Oncorhynchus mykiss is among the most important game fishes in North America. These common fish are found in cold headwaters, creeks, and small to large rivers, as well as lakes. They are anadromous in coastal streams, moving upstream from the ocean to spawn (unlike salmon, adults usually survive spawning and may breed again). (Page and Burr 1991)

The different forms of Oncorhynchus mykiss are known by different common names. The sea-run Rainbow Trout are known as Steelhead; interior populations are sometimes known as Redband Trout. These fish are highly variable in color, but have small, irregular black spots on the back and most fins. There are radiating rows of black spots on the caudal (tail) fin and a pink to red stripe on the side. Stream and spawning fish have intense dark colors whereas lake fish are light and silvery. The upper jaw reaches barely behind the eye in young and female individuals, but well behind the eye in large males. Sea-run individuals (Steelhead) are silvery and largely lack the pink stripe on the side; they typically develop a more pointed head and grow much larger than Rainbow Trout. (Page and Burr 1991)

Rainbow Trout are native to the Pacific Slope of North America from Alaska and northwestern Canada to Baja California. They have been widely introduced in cold waters elsewhere in North America and the rest of the world. (Page and Burr 1991)

In contrast to the Rainbow Trout, the Golden Trout (O. aguabonita) has a red belly and cheek, a gold lower side, and large black spots on the dorsal and caudal fins (but in some areas where they co-occur, these two species hybridize). The Cutthroat Trout (O. clarki) has an orange or red "cutthroat" mark on the underside of the lower jaw and small teeth on the floor of the mouth between the gill arches (no such teeth are present in Rainbow Trout). Salvelinus species have light spots on a dark background. Salmon have 13 or more anal rays (8 to 12 in Rainbow Trout). (Page and Burr 1991)

For detailed information on the biology and status of this species, including conservation issues, see this resource from the NOAA Fisheries Office of Protected Resources.

Inhabits cold headwaters, creeks, small to large rivers, and lakes. Anadromous in coastal streams (Ref. 5723). Stocked in almost all water bodies as lakes, rivers and streams, usually not stocked in water reaching summer temperatures above 25°C or ponds with very low oxygen concentrations. Feeds on a variety of aquatic and terrestrial invertebrates and small fishes. At the sea, preys on fish and cephalopods. Undertakes short spawning migrations. Anadromous and lake forms may migrate long distances to spawning streams (Ref. 59043). Utilized fresh, smoked, canned, and frozen; eaten steamed, fried, broiled, boiled, microwaved and baked (Ref. 9988). Cultured in many countries and is often hatched and stocked into rivers and lakes especially to attract recreational fishers (Ref. 9988).

Arctic Ocean, Atlantic Europe, Baltic sea, British Columbia, Canadian Exclusive Economic Zone [Pacific part], Coastal Waters of Southeast Alaska and British Columbia, Eritrea, European waters (ERMS scope), FAO fishing area 67, Gulf of Maine, Kenya, Madagascar, Mauritius, New Zealand Exclusive Economic Zone, North East Pacific, North Pacific, North Sea, North West Atlantic, North West Territories, Oosterschelde, Polish Exclusive Economic Zone, Red Sea, Reunion, South Africa (country), Tanzania, United Kingdom Exclusive Economic Zone

Oncorhynchus_mykiss are only native to the Pacific Coast of North America, extending from Alaska down to the border between California and Mexico. However, they have been introduced throughout the United States. and in every continent except for Antarctica for game fishing purposes. There are two forms: freshwater resident and anadromous. The resident form is commonly called rainbow trout while the anadromous form is called steelhead.

Biogeographic Regions: nearctic (Introduced , Native ); palearctic (Introduced ); oriental (Introduced ); ethiopian (Introduced ); neotropical (Introduced ); australian (Introduced )

Other Geographic Terms: cosmopolitan

Native to Pacific Slope from Kuskokwim River, Alaska to (at least) Rio Santa Domingo, Baja California, Mexico; upper Mackenzie River drainage (Arctic basin), Alberta and British Columbia in Canada; endorheic basins of southern Oregon, USA. Widely introduced in cold waters elsewhere in North America and rest of the world (Ref. 5723). Eastern Pacific: Kamchatkan Peninsula and have been recorded from the Commander Islands east of Kamchatka and sporadically in the Sea of Okhotsk as far south as the mouth of the Amur River along the mainland. The records outside Kamchatka probably represent migrating or straying Kamchatkan steelhead (penshinensis) rather than the established native population (Reg. 50080). Several countries report adverse ecological impact after introduction.

Oncorhynchus mykiss are only native to the Pacific Coast of North America, extending from Alaska down to the border between California and Mexico. However, they have been introduced throughout the United States. and in every continent except for Antarctica for game fishing purposes. There are two forms: freshwater resident and anadromous. The resident form is commonly called rainbow trout while the anadromous form is called steelhead.

