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Rainbow Trout – Oncorhynchus mykiss, facts

Rainbow Trout


Members of the salmon family, Rainbow Trout, Oncorhynchus mykiss, are an anadromous species, migrating up-river to spawn. They are native to cool, fresh water, thriving in habitats that do not exceed 70F. Their preference in habitat makes them indicative of clean, clear waters. Rainbow Trout are one of the most popular sporting fish and as a result, are commonly bred and introduced into non-native regions. Alternate names, associated with this species, include Redband Trout, Coastal Rainbow and Steelheads.


With an average lifespan in the wild of 4 to 6 years, Rainbow Trout may grow to an adult size of 20” to 30” and reach an average weight of 2 to 8 lbs. However, some Rainbow Trout have been known to grow as large as 48” and weigh up to 30 lbs. in freshwater and 40 lbs. or greater in saltwater1. The body of the Rainbow Trout, like the common Salmon, is torpedo shaped, featuring a squared, forked tail with 10 to 12 anal rays, and an adipose fin. Differences in geographic habitation can result in variations in coloration and increased concentrations in anal rays. Other physical variations may be brought on by season, such as the hooked jaw, or kype, seen on male fish during the spawning season2.
Coloration is determined by geography, age and reproductive activity. Typically, Rainbow Trout display a predominantly blue-green or yellow-green coloring, providing camouflage against river and lakebeds. However, Rainbow Trout may turn silver while they spend time in salt water. Distinguishing features include red/pink markings running lengthwise on the sides, a silvery-white underside, white mouth and gums, and black speckling across the fins and back.


Rainbow Trout are native to North America, found in waters west of the Rockies, spanning north to Alaska and south to Mexico. Geographic populations are commonly identified by distinct names. The term Redband typically refers to Rainbow Trout living east of the Cascade Mountains in the U.S. and in the Upper Fraser River of British Columbia. Steelheads are Rainbow Trout that migrate to the Pacific as juveniles, spending time in saltwater before returning to freshwater to spawn3.

Due to their popularity as a sport fish and their ability to thrive in hatcheries, the Rainbow trout has been introduced to streams, rivers and lakes one every continent except for Antarctica, gaining this species distinction as invasive in certain locations. In the United States, there are introduced populations in 47 states, extending from the Great Lakes region, to south central Canada to the Great Plains east of the Rockies, and southwestern Mexico4.


Rainbow Trout live in fresh, cool waters and require a temperature not exceeding 70 for survival. These freshwater bodies include headwaters, creeks, rivers, lakes, estuaries, and oceans. Preferred habitats are complex, including features that provide protection, feeding opportunities and habitat stabilization for the trout. This diverse ecosystem is comprised of submerged boulders and wood, overhanging vegetation, root masses, and beds of aquatic plants and clean gravel, interspersed between turbulent runs, slow-flowing pools, and deep water. Because trout are solitary in nature, these features also create barriers between habitats, allowing Rainbow Trout to establish territories within close proximity of other populations.

Adult Steelheads (‘sea-run rainbow trout,’) have been known to follow fresh water routes to the Pacific, spending up to several years in an oceanic habitat before returning to fresh water to spawn.

A large percentage of native Rainbow Trout habitats have been compromised or lost due to many factors, including soil erosion, loss of riparian vegetation (that found growing along banks,) logging, mining, pollution due to agricultural and municipal development, and dam and road construction. In addition to loss of habitats, these factors also damage migratory routes, hindering upstream migration during the spawning season. These factors have lead to a reduction of native Rainbow Trout populations, forcing nine populations of Steelheads to the federal endangered species list.


Rainbow trout are opportunistic and migratory feeders5. Their carnivorous diets consist of aquatic and terrestrial items, including Insects, crustaceans, small fish, plankton, leeches, mollusks, and fish eggs. When food supplies are limited, Rainbow Trout have been known to travel long distances in search of new sources.


