLY-FISHING IN AMERICA 



velop the same pigment colors in all the different species 

 of trout, for if such were the case there would be no such 

 thing as any distinctive coloration of the various species 

 of trout. 



The character of the water bottom is the factor, next 

 to light, which is the one most directly responsible for the 

 many changes that take place in the coloration of trout, 

 and this is due to its direct and immediate influence upon 

 the pigment cells. 



There are three well-defined and common water bot- 

 toms which differ very markedly from each other. They 

 are known as the light bottom, the neutral bottom, and the 

 dark bottom. 



Although these different water bottoms exert different 

 influences upon the coloration of trout under the same 

 conditions of light, nevertheless the greatest effectiveness 

 of the different water bottoms is increased or diminished 

 primarily by the kind or degree of light which prevails. 



A light water bottom is one that is composed of sand 

 or gravel, or both, and has a bright appearance; a neutral 

 water bottom is one that is composed of small rocks with 

 a mixed soil or clay and has a subdued appearance which 

 leans neither to light nor dark, being gray or leadeny in 

 color ; a dark water bottom is one that is composed largely 

 of mud or very dark soils and has a dark brown or black 

 appearance. Large rocks or boulders are found on all 

 kinds of water bottoms while water vegetation is found 

 mostly on neutral and dark water bottoms, although in 



143 



