FISHES OF COLORADO 73 



the writer were shown to be reports of Williamson's Whitefish, Coregonus william- 

 soni Girard, which is often confused, locally, with the Grayling. 



Family SALMONIDAE 

 The Trout, Charrs, Whitefish, and Salmon 



Dorsal fin moderate, of 15 or fewer rays; adipose fin present; parietal bones 

 not meeting mesially but separated by the anterior portion of the supraoccipital 

 which joins the frontals. 



The numerous species of Salmonidae are confined to the northern two-thirds 

 of the northern hemisphere, ranging into the Arctic regions. Most of the Sal- 

 monids are fresh-water forms and even the larger species of Salmon which spend 

 a considerable portion of their lives in salt water ascend rivers to spawn. In this 

 family are included some of the best-known game fishes, the Trout and Charrs, 

 as well as other species of large commercial value. Several million pounds of the 

 Lake Whitefish, Coregonus clupeiformis (Mitchill), are taken annually from the 

 Great Lakes, and the large species of Salmon, Oncorhynchus tschawytscha (Wal- 

 baum) and related forms, which are so abundant in the Columbia River region, 

 have become the center of a large industry. 



Viewed from a purely commercial standpoint the Salmonid fishes of Colorado, 

 particularly the Trout, are the most important fishes in the state, forming a valu- 

 able natural asset. The presence of Trout in the mountain streams of Colorado 

 adds annually several thousands of dollars to the general wealth of the state. 

 The additional value of these fishes to the residents of the state cannot be reckoned 

 so easily but it is certainly large, so that the care of the Trout and their artificial 

 propagation well repay the funds so invested. 



Four genera of Salmonidae are represented in Colorado by either native or 

 introduced species, or both. Three of these genera are so closely related that 

 technical characters must be used for their separation, although the markings and 

 colors of the Colorado species are added to facilitate rapid determination. The 

 young of most species of Salmonids are marked with several vertical, dusky bars, 

 known as "parr marks. "^ These parr marks gradually disappear as the fish 

 grows older, although they may persist in almost full-grown individuals, and are 

 not to be confused with the black spots mentioned in the key. 



a. Jaws usually without teeth; teeth if present extremely minute; scales rather prominent; 

 lower jaw shorter than the upper by which it is partly included; Colorado species silvery, 

 bluish above, without spots, fins margined with black, parr marks only in the young. 



Coregonus (Artedi) Linnaeus, p. 74 

 aa. Jaws strongly toothed; scales small, often more or less obscure; species spotted with black; 

 parr marks persisting in rather large individuals. 



■ See Fig. 37. 