Rainbow Trout typically spawn in the spring and early summer, seeking out stream riffles downstream from pools, lake inlet or outlet streams or main river channels and tributaries. During the spawning season Steelhead trout have been known to migrate from the ocean to the freshwater where they hatched, identifying them as an anadromous or migratory species. Female Rainbow Trout seek out moving water over clean, sediment-free gravel, ranging from ½” to 3” in diameter, to build their nests. The female will use her tail to dig a shallow pit, called a redd, depositing a portion of her eggs to be fertilized by a male. After the first nest has been fertilized and covered with gravel, the female will dig another redd upstream, varying the water depth and velocity of the location to increase the survival rate of the eggs. After fertilization, the eggs require consistent temperatures of around 55F and continuous oxygenation through the clean gravel and hatch within 21 days6. Young trout will remain in the gravel from which they hatched until yolk reserves are depleted, emerging to search for new food sources7.

Rainbow Trout that have been introduced to non-native environments have a diminished rate of reproduction due to improper temperatures, and spawning environments. Because of this, states, including Ohio and Texas, must continually restock trout in their freshwaters to provide fisherman with this species. The Ohio Division of Wildlife introduces young trout into Lake Erie tributaries, where they will live for 1 to 2 years before migrating to the lake. The adult trout will live in the lake for up to several years, if allusive to fisherman, before returning to the tributaries and heading upstream to attempt to spawn8.

Rainbow Trout Fishing: The Rainbow Trout’s history with fisherman has made it one of “the top five sport fishes in North America, and it is considered by many to be the most important game fish west of the Rocky Mountains” 9.

“To catch a rainbow trout, an angler needs to be aware of the fish’s behavior in different water conditions. In streams, rainbow trout tend to select areas with gravel or rocky bottom that have cover such as boulders, logs or deep water nearby. In ponds and lakes, rainbow trout tend to swim around looking for food, especially near cover such as a weed line.

A variety if techniques can be used to catch rainbow trout: bait, artificials and fly fishing. When bait fishing, size 6-10 baitholder hooks and 4-8 lb. test line are best to use to suspend the bait in the water or split shot can be used to keep the bait on the bottom. Baits commonly used are worms, minnows, corn, crickets, salmon eggs or commercially produced baits such as Berkley Power Bait.

Fishing with artificials is a technique that uses a non-food item to imitate a food item. Spinner and spoons 1/32-1/8 oz. are commonly used for trout. They are made of metal and imitate a baitfish. Artificials can either be cast out and retrieved or trolled. A piece of bait can be added to an artificial to enhance its attractiveness” 10.

Notes of Interest:

Symbol of: Washington State

The largest rainbow trout on record weighed 57 lbs (25.8 kg) and was estimated to be 11 years old11.


1. http://www.tpwd.state.tx.us/huntwild/wild/species/rbt/
2. www.dnr.state.oh.us/LinkClick.aspx?link=6733&tabid=6518
3. http://www.fws.gov/northeast/wssnfh/pdfs/RAINBOW1.pdf
4. http://www.tpwd.state.tx.us/huntwild/wild/species/rbt/
5. http://www.fws.gov/northeast/wssnfh/pdfs/RAINBOW1.pdf
6. http://www.tpwd.state.tx.us/huntwild/wild/species/rbt/
7. www.dnr.state.oh.us/LinkClick.aspx?link=6733&tabid=6518
8. www.dnr.state.oh.us/LinkClick.aspx?link=6733&tabid=6518
9. http://www.fws.gov/northeast/wssnfh/pdfs/RAINBOW1.pdf
10. http://www.dec.ny.gov/docs/regions_pdf/rainbowtrout3.pdf
11. http://animals.nationalgeographic.com/animals/fish/rainbow-trout/

“Rainbow Trout.” National Geographic. National Geographic Society, 1996-2013. Web. 26 Feb. 2013.

“Rainbow Trout (Oncorhynchus mykiss).” U.S. Fish and Wildlife Service. Version 13. United States Department of Agrictulture: Natural Resources Conservation Service, May 2000. Web. 26 Feb. 2013.

“Rainbow Trout.” ODNR Division of Wildlife. Ohio Department of Natural Resources. Web. 26 Feb. 2013.

“Rainbow Trout (Oncorhynchus mykiss).” Texas Parks and Wildlife. Texas Parks and Wildlife Department. Web. 26 Feb. 2013.


“Fishing for Rainbow Trout.” New York Department of Environmental Conservation. Web. 26 Feb 2013.
Current distribution of Rainbow Trout, including native habitats and domesticate populations. Photo Courtesy of http://www.fws.gov/northeast/wssnfh/pdfs/RAINBOW1.pdf

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