FISHES OF COLORADO 129 



Arkansas River and also of the abundance of several species of fishes 

 in the Cuchara River, in the early days before there were large mills 

 and coal mines along these streams. The removal of water for irriga- 

 tion must be considered in this connection as a factor co-ordinate 

 with the introduction of mill waste, since a little waste material would 

 have a higher concentration in a stream carrying little water. 



The introduction of other species into the state has changed the 

 relative abundance of some of the native species, but as far as is known 

 none has been exterminated in this way. One particular case is 

 deserving of attention in this connection. The Yellow-finned Trout, 

 Salmo clarkii macdonaldi, known only from Twin Lakes and once 

 abundant there, is rapidly becoming scarce. Paralleling the decrease 

 in the number of Yellow Fins is a marked increase in the introduced 

 Mackinaw Trout, Crislivomer namaycush. Both are species of the deep 

 water and it may be that the Yellow Fin is an unsuccessful competitor 

 of the introduced Mackinaw, although there may be some other cause 

 for the reduction of the number of Yellow Fins. 



Economic Speci;es 



Several species found in Colorado, other than the trout, have 

 value as food fishes, although the combination of food fishes and game 

 fishes furnished by the Sahnonids makes them by far the most impor- 

 tant group in the state from an economic standpoint. The ease with 

 which trout may be successfully raised has also contributed to the 

 general popularity of these fishes. The ripe adults may be safely and 

 rapidly stripped and the large non-adhesive eggs fertilized in the field, 

 the tough coats of the individual eggs making their safe shipment to 

 the hatcheries possible. Here they are placed in rectangular trays 

 (see Fig. 42) and kept in the hatching-tanks. The removal of the dead 

 eggs is facilitated by their opacity, which makes them quite conspicu- 

 ous in the black trays among the good eggs. During the year 191 2, 

 11,280,000 young trout were distributed from the Colorado state 

 hatcheries.' 



■ Bien. Report Stale Game Fish Com. jot 1911-12, p. 28. 



