TROUT Trout are cold-water gamefish that inhabit streams, lakes and rivers. Anglers target both native populations and hatchery-reared fish that are released by fisheries managers ... Read More View All Trout Tips

 

Rainbow trout possess the well-known streamlined salmonid form, though body shape and coloration vary widely and reflect habitat, age, sex, and degree of maturity. The body shape may range from slender to thick. The back may shade from blue-green to olive. There is a reddish-pink band along each side about the midline that may range from faint to radiant. The lower sides are usually silver, fading to pure white beneath. Small black spots are present over the back above the lateral line, as well as on the upper fins and tail. In some locations, the black spots of adults may extend well below the lateral line and even cover the entire lower side. Rainbow trout are positively identified by the 8 to 12 rays in the anal fin, a mouth that does not extend past the back of the eye, and the lack of teeth at the base of the tongue. River or stream residents normally display the most intense pink stripe coloration and heaviest spotting followed by rainbows from lake and lake-stream systems. Spawning trout are characterized by generally darker coloration.

Distribution

Rainbow trout are native to North America west of the Rockies from Alaska into northwestern Mexico. Introductions have extended the range to include the Great Lakes region, south central Canada and portions of the Great Plains east of the Rockies, and southwestern Mexico.

Since rainbow trout generally do not reproduce in some states (particularly in the South), and are unable to survive through the summer in most areas, the species is primarily used in winter put-and-take fisheries. Some states stock trout the year-round in cold water fisheries, notably in Tennessee, northern Arkansas and elsewhere in the South.

Behavior

During late winter or early spring, when water temperatures are on the rise, the maturing adult rainbows usually seek out the shallow gravel riffles or a suitable clearwater stream. Spawning takes place from late March through early July, depending upon the specific location and the severity of the winter. The female uses her tail to prepare a redd, or nest, 4 to 12 inches deep and 10 to 15 inches in diameter. From 200 to 8,000 eggs are deposited in the redd, fertilized by a male, and covered with gravel.

Hatching normally takes place from a few weeks to as much as four months after spawning, depending upon the water temperature. A few more weeks may be required for the tiny fry to emerge from the gravel. Upon emergence, the small trout assemble in groups and seek shelter along the stream margins or protected lake shore, feeding on crustaceans, plant material, and aquatic insects and their larvae. Rainbow trout rear in similar habitat for the first two or three years then move into the larger water of lakes and streams and turn more to a diet of fish, salmon carcasses, eggs, and even small mammals.

Diet

Insects make up a large portion of the diet, along with crayfish and other crustaceans, some lake dwelling species may become planktonic feeders. Trout of all ages will eat nearly anything they can grab, in contrast with the legendary, selective image people often have of the animal's nutrition habits. They are near the top of the food chain in most freshwater environments. However, they are lower on the rung of other freshwater predators such as pike, muskie, lake trout, and chinook salmon. Rainbows will take fish up to and over 1/3 of their length. However they are not quite as piscivorous or aggressive as the brown trout or lake trout, which is actually a char. The rule of thumb is that rainbows consume more fish and fewer insects as they grow, but insects continue to be a part of the diet in most all populations.

Habitat

Rainbows and steelhead occur in well-oxygenated lakes and streams where the temperature normally doesn't rise above 12°C in summer.