The scientific name of this familiar species was Salmo gairdneri Richardson for well over a century. The change from Salmo to Oncorhynchus was mandated when it was learned that the rainbow trout was more closely related to the Pacific salmon (genus Oncorhynchus) than to the Atlantic salmon and brown trout (genus Salmo). At about the same time, it became obvious that the North American rainbow trout and the Siberian species of similar appearance represented a single species. Walbaum's name mykiss (from Siberia) is older by nearly 40 years than Richardson's Salmo gairdneri, and rules of nomenclature demand acceptance of the older name. The rainbow trout was originally native in coastal streams of the Northwest, but has been widely introduced into other habitats worldwide. It is green dorsally, white or yellowish ventrally, and with a pink to red lateral stripe. It has black spots dorsally on its head, back, and upper sides and on its dorsal, adipose, and caudal fins. Rainbow trout compete with native brook trout in the Park and may be responsible, in part, for their decline (see Salvelinus fontinalis).

Species Characteristics:
Size: specimens larger than 30-35 cm total length (12-14 in.) are unusual in small and medium streams; Tennessee record 6.6 kg (14.5 lb.) from the tailwater of Dale Hollow Reservoir; world angling record 19.1 kg (42 lb. 12 oz.) from Alaska Color: green dorsally, white or yellowish ventrally, with a pink to red lateral stripe; black spots dorsally on head, back, and upper sides, Fins: black spots on dorsal, caudal, and adipose fins Lateral-line scales: 100-150 Gill rakers: 16-22

Similar species: Adults of the three species of trout found in the Park are easily distinguished from one another by dorsal coloration and presence or absence of dark spots on the caudal fin (see brook trout Salvelinus fontinalis and brown trout, Salmo trutta).

Oncorhynchus mykiss is typically a spring spawner with females averaging 2,500-4,500 eggs per year. Young rainbows begin feeding on immature and emergent aquatic insects 16-20 days after hatching. They continue to feed on insects into adulthood as well as feeding on small fish and crustaceans. Rainbows stocked in streams seldom reach sizes close to maximum for the species, and specimens larger than 30-35 cm in total length (12-14 in.) are unusual in small and medium streams. Such small size may be related to strong migratory tendencies of mature fish and physical size of their environment. There is apparently considerable mortality among older stream fish. Growth of individuals in the Park appears to nearly stop during summer months when stream flows are lowest and temperatures highest (S. Moore, pers. comm., Fishery Biologist, Great Smoky Mountains National Park, April 2, 2001).

Originally native to western North America and Siberia, primarily in coastal streams. It has been introduced worldwide in suitable and unsuitable habitats. In Tennessee, it is stocked extensively by state and federal agencies in many streams and reservoirs along the Blue Ridge and in a few cooler creeks, tailwaters, and reservoirs of the Highland Rim and Cumberland Plateau.

The rainbow trout was first introduced into the Smoky Mountains around 1910, and is now common in all streams of the Park to elevations of about 4000 ft (Simbeck 1990). It is considered the prominent game fish of the Park.

Oncorhynchus mykiss has no special status in the Park. However, a valid Tennessee or North Carolina fishing license must be obtained before fishing rainbow trout in the Park

References:

Etnier, David A. and Wayne C. Starnes. 1993. The Fishes of Tennessee. University of Tennessee Press. Knoxville, Tennessee.

Simbeck, Damien J. 1990. Distribution of the Fishes of the Great Smoky Mountains National Park. Master of Science Thesis, University of Tennessee.