The rainbow trout is one of the most respected and sought after of all game fishes.  Rainbow trout have the typical streamlined salmonid form, although body shape and coloration vary widely. Color of the back varies from blue-green to olive, with a reddish-pink band along each side.  The belly is typically white and small black spots are present over the back, upper fins, and tail.
 
Adult rainbows usually seek out the shallow, gravel riffles in late winter, or early spring to spawn. Female use their tails to prepare redds where they deposit up to 8,000 eggs that are fertilized by a male, and covered with gravel.  Depending on water temperature incubation can take from a few weeks to months.  After hatching the fry assemble in groups and seek shelter along shore lines.
 
Opportunistic feeders, rainbows feed on variety of food items ranging from small insects to crayfish. Stream trout often feed heavily on terrestrial insects. Rocky streams produce a many aquatic invertebrates that are also fed upon. In lakes and streams crustaceans, snails, leeches, small fish, and fish eggs also serve as food.
 
Rainbows are popular with anglers for their willingness to take a large number of baits and lures.  Add that they are easily reared to catchable sizes; rainbows are stocked heavily in many states to offer recreational fishing opportunities for many.
 

Description
Oncorhynchus is Greek meaning "hook snout", and mykiss is the Kamchatkan name for rainbow trout. Rainbow trout have a characteristic salmon-like shape. Dark spots are clearly visible on the tail fin, which is slightly forked. The anal fin has 10-12 rays. The back is usually a dark olive color, shading to silvery white on the underside. The body is heavily speckled, and there is a pink to red stripe running lengthwise along the fish's sides.

Life History
Rainbow trout is an anadromous, cool- to cold-water fish species. Although rainbows have been known to tolerate higher temperatures, they do best in areas where the water remains below 70°F. Eggs are laid in shallow nests dug out by the female in gravel riffles. The eggs require continuous oxygenation. At temperatures of about 55°F, the eggs will hatch approximately 21 days after they are laid. Rainbow trout are carnivores, but not exclusively piscivorous. They feed on a wide variety of prey including insects, crustaceans, mollusks and fish. Rainbows with access to the sea have been known to exceed 42 pounds. The record size for those confined to freshwater is 31.27 pounds.

Distribution
 In Texas, high temperatures prevent reproduction or even over-summer survival in most areas, though some may survive in tailrace areas below large dams such as at Canyon Reservoir. The only self-sustaining population in the state exists in McKittrick Canyon in the Guadalupe Mountains.

Other
Since rainbow trout generally do not reproduce in Texas, and are unable to survive through the summer in most areas, the species is primarily used in winter put-and-take fisheries. Each winter, several hundred thousand rainbows are stocked in community fishing lakes around the state. Much enthusiasm is generated by the annual stockings. On occasion, banks are lined with anglers eager to catch their limit immediately after trout are stocked. The state record is 8.24 pounds and was taken from the Canyon Reservoir tailrace.

Courtesy of Texas Parks and Wildlife