128 UNIVERSITY OF COLORADO STUDIES 



they are now very scarce. Through the efforts of the state and federal 

 fish commissions many of the better trout streams are quite well 

 restocked and others will doubtless be restocked in the future. The 

 -changes resulting from the use of water for irrigation cannot be helped, 

 as the use of the water for this purpose is undoubtedly just. The 

 useless destruction of fishes attendant upon the deflection of water in 

 unscreened ditches, however, can be, and to a large measure in recent 

 years has been, avoided by the proper screening of the main ditches 

 at the point of withdrawal. 



The introduction of mine and mill waste has been very destructive 

 to the fishes of the state. In 1907 all of the fishes in several miles of 

 Boulder Creek, near Boulder, were killed in this way. So complete 

 was the destruction that for several days the stream carried large 

 numbers of floating fish. Fortunately collections had been made 

 from this creek in 1903 by Juday, and a comparison of the fish fauna 

 as now re-established with that existing in 1903 is possible. The 

 most apparent changes in the fauna are shown in the accompanying 

 table (XIII). 



TABLE XIII 



Comparison of Fish Fauna of Boulder Creek in igo3 and 1912 



Specimens Specimens 



Taken in igo3 Taken in 1Q12 



Couesius dissimilis Numerous None 



Semotilus atromaculatus Few Numerous 



Hyhopsis kentuckiensis Several None 



Rtchardsonius evermanni Three None 



Notropis cayuga Several None 



Catoslomus commersonii sucklii Several Numerous 



griseus Numerous Several 



Etheosloma iowae Several None 



Two species have apparently become more abundant, while others 

 have been completely exterminated or are not yet re-established, 

 judging from existing data (for number of specimens see the specimen 

 lists for the several species). The larger streams have also suffered 

 from the introduction of mill and mine waste. The writer has been 

 told by several of the older fishermen of the abundance of Gizzard 

 Shad, Dorosoma cepedianum (LeSueur),' as far west as Pueblo in the 



« A species of the Dorosomidae. No specimens of this fish taken in Colorado have been examined in this 

 study, and there are no printed records of its occurrence in the state. It has been taken, however, in the 

 Arkansas at Wichita, Kansas, by Jordan {Bull. U.S. Fish Com., Vol. IX, p. 18, 1889), and may occur in the 

 Arkansas in eastern Colorado. If found, it may be recognized by its compressed body, serrate ventral surface, 

 peculiar dorsal fin of 12 rays, the posterior margin of the dorsal and its last ray being greatly elongated. 