Biogeographic Regions: nearctic (Introduced , Native ); palearctic (Introduced ); oriental (Introduced ); ethiopian (Introduced ); neotropical (Introduced ); australian (Introduced )

Other Geographic Terms: cosmopolitan

Native to the Pacific coastal inland waters. Introduced into the Atlantic drainages.

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Native to streams along the Pacific coast of North America from the Kuskokwim River, Alaska, south to northern Baja California; also the upper Mackenzie River drainage (Arctic basin), Alberta and British Columbia, and endorheic (i.e. having no outflow of water) basins of southern Oregon (Page and Burr 1991). The species has been widely introduced and established in suitable habitats all over the world (Lee et al. 1980). At sea, O. mykiss occurs hroughout the North Pacific above 40° N from the North American coast to the Sea of Okhotsk (Burgner et al. 1992); it is most abundant in the Gulf of Alaska and eastern part of the North Pacific, conforming to the 5°C isotherm in the north and 15°C isotherm in the south. Seasonal shifts in distribution are correlated with changes in water temperature (Sutherland 1973).

Historic Range:
North Pacific Ocean from the Kamchatka Peninsula in Asia to the northern Baja Peninsula

North Pacific and adjacent basins, introduced widely elsewhere.

Physical description varies widely with sex, age, and habitat. In general, they are streamlined, with 8 to 12 spines in the anal fin and lack teeth at the base of the tongue (unlike their close relatives, Oncorhynchus_clarkii). The undersides tend to be silvery with a pinkish red stripe along the upper-middle part of the body, though this stripe can vary from dark to light. Resident rainbows and spawning steelhead tend to be lighter with more pronounced pink stripes, while ocean-going steelhead are darker and silvery to blend into their ocean environment. Most have black spots above the lateral line, and resident rainbows tend to have more intense spotting, well below the lateral line. Juvenile fish have 8 to 13 parr marks on their sides and become silvery as they mature.

Range mass: 25.4 (high) kg.

Average mass: 4 kg.

Range length: 120 (high) cm.

Range basal metabolic rate: 0.6 to 75 cm^3 oxygen/hour.

Average basal metabolic rate: 55 cm^3 oxygen/hour.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: male larger

Dorsal spines (total): 0; Dorsal soft rays (total): 10 - 12; Analspines: 0; Analsoft rays: 8 - 12; Vertebrae: 60 - 66

Physical description varies widely with sex, age, and habitat. In general, they are streamlined, with 8 to 12 spines in the anal fin and lack teeth at the base of the tongue (unlike their close relatives, Oncorhynchus clarkii). The undersides tend to be silvery with a pinkish red stripe along the upper-middle part of the body, though this stripe can vary from dark to light. Resident rainbows and spawning steelhead tend to be lighter with more pronounced pink stripes, while ocean-going steelhead are darker and silvery to blend into their ocean environment. Most have black spots above the lateral line, and resident rainbows tend to have more intense spotting, well below the lateral line. Juvenile fish have 8 to 13 parr marks on their sides and become silvery as they mature.

Range mass: 25.4 (high) kg.

Average mass: 4 kg.

Range length: 120 (high) cm.

Range basal metabolic rate: 0.6 to 75 cm^3 oxygen/hour.

Average basal metabolic rate: 55 cm^3 oxygen/hour.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: male larger

Maximum size: 1200 mm TL

120 cm TL (male/unsexed; (Ref. 5504)); max. published weight: 25.4 kg (Ref. 7251); max. reported age: 11 years (Ref. 12193)

Length: 100 cm

Body elongate, somewhat compressed especially in larger fish. No nuptial tubercles but minor changes to head, mouth and color occur especially in spawning males. Coloration varies with habitat, size, and sexual condition. Stream residents and spawners darker, colors more intense. Lake residents lighter, brighter, and more silvery. Caudal fin with 19 rays (Ref. 2196). Differs from Oncorhynchus gorbuscha by having the following unique characters: by having the following unique characters: anal fin with 6-9½ (usually 8½ ) branched rays; 115-130 scales in midlateral row; 16-17 gill rakers; breeding males lacking hump; juveniles lacking parr marks; wide pink to red stripe from head to caudal base, except in sea-run form; and juveniles with 5-10 parr marks (Ref. 59043).

The natural habitat of the species is freshwater with about 12°C in summer. It is unclear whether its anadromy is a truly genetic adaptation or simply an opportunistic behavior. It seems that any stock of rainbow trout is capable of migrating, or at least adapting to seawater, if the need or opportunity arises. Adults feed upon fish eggs, minnow and other small fish (including other trout); young feed on small insects and crustaceans. Utilized fresh, smoked, canned and frozen; eaten steamed, fried, broiled, boiled, microwaved and baked (Ref. 9988). Rainbow trout is cultured in many countries and is often hatched and stocked into rivers and lake especially to attract recreational fishermen (Ref. 9988).

