TROUT FLY-FISHING IN AMERICA 



activity of the pigment cells, but judging from my own 

 investigations, probably less than any other single ele- 

 ment. 



Mature trout have the best coloring; old trout the least 

 coloring; and young trout vary greatly in their coloring 

 but seldom, if ever, are they as highly colored as trout of 

 mature age. 



The kind or character of food eaten by trout is the 

 factor which is directly responsible for the quality and 

 quantity of the pigment colors developed, and which pro- 

 duces the marked coloration of the different species and 

 sub-species. 



All species and sub-species of trout (genus Salmo and 

 genus Salvelinus) have their own peculiar colorings, 

 which are, as a rule, distinctive. Although conditions in- 

 crease and diminish the colorings of each, their marked 

 distinctive coloration nearly always remains the same. 



Nature in the first instance determines what the col- 

 oring of each species of trout shall be by the placement of 

 the pigment cells, their size and number, as well as the 

 dominant pigment colors, which are to be developed both 

 in quality and quantity. 



The effect upon coloration of the different kinds of 

 food eaten by all species of trout seems to remain practi- 

 cally the same : that is, shrimp and all Crustacea produce 

 and develop light-colored pigments ; flies and insects, sub- 

 dued colored pigments; and worms, minnows and flesh 

 foods of all kinds, dark and rich-colored pigments. 



But these different trout foods do not produce and de- 



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