2 U. S. BUREAU OF FISHERIES. 



Page. 



Black-spotted, Loch Leven, and brown trout 55 



Black-spotted trout (Salmo letvisi) 55 



Varieties and description 57 



Growth and egg production 58 



Parasites 59 



Loch Leven trout {Salmo levenensis) 60 



Description 60 



Range, size, and food 61 



Propagation 62 



Brown trout {Salmo fario) 63 



Range, size, and food 63 



Breeding habits and propagation 63 



Description 65 



Diseases common to trout under domestication and their treatment 66 



White spot disease 69 



Blue sac disease 72 



BROOK TROUT. 



The propagation of the brook trout is conducted under widely 

 differing conditions throughout the natural and acclimated range of 

 the fish. While the general principles on which the work is based 

 are essentially the same everywhere, the details connected therewith 

 must necessarily be modified to meet the varying conditions of 

 climate, water supply, location, and the purposes in view. The aim 

 of this article is to outline only those general principles, as it is 

 manifestly impossible to enter minutely into all the details that 

 would apply in any given section of the country. The material for 

 the description of the methods outlined has been drawn from wide 

 personal experience and observation. 



DESCRIPTION. 



The brook trout or speckled trout {SalveUnus fontinaUs) is one of 

 the most beautiful, active, and widely distributed of the American 

 trouts. It prefers clear, cold, rapid streams, and belongs to that 

 group of trouts known as charrs, characterized by the presence of round 

 crimson spots on the sides of the body. Other members of this class 

 are the saibling or charr {S. alpinus) of Europe and {S. stagnalis) 

 of Greenland; the red charr {S. Ma7^stoni) of eastern Canada; the 

 Sunapee trout {8. aureoJus) found in parts of New Hampshire, 

 Maine, and Vermont; the blueback trout {S. oquassa) of the Range- 

 ley Lakes in Maine, and Dolly Varden, red-spotted, or bull trout (S. 

 hairdii) of the Pacific States and Alaska. The lake trout {Gristi- 

 vomer nainaycusK) also belongs in this group. 



The general form of the brook trout's body varies considerably, 

 sometimes being elongated and sometimes rather short, but the usual 

 depth is about one-fourth or one-fifth of the length. The head is 

 large and blunt, and is contained four and one-half times in the 

 body length. The large terminal mouth is provided with teeth on 

 the jaws, tongue, and palate bones, and also with a small patch on 

 the vomer. The eye is placed high in the head; its diameter is about 

 one-sixth the length of head. The gillrakers on the first arch num- 

 ber about 17, of which 11 are on the lower arm. The scales are very 

 small and numerous; about 230 are in the lengthwise series and 35 

 above and 35 below the lateral line. The dorsal and anal rays are 

 10 and 9, respectively. The tail is square or slightly lunate in the 

 adult; forked in the young. 