Montana: both pure and moderately hybridized populations of westslope cutthroat trout have a high incidence of basibranchial teeth, whereas pure rainbow trout lack these teeth; presence of basibranchial teeth in some individuals of a rainbow trout population indicates hybridization with westslope cutthroat trout (Leary et al. 1996).

This taxon is one of a number of benthopelagic species in the Amur River system. Benthopelagic river fish are found near the bottom of the water column, feeding on benthos and zooplankton

The persistence of mercury contamination in Amur River bottom sediments is a major issue, arising from historic cinnabar mining in the basin and poor waste management practises, especially in the communist Soviet era, where industrial development was placed ahead of sound conservation practises.

Other large benthopelagic river fish of the Amur Basin is the 200 cm yellowcheek (Elopichthys bambusa) and the 122 cm Mongolian redfin (Chanodichthys mongolicus)

Freshwater, brackish, or marine waters of temperate zones. The anadromous form, called steelhead, spawn and complete their early development in freshwater mountain streams, then migrate to spend their adult life in the ocean. In freshwater, they prefer cool water but have been known to tolerate water temperatures up to 24°C (native climates have water temperatures around 12°C in the summer). Productive streams have a good mixture of riffles and pools and overhanging vegetation for shade. Most importantly, they require gravel beds to lay their eggs, and therefore, are sensitive to sedimentation and channel scouring. Juvenile trout prefer protective cover and low velocity water and have been known to be swept away and killed in water that is too fast. Since they are native to the western U.S., then tend to be found in coastal streams and rivers which naturally have reduced flow in summer months.

Range elevation: 0 to 3000 m.

Range depth: 10 to 200 m.

Habitat Regions: temperate ; tropical ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; lakes and ponds; rivers and streams; temporary pools; coastal ; brackish water

benthopelagic; anadromous (Ref. 51243); freshwater; brackish; marine; depth range 0 - 200 m (Ref. 50550)

Freshwater, brackish, or marine waters of temperate zones. The anadromous form, called steelhead, spawn and complete their early development in freshwater mountain streams, then migrate to spend their adult life in the ocean. In freshwater, they prefer cool water but have been known to tolerate water temperatures up to 24°C (native climates have water temperatures around 12°C in the summer). Productive streams have a good mixture of riffles and pools and overhanging vegetation for shade. Most importantly, they require gravel beds to lay their eggs, and therefore, are sensitive to sedimentation and channel scouring. Juvenile trout prefer protective cover and low velocity water and have been known to be swept away and killed in water that is too fast. Since they are native to the western U.S., then tend to be found in coastal streams and rivers which naturally have reduced flow in summer months.

Range elevation: 0 to 3000 m.

Range depth: 10 to 200 m.

Habitat Regions: temperate ; tropical ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; lakes and ponds; rivers and streams; temporary pools; coastal ; brackish water

nektonic

The natural habitat of the species is fresh water with about 12°C in summer.

Depth range based on 29 specimens in 2 taxa.

Environmental ranges
  Depth range (m): 0.142 - 33

Graphical representation

Depth range (m): 0.142 - 33
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Freshwater

Comments: Capable of surviving in a wide range of temperature conditions. Does best where dissolved oxygen concentration is at least 7 ppm. Anadromous populations occur in coastal rivers. Resident populations now inhabit small headwater streams, large rivers, lakes, or reservoirs; often in cool clear lakes and cool swift streams with silt-free substrate. In streams, deep low velocity pools are important wintering habitats (Sublette et al. 1990).

Usually requires a gravel stream riffle for successful spawning. Lake populations move to tributaries to spawn. Eggs are laid in gravel in a depression made by the female. Salinity of 8 ppt is the upper limit for normal development of eggs and alevins (Morgan et al. 1992).

Anadromous. Fish that ascend rivers to spawn, as salmon and hilsa do. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Anadromous forms migrate up to at least hundreds of miles between spawning streams and nonspawning marine waters. Stream-dwelling trout may spend an entire life in few hundred meters of stream (Moyle 1976). Lake-dwelling trout typically migrate to tributaries to spawn.

Rainbow trout and steelhead are insectivorous and piscivorous. Resident rainbow trout tend to eat more fish than steelhead. Both species primarily feed on invertebrate larvae drifting in mid-water to conserve energy that would be expended if they were foraging for food in the substrate. Young rainbow trout and steelhead eat insect larvae, crustaceans, other aquatic invertebrates, and algae.

Animal Foods: fish; insects; aquatic or marine worms; aquatic crustaceans

Plant Foods: algae

Anadromous (Ref. 5951). Young rainbow trout feed predominantly on zooplankton (Ref. 26523). Rainbow trout of all sizes fed mainly on midge (adults, larvae and pupae). As the fish grew larger, terrestrial prey became the most important food item (Ref. 55755). Possible cohabitation with G. olidus (Ref. 26860). Rainbow trout also have sea dwelling populations known as 'steelhead' (Ref. 6390).

