FISHES OF COLORADO 8 1 



small worms and crustaceans than other trout. Juday,' however, in the examina- 

 tion of the stomach contents of io6 specimens of this species taken at Twin Lakes 

 found young suckers to form a very considerable item in the food taken. 



The Rainbow Trout in Colorado spawns in the late spring and early summer, 

 from May to July, depending upon the altitude; the higher the station the later 

 the spawning time. The young fish are quite active and grow very rapidly. 

 Jordan and Evermann^ give the following data regarding the relation of size to 

 age under favorable conditions, for this fish: 



1 year M to i ounce 



2 years 8 to lo ounces 



3 years i to 2 pounds 



4 years 2 to 3 pounds 



They add that this species continues to grow until it is eight to ten years old, the 

 rate of growth decreasing with the age of the fish. 



Many large individuals have been taken in Colorado since the introduction of 

 this species. In the Museum of the University of Colorado there is a specimen 

 of the McCloud River Rainbow 22^ inches in length which was caught in Stapp's 

 Lake, Boulder County, August 22, 191 2, by President James H. Baker. Several 

 records of "Rainbows" caught recently, weighing over 5 pounds, have been 

 received. In favorable conditions, particularly in warmer water than that of the 

 mountain streams of Colorado, this species reaches the weight of 10 pounds 

 or more. 



Salmo rivularis Ayres 



Steelhead Trout, "Salmon Trout" 



Salmo rivularis Ayres, Proc. Cat. Acad. Nat. Sci., p. 43, 1855 (Martinez, California). This is 

 the Salmo gairdneri of many writers. 



The Steelhead Trout is a large migratory species native in the Pacific Coast 

 region, ranging north into Alaska. Along the coast it spends a considerable part 

 of its life in the ocean and runs upstream to the headwaters of the Columbia, 

 Snake and other coastwise rivers to spawn. The sea-going individuals become 

 quite large, reaching a weight of 20 pounds or more, but those permanently 

 landlocked do not grow so large. WTierever found this trout is a voracious species. 



Several plantings of Steelheads have been made in Colorado, by both federal 

 and state fish commissions, 14,000 being placed in St. Vrain Creek near Lyons in 

 1902. No reports of recent catches of this species have been received. 



Salmo clarkii Richardson 

 Columbia River Trout 



Salmo clarkii Richardson, Fauna Boreal. Amer., Vol. Ill, p. 225, 1836 (Cathlapootl River). 



This species and its subspecies are known collectively as the Cutthroat Trout 

 because of the red mark on each side of the throat near the inner margin of the 



' JOTAY, Bull. U.S. Fish Com., Vol. XXVI, p. 166, 1906. 

 'Amer. Food and Game Fishes, p. 199, 1902, New York. 



