NORTH AMERICAN SALMONIDAE 



263 



The final rankings, by species and genus, accord- 

 ing to distribution in cold waters, are as follows: 



Crisiivomer and f^nlveUnu-s ai'e arctic and sub- 

 arctic genera, except that <*<'. fontinalix, which dif- 

 fers most widely from the other species of 

 Salvelimts in respect to other characteristics is 

 more southerly. All Oncorhyiichus species range 

 far to the north, but t-ihairytscha and kisutch are 

 more tolerant than tlie others of warmer water. 

 Salmo saJar lives in colder water than either of 

 the Pacific species of Salmo. The range of clarki 

 is peculiar in that it extends neither far to the 

 north nor far to the south, but inhabits the tem- 

 perate waters between. While it extends to 

 Bristol Bay, gairdneri avoids the colder streams 

 and extends into much warmer waters than any of 

 the other species. 



COMPARISON OF NORTH AMERICAN AND 

 ASIATIC GENERA 



Some authors classify the salmons and trouts, 

 together with the graylings and whitefishes, in a 

 single family, which they call Salmonidae. We 

 prefer to consider them as three families, the Thy- 

 mallidae, Coregonidae, and Salmonidae. The last 

 is the gi-oup discussed below. 



In addition to the genera of Salmonidae that 

 occur in North America two fresh-water genera 

 occur only in Asia (Dymond and Vladykov, 1934). 

 Brachijmyxtao) occurs across Siberia and south to 

 the rivers of Japan and the Okhotsk Sea. Hucho 

 consists of tliree species, one on the Danube, one in 

 the rivers of Siberia, and a third in Sakhalin and 



the rivei-s entering the Okhotsk Sea (Dymond and 

 Vladykov, 1934). 



Some notion of the relationship between these 

 two purely Asiatic genera and tiie other four gen- 

 era is obtained by comparing their osteology since 

 other characteristics are not sufficiently well-docu- 

 mented for tlie Asiatic genera. Furthermore, 

 morphological material is chiefly available for only 

 one or two species of each genus. The available 

 osteological data are well summarized by Norden 

 (1958). As Norden classed Cristivomer under 

 SalreJimis and used Cristivomer namaycu-^h as his 

 chief representative of Salvelinus, we are forced to 

 combine these two genera for the purpose of this 

 comparison ( table 32 ) . 



Table 32. — Comparison of certain generic characteristics 

 in Salmonidae 



[Osteological characters adapted from Norden, 1958] 



The number of ditferences between genera in 

 ten characters (from table 32) are siunmarized 

 in table 33. 



The relationships between genera based only 

 on the 10 characters of table 32 are depicted in 

 figure 18, in which the distances between genera 

 are roughly proportional to the number of differ- 

 ences in characters ( from table 33) . 