Rainbow trout and steelhead are insectivorous and piscivorous. Resident rainbow trout tend to eat more fish than steelhead. Both species primarily feed on invertebrate larvae drifting in mid-water to conserve energy that would be expended if they were foraging for food in the substrate. Young rainbow trout and steelhead eat insect larvae, crustaceans, other aquatic invertebrates, and algae.

Animal Foods: fish; insects; aquatic or marine worms; aquatic crustaceans

Plant Foods: algae

Primary Diet: carnivore (Insectivore )

Comments: In lakes, feeds mostly on bottom-dwelling invertebrates (e.g., aquatic insects, amphipods, worms, fish eggs, sometimes small fish) and plankton. In streams, feeds primarily on drift organisms. May ingest aquatic vegetation (probably for attached invertebrates). Diet changes seasonally. In the ocean, the diet consists of fishes and crustaceans.

Animal / parasite / endoparasite
metacaria (diplostomula) of Diplostomum spathaceum endoparasitises eye (lens) of Salmo gairdneri

Rainbow trout and steelhead are important predators in their native habitats, they also serve as important sources of food for larger predators.

Commensal/Parasitic Species:

• sea lamprey (Petromyzon_marinus)

In the Great Lakes, sea lampreys are the most common predators of all Salmonidae species, including rainbow trout. Other predators in both native and introduced habitats include: larger Salmonidae, fish-eating birds like great blue herons (Ardea_herodias), mergansers (Mergus), and kingfishers (Ceryle), and mammals including mink (Mustela_vison and Mustela_lutreola), raccoons (Procyon_lotor), river otters (Lontra), grizzly bears (Ursus_arctos), American black bears (Ursus_americanus), humans, and larger marine mammals who feed on migrating steelhead. Rainbow trout tend to stick to the sides of streams and rivers where shading is prevalent, the water is less swift, and protection is greatest. Trout species are vigilant and capable of rapid swimming to escape predation.

Known Predators:

• kingfishers (Ceryle)
• grizzly bears (Ursus_arctos)
• American black bears (Ursus_americanus)
• river otters (Lontra_canadensis)
• mink (Mustela_vison and Mustela_lutreola)
• raccoons (Procyon_lotor)
• sea lampreys (Petromyzon_marinus)
• mergansers (Mergus_merganser)
• great blue herons (Ardea_herodias)
• other trout species (Salmonidae)
• humans (Homo_sapien)

Rainbow trout and steelhead are important predators in their native habitats, they also serve as important sources of food for larger predators.

Commensal/Parasitic Species:

• sea lamprey (Petromyzon marinus)

In the Great Lakes, sea lampreys are the most common predators of all salmonid species, including rainbow trout. Other predators in both native and introduced habitats include: larger trout, fish-eating birds like great blue herons (Ardea herodias), mergansers (Mergus), and kingfishers (Ceryle), and mammals including mink (Neovison vison and Mustela lutreola), raccoons (Procyon lotor), river otters (Lontra), grizzly bears (Ursus arctos), American black bears (Ursus americanus), humans, and larger marine mammals who feed on migrating steelhead. Rainbow trout tend to stick to the sides of streams and rivers where shading is prevalent, the water is less swift, and protection is greatest. Trout species are vigilant and capable of rapid swimming to escape predation.

Known Predators:

• kingfishers (Ceryle)
• grizzly bears (Ursus arctos)
• American black bears (Ursus americanus)
• river otters (Lontra canadensis)
• mink (Neovison vison and Mustela lutreola)
• raccoons (Procyon lotor)
• sea lampreys (Petromyzon marinus)
• mergansers (Mergus merganser)
• great blue herons (Ardea herodias)
• other trout species (Salmonidae)
• humans (Homo sapien)

Whirling Disease 3. Parasitic infestations (protozoa, worms, etc.)

Proliferative Kidney Disease. Parasitic infestations (protozoa, worms, etc.)

Hysterothylacium Infection (Hysterothylacium sp.). Parasitic infestations (protozoa, worms, etc.)

Epitheliocystis. Bacterial diseases

Enteric Redmouth Disease. Bacterial diseases

Camallanus Infection 16. Parasitic infestations (protozoa, worms, etc.)

Aeromonosis. Bacterial diseases

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: This species is represented by a very large number of occurrences (subpopulations).

In a survey of populations in the contiguous U.S., Huntington et al. (1996) identified 28 healthy native stocks of winter steelhead (20 in Washington, 7 in Oregon, 1 in California) and 6 healthy native stocks of summer steelhead, all in Oregon.

>1,000,000 individuals

Comments: Total adult population size for all subspecies and stocks greatly exceeds 1 million.

