Salmonidas 63 



and rarely enter streams except to spawn. In far northern 

 regions they often descend to the sea; but in the latitude of the 

 United States this is never possible for them, as they are unable 

 to endure warm or impure water. They seldom take the hook, 

 and rarely feed on other fishes. Numerous local varieties char- 

 acterize the lakes of Scandinavia, Scotland, and Arctic Asia 

 and America. Largest and most desirable of all these as a 

 food-fish is the common whitefish of the Great Lakes (Coregonus 

 clupeiformis) , with its allies or variants in the Mackenzie and 

 Yukon. 



The species of Coregonus differ from each other in the form 

 and size of the mouth, in the form of the body, and in the de- 

 velopment of the gill-rakers. 



Coregonus oxyrhynchus the Schnabel of Holland, Germany, 

 and Scandinavia has the mouth very small, the sharp snout 

 projecting far beyond it. No species similar to this is found 

 in America. 



The Rocky Mountain whitefish (Coregonus williamsoni) has 

 also a small mouth and projecting snout, but the latter is blunter 



FIG. 49. Rocky Mountain Whitefish, Coregonus williamsoni Girard. 



and much shorter than in C. oxyrhynchus. This is a small 

 species abounding everywhere in the clear lakes and streams of 

 the Rocky Mountains and the Sierra Nevada, from Colorado to 

 Vancouver Island. It is a handsome fish and excellent as food. 

 Closely allied to Coregonus williamsoni is the pilot-fish, 

 shad-waiter, roundfish, or Menomonee whitefish (Coregonus 

 quadrilaterals). This species is found in the Great Lakes, the 

 Adirondack region, the lakes of New Hampshire, and thence 



