Chapter 7 

 LIVING FISHES* 



The distribution of living fishes in Colorado bears witness 

 to the permanence of the essential features of the topography in 

 recent geological times. The western drainage, of the Colorado 

 and Gila Rivers, contains a fauna fundamentally different from 

 that of the eastern slope. In the eastern part of the State, up 

 to the foothills and sometimes a short distance into the moun- 

 tains, we find the characteristic species of the western plains 

 region, coming up from Kansas and Nebraska. Several are 

 generally common in the Eastern States. Thus Notropis, a very 

 characteristic genus of so-called minnows, has seven reported 

 species from the Platte basin, two of these also in the Arkansas 

 basin, but none in the Rio Grande basin in Colorado, and none 

 whatever on the western slope. They may yet be found in the 

 Rio Grande Valley, as three species occur in that basin in New 

 Mexico. On the western slope they do not exist, and apparently 

 never have existed. An exception to the general rule is found in 

 the Long-nosed Dace (Rhinichthys cataractae dulcis**), which occurs 

 in Colorado in the Platte, Arkansas and Rio Grande basins, and 

 has also been found west of us in the Great Basin. How this fish 

 came to be so widely distributed is not explained, but certainly 

 it found some way of getting across the divide. Ellis made a 

 careful study of the variations in series from Creede in the Rio 

 Grande basin and Boulder in the Platte basin. There is evidently 

 an incipient differentiation, the Creede specimens having on the 

 average more scales in the lateral line. It is noteworthy that 

 Rhinichthys ascends to higher altitudes than most Cyprinidae, 

 having been taken in Twin Lakes. In the case of the native 

 trout, which ascend to considerable altitudes, the fishes of the 

 Colorado River, Rio Grande and Arkansas-Platte drainages are 

 so closely related that they can all be considered races of a single 

 species. Nevertheless, they are appreciably different, and have 

 distinctive subspecific names, provided by Cope. Unfortunately 

 they have now been mixed up as the result of human introductions. 



*See Max M. Ellis, Fishes of Colorado, Univ. of Colorado Studies, March 1914, for 

 full details. 



**Dr. C. L. Hubbs prefers to call this fish simply R. cataractae, the race dulcis having 

 no sufficient distinctive characters. 



118 