Total annual abundance for all North American steelhead stocks was estimated at 1.6 million fish (Burgner et al. 1992).

Normal life span 5-6 years (Simpson and Wallace 1982). Predation by Caspian terns and double-crested cormorants causes significant mortality of juvenile steelhead in the Columbia River estuary (Ryan et al. 2003). Aggressively defends feeding territories in streams. Has caused contraction of range of native brook trout in southern Appalachian Mountains region (Larson and Moore 1985).

There is little communication between rainbow trout and steelhead. Once the fry emerge from the gravel, they become hostile to each other and compete for habitat. Larger fish usually win out the best habitat and food sources, and there is a size hierarchy within aquatic systems among all trout species. Potential mates communicate before spawning with visual cues. Oncorhynchus_mykiss individuals are visual predators, relying on a keen sense of vision to detect prey. Salmonidae species use both chemical cues and detection of the earth's magnetic fields to navigate to and from natal streams and on ocean journeys.

Communication Channels: visual ; tactile

Perception Channels: visual ; magnetic

There is little communication between rainbow trout and steelhead. Once the fry emerge from the gravel, they become hostile to each other and compete for habitat. Larger fish usually win out the best habitat and food sources, and there is a size hierarchy within aquatic systems among all trout species. Potential mates communicate before spawning with visual cues. Oncorhynchus mykiss individuals are visual predators, relying on a keen sense of vision to detect prey. Trout species use both chemical cues and detection of the earth's magnetic fields to navigate to and from natal streams and on ocean journeys.

Communication Channels: visual ; tactile

Perception Channels: visual ; magnetic

Comments: May feed at any time throughout a 24-hour period, but usually feeds most actively around dusk.

Oncorhynchus_mykiss larvae go through a series of morphological changes to prepare for life in the sea, and spend their adult life there for 2 to 3 years before migrating upstream to spawn in their natal stream.

Development - Life Cycle: metamorphosis

Reported not to establish breeding populations if the peak emergence of fry corresponds to flood season and cold summer temperatures and if temperature does not fall below 13° C (Ref. 59043). Males mature generally at 2 years and females at 3. Spawning happens from November until May in the Northern hemisphere and from August to November on the Southern hemisphere. The size of the eggs depends on the size of the female. In captivity spawning is fostered by abdominal massage. Egg size 3-6 mm, fry length after hatching 12-20 mm. Hatchlings are well developed and equipped with a large yolk sac. The female finds a spot and digs a pit. While digging, an attendant male courts her or is busy driving away other males. As soon as the pit is completed, the female drops into it and is immediately followed by the male. The pair is side by side, they open their mouth, quiver and release egg and sperm. Females produce from 700 to 4,000 eggs per spawning event (Ref. 4706). At this point, a subordinate male moves in and releases sperm into the nest. The female quickly moves to the upstream edge of the nest and starts digging a new pit, covering the eggs. The whole process is repeated for several days until the female deposits all her eggs (Ref. 27547). Young fish move downstream at night, shortly after emergence (Ref. 4706). Reproductive strategy: synchronous ovarian organization, determinate fecundity (Ref. 51846).

Oncorhynchus mykiss larvae go through a series of morphological changes to prepare for life in the sea, and spend their adult life there for 2 to 3 years before migrating upstream to spawn in their natal stream.

Development - Life Cycle: metamorphosis

Oncorhynchus_mykiss individuals live for 6 to 8 years in the wild, possibly up to 11 years.

Range lifespan

Status: wild: 11 (high) years.

Typical lifespan

Status: wild: 6 to 8 years.

Oncorhynchus mykiss individuals live for 6 to 8 years in the wild, possibly up to 11 years.

Range lifespan

Status: wild: 11 (high) years.

Typical lifespan

Status: wild: 6 to 8 years.

Female fish find suitable nest sites while their male mate guards the site from other interested males and predators. The female digs the nest (called a redd) with her anal fin and then descends upon it to position her vent and anal fin into the deepest part of the redd. The male joins her in a parallel position so that their vents are opposite each other. The male and female open their mouths, arch their backs, and deposit the eggs and milt (fish sperm) at the same time. The eggs are enveloped in a cloud of milt and are fertilized. Only a few seconds elapse from the time the female drops into the redd and fertilization occurs. The female then covers the nest with gravel and repeats the process again a few times until she has deposited all of her eggs.

Mating System: polygynous

Adult rainbow trout and steelhead lay their eggs in a series of nests in gravel. Collectively, the nests are called a redd. When they hatch, the hatchlings are still attached to, and survive on their yok sac. They remain in the protective gravel for about 2 to 3 weeks when they have shed their yolk sacs and are fit enough to survive in the open water. Juvenile fish tend to stick to shallow and side areas of the streams where there is protective cover and slow-moving currents. The remain in their native streams for 1 to 3 years while they grow fit enough to spawn or migrate to the ocean, in the case of steelheads.

