ii6 



UNIVERSITY OF COLORADO STUDIES 



between the trout and the suckers; the suckers eat trout eggs but in turn large 

 numbers of young suckers are eaten by the trout. 



Colorado specimens. — University Museum: Big Beaver Creek, Rio Blanca County, July g, 

 1907 (90 mm.), E. R. Warren and J. W. Frye, No. 410; Lightner's Creek, Durango, August 10, 

 1912 (11 specimens, 20-30 mm.), M. M. Ellis, No. 411; Rio Florida, near Durango, August 11, 

 1912 (8 specimens, 55-140 mm.), J. Henderson and M. M. Ellis, No. 412; Colorado College Museum: 

 Grand River near McCoy, Eagle County, Grand River 12 miles above Glenwood Springs, San Juan 

 River, Pagosa Springs, E. R. Warren; Stale Teachers' College Museum: Pueblo and Durango, 

 A. E. Beardsley. 



TABLE Vni 

 SuMitAEY OF Species Known at Present from Coiorado 



Distribution of Fishes in Colorado 

 Relations to River Systems 

 Within the state the distribution of the fishes of Colorado is best 

 shown by a comparison of the fauna of the four drainages and of the 

 altitudinal zones. Barring the introduction of species by man, natural 

 barriers as mountain ranges and arid areas are quite effective against 

 the migration of fishes, so that in general the more isolated two river 

 systems are the more diverse their fish fauna. Two of the four 

 drainages of Colorado are entirely independent, the Rio Grande and 

 the Colorado River. The Platte and the Arkansas form a third unit 

 independent of the first two. Thus there are three different fish 

 faunas represented, correlated with these three drainage units. As 

 the mountains are approached there are abrupt changes in the nature 

 of the streams and the temperature of their waters, rendering them 

 unsuitable for certain fishes and making possible the presence of 

 others. In this way there is an intra-drainage distribution correlated 



