ii8 



UNIVERSITY OF COLORADO STUDIES 

 TABLE IX— Continued 



X = Printed or specimen record for a Colorado locality. 

 ? =Probable distribution in Colorado. See discussion of species so marked. 



with the altitude of the stream. In considering the distribution 

 within the state, native species are of much more importance than 

 introduced forms. The presence of an introduced fish at a given 

 station speaks only of the ability of that fish to survive in a new 

 environment, since the obstacles which have prevented its reaching 

 the particular locality have been removed by man. The native fish, 

 on the other hand, have reached the particular station presumably 

 as a result of their ability both to overcome the obstacles and to 

 endure the present environment. 



The Rio Grande has fewer native fishes than any of the drainages 

 in Colorado. Five native species are known from the Colorado por- 

 tion of this system at present. One of these, Rhinichthys cataractae 

 dulcis, the Dulcis Minnow, is found on both sides of the Continental 

 Divide and is a fish of wide distribution west of the Mississippi River. 

 No specimens of this Dace have been taken from the Colorado River 

 drainage in Colorado, although it is known from as far west as Cor- 

 vallis, Oregon. Three of the five native species are peculiar to the 

 Rio Grande, occurring only in that system; they are the Rio Grande 

 Trout, Salmo clarkii spilurus, the Rio Grande Sucker, Pantosteus 

 plebius, and the "Pescadito," Richardsonius pulchellus. These fishes 

 are western types and their nearest relatives occur in the Colorado 