Breeding interval: Rainbow trout breed every three to five years. Though steelhead are one of the only salmonids able to spawn twice in a lifetime, the return rate is very low, about 10-20%

Breeding season: Spawning occurs from March to July, depending on temperature and other climatic variables. Winter steelhead in California start spawning as early as January.

Range number of offspring: 200 to 8000.

Range time to hatching: 3 to 16 weeks.

Range time to independence: one to three years.

Range age at sexual or reproductive maturity (female): 3 to 11 years.

Range age at sexual or reproductive maturity (male): 3 to 11 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization (External ); oviparous

Average number of offspring: 3500.

Female rainbow trout and steelehead simply lay their eggs in a gravel bed and leave the young hatchlings to mature on their own. Male steelhead frequently breed with multiple female partners, possibly because more females than males die during the breeding period.

Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); inherits maternal/paternal territory

Female fish find suitable nest sites while their male mate guards the site from other interested males and predators. The female digs the nest (called a redd) with her anal fin and then descends upon it to position her vent and anal fin into the deepest part of the redd. The male joins her in a parallel position so that their vents are opposite each other. The male and female open their mouths, arch their backs, and deposit the eggs and milt (fish sperm) at the same time. The eggs are enveloped in a cloud of milt and are fertilized. Only a few seconds elapse from the time the female drops into the redd and fertilization occurs. The female then covers the nest with gravel and repeats the process again a few times until she has deposited all of her eggs.

Mating System: polygynous

Adult rainbow trout and steelhead lay their eggs in a series of nests in gravel. Collectively, the nests are called a redd. When they hatch, the hatchlings are still attached to, and survive on their yok sac. They remain in the protective gravel for about 2 to 3 weeks when they have shed their yolk sacs and are fit enough to survive in the open water. Juvenile fish tend to stick to shallow and side areas of the streams where there is protective cover and slow-moving currents. The remain in their native streams for 1 to 3 years while they grow fit enough to spawn or migrate to the ocean, in the case of steelheads.

Breeding interval: Rainbow trout breed every three to five years. Though steelhead are one of the only salmonids able to spawn twice in a lifetime, the return rate is very low, about 10-20%

Breeding season: Spawning occurs from March to July, depending on temperature and other climatic variables. Winter steelhead in California start spawning as early as January.

Range number of offspring: 200 to 8000.

Range time to hatching: 3 to 16 weeks.

Range time to independence: one to three years.

Range age at sexual or reproductive maturity (female): 3 to 11 years.

Range age at sexual or reproductive maturity (male): 3 to 11 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization (External ); oviparous

Average number of offspring: 3500.

Female rainbow trout and steelehead simply lay their eggs in a gravel bed and leave the young hatchlings to mature on their own. Male steelhead frequently breed with multiple female partners, possibly because more females than males die during the breeding period.

Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); inherits maternal/paternal territory

Spawns usually in spring (February-June), or later depending on water temperature and location. Lays 200-9000 eggs (Wydoski and Whitney 1979), which hatch in 3-4 weeks at 10-15 C. Fry emerge from gravel 2-3 weeks after hatching. Many are sexually mature in 2-3 years. See Stearley (1992) for a discussion of the historical ecology and life history evolution of Pacific salmons and trouts (Oncorhynchus).

Fish respond to magnetic fields: rainbow trout
 

The trigeminal cranial nerve of rainbow trout helps them detect magnetic fields by containing magnetosensitive nerve fibers.

   
  "In 1997, the first known magnetoreceptors -- directly linking magnetite to neural connections and activity -- were found in vertebrates. A team of zoologists from Auckland University, led by Dr. Michael Walker, had been studying this mysterious sense in trout, and knew that a region of its skull contained magnetite.

"Recording neural activity from that region, they discovered that a specific subgroup of nerve fibers within a branch of the trigeminal cranial nerve called the ros V nerve fired in response to changes in the surrounding magnetic field. They also found magnetite in a tissue layer directly beneath the trout's olfactory (smell) organs. When they injected a colored dye into the ros V nerve's newly exposed magnetosensitive fibers, the dye revealed that the fibers terminated and ramified all around the magnetite-containing cells within the trout's olfactory tissue." (Shuker 2001:46)
  Learn more about this functional adaptation.

Crystals create iridescent sheen: rainbow trout
 

The scales of a rainbow trout have a silvery shine due to guanine crystals.

   
  "The scales of a rainbow trout, reflective yet translucent. The silvery lustre is due to crystals of guanine, produced in the body as a waste product. The tiny black speckles are pigment cells, and at intervals there are large clusters of these where the pigment is distributed right across each cell, instead of only in the centre; here we get the large black patches which produce colour changes in response to hormones released during the breeding season - hence the name rainbow trout. The overlapping scales form a waterproof armour which is flexible enough to allow for the flexing of the body during swimming." (Foy and Oxford Scientific Films 1982:87)
  Learn more about this functional adaptation.

