FISHES OF COLORADO 75 



ray of the dorsal; anal fin almost as large as the dorsal, of 11 to 13 rays; adipose 

 fin large and prominent, its tip reaching beyond the level of the last anal ray; 

 caudal peduncle narrow, its least depth about 3 in the head; caudal fin deeply 

 forked; scales not very small, 8 to 10, 80-90, 8 to 10, those on the sides of the body 

 of breeding males with tubercles. 



Color above dark grayish or greenish blue shading into silvery on the sides 

 and grayish white below; dorsal fin dark, adipose and caudal grayish blue to 

 steel-blue, pectoral, ventral and anal fins dusky, outer portion of all fins margined 

 with black; young with dusky parr marks. Size moderate, reaching a length of 

 12 inches or more and a weight of 5 pounds, average specimens about a pound. 



Williamson's Whitefish is a species of the western slope of the Rocky Moun- 

 tains, ranging from Colorado northwestward through Utah and Idaho to the 

 Pacific Coast and British Columbia. A variety, C williamsoni cismontanus 

 Jordan, is known from the tributaries of the Upper Missouri east of the Continental 

 Divide. In cold deep lakes the Whitefish finds its favorite habitat, running into 

 small streams during the spawning season, the late fall and early winter.' As a 

 game fish this species is much like the trout, taking both the fly and still bait. Its 

 flesh is excellent. In Colorado this fish is found in the Yampa and White River 

 drainages and has been reported to the writer as quite abundant in several local- 

 ities. It is known locally as the "Grayling," which it resembles superficially, 

 but from which it may be easily separated by the small dorsal fin and the absence 

 of several rows of bright orange spots on the dorsal fin and the three pink stripes 

 on the ventrals, these markings being characteristic of the true Grayling, Thymallus 

 montanus. The Whitefish is also known as the "Rocky Mountain Herring." 



Subfamily Salmoninae 

 Genus SALMO (Artedi) Linnaeus 

 The Salmon and Trout 



Salmo Artedi, Genera Piscium, 1738. 



Salmo Linnaeus, Syslema Naturae, ed. X, p. 308, 1758. 



Body moderately elongate and compressed; mouth large, its angle reaching 

 to or beyond the level of the center of the eye; lower jaw equal to or barely 

 exceeding the upper, lower jaw of breeding males often upturned at the tip; teeth 

 on the tongue, palatine bones, vomer and both jaws; vomer flat; pyloric coeca 

 numerous; scales small. 



Since the species of this genus, particularly the trout, are so closely related, the 

 variation in the measurements usually given is less in some cases between different 

 species of Salmonids than that between individuals of species of some other groups. 

 Accordingly the technical descriptions of the Salmonids found in Colorado are 

 omitted and the general description given under this head. 



' EvERMANN AND Smith, Rept. U.S. Com. Fisheries, p. 293, 1896. 



