4 U. S. BUREAU OF FISHERIES. 



There is considerable variation in the color of this trout, depend- 

 ent on local conditions, sex, and age. The head, back, and sides of 

 the body, dorsal and caudal fins are of a grayish or greenish color; 

 the back, head, dorsal, and base of caudal are mottled with dark green 

 or black. Along the middle of the side are numerous round, light- 

 red spots surrounded by whitish or light-brownish circular areas. 

 The lower fins are dusky, with a pale or cream-colored anterior 

 border bounded by a black streak; remainder of fin often red in 

 breeding males. The brook trout may be distinguished from the 

 other charrs by the clark-brown or black marblings on the back and 

 the general absence of spots on the back. 



The parr marks, which are always present in young trouts and 

 salmons, are often found in large brook trout. These marks, which 

 in the brook trout are about eight in number, are large, dark, vertical 

 blotches or bars extending along the sides. 



The brook trout is closely related to the other charrs mentioned, 

 but it has quite distinct color markings and is usually less slender 

 in form. Individual brook trout, however, vary greatly in form and 

 color ; not only those of different waters, but often those of the same 

 body of water or different parts of the same lake or stream. Modifi- 

 cations of both form and color also appear during the breeding sea- 

 son. 



The brook trout exhibits such a variation in color under the vary- 

 ing conditions of sex, age, size, and locality, that it has been given 

 many local names by fishermen under the impression that it was a 

 distinct sjDecies. This variation is a protection provided by nature 

 which permits the fish to change its color and markings rapidly when 

 passing from one environment to another. The appearance of brook 

 trout under various ^jonditions of environment may be described, in 

 general, as follows: 



Slender, light-colored, and silvery in lakes, ponds, and swift 

 streams that are clear and sandy, or in parts of other bodies of water 

 where such conditions obtain. Stout and dark-colored in lakes or 

 ponds or localities of lakes or ponds having muddy bottom and con- 

 siderable vegetable growth and particularly water discolored by 

 vegetable stain. The same may be said of streams, and it may be 

 added that the swifter the flow of water where the trout occurs the 

 slenderer it is likely to be. 



As in external markings, there is likewise a great variation in the 

 color of the flesh of brook trout. Although in most instances the 

 flesh is white, trout with yellow or rich, red flesh are not rare. Sev- 

 eral reasons have been assigned as the cause for this characteristic. 

 W. C. Kendall, on page 543 of his paper on the Rangeley Lakes, Me.^ 

 gives the following as the probable cause : 



After taking everytliing into consideration it would seem that the character 

 or quantity of food influences the color of the flesh only in its fattening ef- 

 fects, and it is only the intrinsic fat or oil in the fish which produces the red 

 flesh and delicious flavor of the red-meated trout. The oil or fat is naturally 

 red as that of some other animals is naturally white or some other color, and 



=" The Rangeley Lakes, Me., with Special Reference to the Habits of the Fishes, Fish 

 CuUure, and Angliiig. By William Converse Kendall. Bulletin, U. S. Bureau of Fisheries, 

 Vol. XXXV, 19i5-16, pp. 48.5-.'594. Pis. XL-XLVI. Bureau of Fisheries Document No. 

 861, issued May 25, 1018. Washington. 