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 263 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.


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Barcode of Life Data Systems (BOLDS) Stats
Public Records: 263
Specimens with Barcodes: 324
Species With Barcodes: 1

Steelhead are endangered in Washington and California, and threatened in California, Oregon, Washington, and Idaho. Most of their decline has resulted from impacts to habitat and shrinking of spawning routes due to dams and other diversions. Siltation, caused by forestry practices, and erosion, caused by urban and agricultural development, has also impacted spawning beds.

IUCN Red List of Threatened Species: no special status

US Federal List: endangered

CITES: no special status

Steelhead are endangered in Washington and California, and threatened in California, Oregon, Washington, and Idaho. Most of their decline has resulted from impacts to habitat and shrinking of spawning routes due to dams and other diversions. Siltation, caused by forestry practices, and erosion, caused by urban and agricultural development, has also impacted spawning beds.

US Federal List: endangered

CITES: no special status

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Very large range; abundant; secure on a range-wide scale. See also information for the many subspecies and stocks (e.g., steelhead, redband trout, etc.).

Current Listing Status Summary

Status: Endangered
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: southern CA coast

Status: Threatened
Date Listed: 08/02/1999
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: upper Willamette R.

Status: Threatened
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: upper Columbia R. Basin

Status: Threatened
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: central CA coast

Status: Threatened
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: south central CA coast

Status: Threatened
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: Central Valley CA

Status: Threatened
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: lower Columbia R.

Status: Threatened
Date Listed: 08/02/1999
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: middle Columbia R.

Status: Threatened
Date Listed: 09/07/2000
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: northern CA

Status: Threatened
Date Listed: 06/17/1998
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: Snake R. Basin

Status: Under Review
Date Listed:
Lead Region:   National Marine Fisheries Service (Region 11)   
Where Listed: Klamath Mountains Province


Population detail:

Population location: All naturally spawned populations (and their progeny) in streams and tributaries to the Columbia R. between the Cowlitz and Wind Rivers, WA, inclusive, and the Willamette and Hood Rivers, OR, inclusive, excluding the Upper Willamette River Basin above Willamette Falls and excluding the Little and Big White Salmon Rivers in WA
Listing status: T

Population location: All naturally spawned populations (and their progeny) in the Upper Columbia R. Basin upstream from the Yakima R., WA, to the U.S./Canada border, and also including the Wells Hatchery stock
Listing status: T

Population location: U.S.A. (OR, WA) All naturally spawned populations in streams above and excluding the Wind R. in Washington, and the Hood R. in Oregon, upstream to, and including, the Yakima R. Excluded are steelhead from the Snake R. Basin
Listing status: T

Population location: All naturally spawned populations (and their progeny) in streams in the Snake R. Basin of southeast WA, northeast OR, and ID
Listing status: T

Population location: All naturally spawned populations and their progeny in river basins from Redwood Creek in Humboldt County, CA to the Gualala River in Mendocino County, CA (inclusive)
Listing status: T

Population location: All naturally spawned populations (and their progeny) in rivers from the Santa Maria R., San Luis Obispo County, CA (inclusive) to Malibu Cr., Los Angeles County, CA (inclusive)
Listing status: E

Population location: All naturally spawned populations (and their progeny) in streams from the Pajaro R. (inclusive) located in Santa Cruz County, CA, to (but not including) the Santa Maria R
Listing status: T

Population location: U.S.A. (OR) All naturally spawned winter-run populations in the Willamette R. and its tributaries from Willamette Falls to the Calapooia R., inclusive
Listing status: T

Population location: All naturally spawned populations (and their progeny) in streams from the Russian R. to Aptos Cr., Santa Cruz County, CA (inclusive), and the drainages of San Francisco and San Pablo Bays eastward to the Napa R. (inclusive), Napa County, CA, excluding the Sacramento-San Joaquin R. Basin of the Central Valley of CA
Listing status: T

Population location: All naturally spawned populations (and their progeny) in the Sacramento and San Joaquin Rivers and their tributaries, excluding San Francisco and San Pablo Bays and their tributaries
Listing status: T

For most current information and documents related to the conservation status and management of Oncorhynchus mykiss, see its USFWS Species Profile

Not Evaluated

Comments: On a range-wide scale, this species is not significantly threatened. However, many subspecies and populations face serious threats (see separate accounts).

