Oncorhynchus mykiss
Physical Description
The elongated, streamlined body of the rainbow trout is typical of all trout, although shape and coloration vary widely depending on habitat, age, and sex. The body shape may also range from slender to thick depending on diet. Coloring may be blue-green to olive with a distinctive reddish pink band along each side, which will vary in brightness. The lower sides are usually silver, fading to white at the belly.
Small black spots are present above and along the lateral line, as well as on the upper fins and tail. On some rainbows, these black spots may cover the entire lower side. Rainbow trout are distinguished from salmon and other trout species by the 8 to 12 rays in the anal fin, a mouth that does not extend past the eye, and no teeth at the base of the tongue.
Coloration varies with size, habitat and season. Stream-dwelling rainbows usually have darker, more brilliant coloring than those found in other waters. River or stream rainbows also possess a brighter pink stripe and more prominent spots, followed by rainbows from lake and lake-stream systems. Conversely, rainbows that migrate to the ocean or Great Lakes (steelhead) will take on a more silver appearance and may not have a pink stripe along the middle of its sides.
In many cases, a rainbow’s coloring also depends on whether the fish was raised in a hatchery or born naturally in a lake, river or stream. Hatchery fish, in general, will not display the brilliant color markings found on “wild” fish. However, if a stocked fish survives for several years in a body of water, it will often display stronger colors.
Range
Rainbow trout are native only to the West Coast of North America, spanning from southern Alaska to northern Mexico, and inland as far as Alberta, Canada, Idaho and Nevada. Due to extensive stocking, the range of the rainbow trout has been extended across the lower Canadian provinces, throughout the Great Lakes region and northeastern United States, all the way to the Atlantic Coast and south through the Appalachians to northern Georgia and Alabama. Rainbows have also been introduced throughout the western United States, as well as selected waters in the Midwest and South.
Rainbow trout have also been introduced to colder waters in New Zealand, Australia, South America, Africa, Japan, southern Asia, Europe, and Hawaii. In these areas, stocking has only been successful at elevations of 4,000 feet or more.
Habitat
Rainbow trout prefer cold-water streams with gravel or rocky bottoms, deep pools, and natural cover. They also thrive in large lakes with cool, deep waters. Though the temperature tolerance of rainbow trout is from 32 F to over 70 F, their ideal temperature range is between 55 and 60 F. They are found in fast moving water, often at the head of rapids or strong riffles, under vegetation and around rocks, fallen trees, or other structures.
Stocked rainbow trout can adapt well to virtually any waters in its preferred temperature range, but they need proper habitat, year-round ideal temperatures, and food sources for long-term survival.
Spawning Habits
Most rainbow trout spawn during the spring, although some varieties spawn at other times. Spawning usually occurs in small tributaries of rivers, or in inlets or outlets of lakes. If possible, rainbow trout usually return to the streams where they hatched. During late winter or early spring, as water temperatures rise, mature rainbows will seek out shallow gravel riffles in a stream or, if they inhabit lakes, a clear-water stream that enters the lake if available and adequate.
Once in the riffles of the stream, the female uses her tail to prepare a nest (redd), normally 4 to 12 inches deep and 10 to 15 inches wide. During the actual spawning activity, both the male and female will hover over the redd, arching their bodies and depositing eggs and milt simultaneously. Females will deposit between 200 and 8,000 eggs into the redd, which are fertilized by a male, and covered with gravel.
Eggs will hatch anywhere from a few weeks to as much as four months after spawning, depending on water temperature. Fry emerge from the gravel in a week or up to several weeks, and will gather in groups and seek shelter along stream banks and pools, or protected shoreline, feeding on crustaceans, plant material, and aquatic insects and their larvae.
Food Usage/Selection
Rainbow trout are opportunistic feeders. Their diet is highly variable, with some fish seemingly taking nearly any living thing that drifts or swims by, as long as it’s small enough to engulf. In most cases, a given body of water will provide one or two staples of the rainbow’s diet, primarily insects or baitfish.
The bulk of their diet is comprised of mayflies, caddis flies, stoneflies and their larvae, small mollusks and baitfish. Fish eggs are another favorite food, particularly when rainbow trout share a stream with migrating salmon, as well as during their own spawning cycles. In large lakes, big rainbow trout feed mainly on baitfish, such as alewives, sculpins or smelt.
Sporting Qualities
Rainbow trout are one of the most highly prized game fish for anglers throughout their native and introduced ranges. Their widespread availability, acrobatic fighting ability and delectable meat make them one of the most popular freshwater fish.
Instead of heading for cover when hooked, as many other trout will do, rainbows will often immediately leap out of the water, then continue these leaps until they are either landed or manage to break free.
Due to a number of factors – habitat, season, and whether they are stocked or wild – rainbow trout can be extremely easy or quite difficult to catch. Wild trout in a small stream are normally wary of unnatural-looking baits or lures, whereas freshly stocked fish in a pond or community lake may readily strike a wide variety of presentations.
Whether an angler uses fly-casting or spinning equipment depends on angler preference and the natural food of the fish in any given body of water. In a river, where rainbow trout feed mainly upon insects, fly-casting methods are commonly preferred, while on big lakes, where rainbow trout feed on forage fish, trolling and spinning methods often have the most success. (Use of live bait to catch rainbow trout is restricted in some areas, so check with the local state fish and game department.)
Notes
· Steelhead trout are considered by scientists to be biologically identical to rainbow trout. The only difference is that steelhead are anadromous, living part of their lives in the ocean and returning to freshwater streams to spawn.
· Rainbow trout are hardy, adaptable fish that live in a variety of habitats. They are thus popular among hatchery managers and are frequently stocked.
· Ten of the top 15 world-record rainbow trout have been caught in Lake Michigan.
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