The Salmon and Trout 



colour of the outer parts than on that of the flesh; thus the more 

 variegated examples are frequently out of condition, whilst well- 

 fed individuals, with pinkish flesh, are of more uniform though 

 bright colours. 



The water has a marked influence on the colours. Trout with 

 intense ocellated spots are generally found in clear, rapid rivers 

 and in alpine pools; in the large lakes, with pebbly bottom, the fish 

 are bright silvery, and the ocellated spots are mix-ed with or replaced 

 by x-shaped black spots; in dark holes, or lakes with peaty bottom, 

 they often assume an almost uniform blackish colouration. 



Brackish or salt water has the effect of giving them a bright 

 silvery coat, with or without few spots, none of them ocellated. 



With regard to size, the various species do not present an equal 

 amount of variation. Size appears to depend upon the abundance of 

 food and the extent of the water. Thus the migratory species do not 

 appear to vary considerably in size, because they find the same condi- 

 tions in all the localities inhabited by them. A widely-spread species, 

 however, like our black-spotted trout, when it inhabits a small 

 mountain pool, with scanty food, never attains a weight of more than a 

 few ounces, while in a large lake or river, where it finds an abundance 

 of food, it reaches a weight of lo to 15 pounds. Such large trout 

 of the rivers and lakes are frequently described as salmon trout, 

 bull trout, silver trout, steelheads, etc. 



The proportions of the various parts of the body to one another 

 vary exceedingly, in the same species, with age, sex, and condition. 

 The fins vary to a certain degree. The variation in the number of 

 rays in any one genus (except Oncorhynchns) is inconsiderable and 

 of no value for specific determination. Although some species appear 

 to be characterized by comparatively low dorsal and anal fins, yet 

 the proportion of the height of these fins to their length is a rather 

 uncertain character. In most of the species the fin-rays are longer 

 during the stages of growth or development. The caudal fin 

 especially undergoes changes with age. The young of all species 

 have this fin more or less deeply incised, so that the young of a 

 species which has this fin emarginate throughout life is distinguished 

 by a deeper incision of the fin from the young of a species which 

 has it truncate in a young state. The individuals of the same 

 species do not all attain maturity at the same age or size. Finally, 

 to complete our enumeration of these variable characters, we must 

 mention that, in old males, during and after the spawning season, 



l6i 