Declines in winter steelhead stocks from the Siuslaw River north to Tillamook Bay, Oregon, may have resulted from deterioration of ocean feeding conditions, widespread use of hatchery stock, predation by marine mammals, and ocean drift-net fishing (Nehlsen et al. 1991). Declining winter catches on the Illinois River (tributary to the Rogue River), Oregon, since the mid-1970s have been attributed to water withdrawal for irrigation (Nehlsen et al. 1991). In the Columbia River basin, winter stocks are threatened by habitat degradation, main stem passage problems, and interactions with hatchery fish (Nehlson et al. 1991). Declines in several winter populations in the Puget Sound area of Washington have resulted from habitat degradation (e.g., water quality problems, siltation, and sedimentation); predation by sea lions has been reported as a problem for the Lake Washington population (Nehlsen et al. 1991). Whirling disease has caused population declines in some areas. The disease is caused by a protozoan pathogen (inadvertently introduced from Europe) and involves tubifex worms as an alternate host. Brown trout (Salmo trutta) are unaffected by the protozoan and serve as a reservoir.

Management Requirements: A management concern in the West: keeping rainbow trout out of waters inhabited by native salmonids such as cutthroat trout and Gila trout so that the native species maintain their genetic integrity.

Allendorf et al. (1997) proposed criteria for prioritizing Pacific salmon stocks for conservation; data limitations introduce subjectivity into the process, so expert judgment and peer review should be incorporated into the process.

Global Protection: Very many (>40) occurrences appropriately protected and managed

Comments: Many occurrences are in protected areas.

Rainbow trout have been introduced throughout the world, negatively impacting species of native freshwater fishes and, therefore, native fisheries.

These fish are one of the most popular game fishes around the world, leading to nearly global introduction. They are introduced to stimulate local angling and associated recreational economies. However, where they are introduced, they can outcompete native trout species.

Positive Impacts: food ; ecotourism

fisheries: highly commercial; aquaculture: commercial; gamefish: yes; price category: low; price reliability: reliable: based on ex-vessel price for this species

Rainbow trout have been introduced throughout the world, negatively impacting species of native freshwater fishes and, therefore, native fisheries.

These fish are one of the most popular game fishes around the world, leading to nearly global introduction. They are introduced to stimulate local angling and associated recreational economies. However, where they are introduced, they can outcompete native trout species.

Positive Impacts: food ; ecotourism

Comments: Important game fish. Various populations have been cultured and introduced due to unique qualities (e.g., large lake form Kamloops; Eagle Lake rainbow, adapted to alkaline waters and usually piscivorous; Arlee strain, noted for fast growth, disease resistance, and high catchability (Sublette et al. 1990). Used in carcinogen testing (Metcalfe 1989).

Species Impact: Smolt-to-adult survival of spring/summer run chinook salmon is negatively associated with releases of hatchery-reared steelhead in the Snake River (Levin and Williams 2002).

Comments: This highly variable species formerly was known as Salmo gairdneri, but this taxon is closely related to Pacific salmon and is conspecific with Asiatic steelhead (Oncorhynchus mykiss). For a complete taxonomic history, see Smith and Stearley (1989), Robins et al. (1991), and Behnke (1992).

"Redband" trout has been used as the name for nonanadromous populations adapted to harsh arid environments (Wishard et al. 1984); however, the term "redband" should not be used to imply a taxonomic relationship among all groups of rainbow trout in interior basins of Oregon and adjacent areas of Idaho, Nevada, and California (Wishard et al. 1984, Currens et al. 1990). Currens et al. (1990) found no evidence that all isolated groups of rainbow trout with plesiomorphic characteristics in the White River, Oregon desert basins, and northern California represent a monophyletic group.

Behnke (1992) included in O. mykiss three major groups: (1) the redband trout of the Columbia River basin east of the Cascade Mountains, and in upper Fraser River basin and the Athabasca headwaters of the Mackenzie River basin (subspecies gairdneri); (2) the redband trout of the Sacramento River basin, which he regarded as comprising two Kern River drainage subspecies (aguabonita and gilberti), plus the McCloud River subspecies (provisionally denoted as subspecies stonei); and (3) the coastal rainbow trout (nominal subspecies irideus of North America and mykiss of eastern Asia, though no known taxonomic characters separate mykiss from irideus). Behnke concluded that other forms, such as the redband trout native to Oregon desert basins, Upper Klamath Lake, the Pit River drainage, and Eagle Lake, California, cannot be consistently distinguished from the three groups listed above. He noted that their classification is a matter of personal preference and professional judgment. However, in the same publication, he stated that "the trout specialized for lacustrine conditions in Klamath Lake...is well differentiated from other groups of both redband and coastal rainbow trout and could be recognized as a subspecies, O. m. newberrii."

Hatchery rainbow trout derived mainly from coastal steelhead are widely stocked throughout the ranges of western trout (Behnke 1992). These hatchery fishes have led to hybridization with most populations of resident redband trout in the upper Sacramento River basin, the Oregon desert basins, and much of the Columbia River basin (Behnke 1992).

Oncorhynchus mykiss freely interbreeds with cutthroat trout (O. clarki) and Gila trout (O. gilae), producing fertile offspring (Sublette et al. 1990).