Oncorhynchus mykiss - (Walbaum, 1792)
Rainbow Trout or Steelhead
Synonym(s): Parasalmo mykiss ;Salmo gairdneri
Taxonomic Status: Accepted
Related ITIS Name(s): Oncorhynchus mykiss (Walbaum, 1792) (TSN 161989)
French Common Names: truite arc-en-ciel
Unique Identifier: ELEMENT_GLOBAL.2.105164
Element Code: AFCHA02090
Informal Taxonomy: Animals, Vertebrates - Fishes - Bony Fishes - Salmon and Trouts
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Actinopterygii Salmoniformes Salmonidae Oncorhynchus
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. 1991. Common and scientific names of fishes from the United States and Canada. American Fisheries Society, Special Publication 20. 183 pp.
Concept Reference Code: B91ROB01NAUS
Name Used in Concept Reference: Oncorhynchus mykiss
Taxonomic 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).
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 10May2016
Global Status Last Changed: 12Sep1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: 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.).
Nation: United States
National Status: N5 (05Dec1996)
Nation: Canada
National Status: N5 (13Sep2011)

U.S. & Canada State/Province Status
United States Alabama (SNA), Alaska (S4), Arizona (SNA), Arkansas (SNA), California (SNR), Colorado (SNA), Connecticut (SNA), Delaware (SNA), Georgia (SNA), Hawaii (SNA), Idaho (S4), Illinois (SNA), Indiana (SNA), Iowa (SNA), Kansas (SNA), Kentucky (SNA), Maine (SNA), Maryland (SNA), Massachusetts (SNA), Michigan (SNA), Minnesota (SNA), Mississippi (SNA), Missouri (SNA), Montana (S5), Navajo Nation (SNA), Nebraska (SNA), Nevada (S2), New Hampshire (SNA), New Jersey (SNA), New Mexico (SNA), New York (SNA), North Carolina (SNA), North Dakota (SNA), Ohio (S5), Oklahoma (SNA), Oregon (S5), Pennsylvania (SNA), Rhode Island (SNA), South Dakota (SNA), Tennessee (SNA), Texas (SNA), Utah (SNA), Vermont (SNA), Virginia (SNA), Washington (S5), West Virginia (SNA), Wisconsin (SNA), Wyoming (SNA)
Canada Alberta (S1), British Columbia (S5), Manitoba (SNA), New Brunswick (SNA), Newfoundland Island (SNA), Northwest Territories (SNA), Nova Scotia (SNA), Ontario (SNA), Prince Edward Island (SNA), Quebec (SNA), Saskatchewan (SNA), Yukon Territory (S3)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS
Comments on USESA: Subspecies whitei is listed by the USFWS as Threatened (as O. aguabonita whitei).

The following steelhead populations (ESUs) are listed under the U.S. Endangered Species Act: Endangered: Southern California, Upper Columbia River; Threatened: Central California Coast, South-Central California Coast, Snake River Basin, Lower Columbia River, California Central Valley, Upper Willamette River (winter run), Middle Columbia River, Puget Sound ESU, Northern California ESU. The Klamath Mountains Province ESU is under review in the candidate process for listing under the U.S. Endangered Species Act. The Oregon Coast ESU is a NMFS species of concern.

McCloud River redband trout and Middle Columbia River Steelhead are Candidates for listing under the U.S. Endangered Species Act.

NMFS (Federal Register, 14 May 1999) determined that listing of summer steelhead in the Middle Fork of the Eel River, California, is not warranted.

USFWS (1998) found that petitioned listing of redband trout as threatened or endangered in the Great Basin may be warranted; a status review was initiated. Part of the status review is the consideration of whether one or multiple ESUs would be recognized and listed. USFWS (Federal Register, 20 March 2000) determined that listing of Great Basin redband trout in southeastern Oregon, northeastern California, and northwestern Nevada is not warranted.

USFWS (2002) found that a petition to list O. mykiss aguabonita under the U.S. Endangered Species Act presented substantial information indicating that listing may be warranted; a status review was initiated.

NMFS (Federal Register, 39 March 2006) proposed Threatened status for the Puget Sound population.

Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Candidate (High)

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: 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 throughout 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).

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: > 300
Number of Occurrences 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.

Population Size: >1,000,000 individuals
Population Size 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).

Number of Occurrences with Good Viability/Integrity: Very many (>125)

Overall Threat Impact 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.

Short-term Trend Comments: Of 867 steelhead stocks in British Columbia and the Yukon, Slaney et al. (1996) categorized 9 as extirpated, 8 as high risk, 10 as moderate risk, 143 as special concern, 282 as unthreatened, and 415 as of unknown status. Many winter steelhead populations are at very low levels; populations have declined in nearly all streams in central and southern California (see Nehlsen et al. 1991 for further details). Winter steelhead stocks from Siuslaw River north to Tillamook Bay, Oregon, have been declining since 1990 (Nehlsen et al. 1991). In the Illinois River (tributary to the Rogue River), Oregon, winter steelhead catches have declined since the mid-1970s (Nehlsen et al. 1991). Several winter populations in the Puget Sound area of Washington have also experienced declines (Nehlsen et al. 1991).

Other NatureServe Conservation Status Information

Distribution
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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 throughout 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).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, ALexotic, ARexotic, AZexotic, CA, COexotic, CTexotic, DEexotic, GAexotic, HIexotic, IAexotic, ID, ILexotic, INexotic, KSexotic, KYexotic, MAexotic, MDexotic, MEexotic, MIexotic, MNexotic, MOexotic, MSexotic, MT, NCexotic, NDexotic, NEexotic, NHexotic, NJexotic, NMexotic, NNexotic, NV, NYexotic, OH, OKexotic, OR, PAexotic, RIexotic, SDexotic, TNexotic, TXexotic, UTexotic, VAexotic, VTexotic, WA, WIexotic, WVexotic, WYexotic
Canada AB, BCnative and exotic, MBexotic, NBexotic, NFexotic, NSexotic, NTexotic, ONexotic, PEexotic, QCexotic, SKexotic, YT

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
CA Alameda (06001), Amador (06005), Butte (06007), Calaveras (06009), Colusa (06011), Contra Costa (06013), Del Norte (06015), El Dorado (06017), Fresno (06019), Glenn (06021), Humboldt (06023), Lassen (06035), Los Angeles (06037), Madera (06039), Marin (06041), Mendocino (06045), Merced (06047), Modoc (06049), Monterey (06053), Napa (06055), Nevada (06057), Placer (06061), Riverside (06065), Sacramento (06067), San Diego (06073), San Joaquin (06077), San Luis Obispo (06079), San Mateo (06081), Santa Barbara (06083), Santa Clara (06085), Santa Cruz (06087), Shasta (06089), Siskiyou (06093), Solano (06095), Sonoma (06097), Stanislaus (06099), Sutter (06101), Tehama (06103), Trinity (06105), Tulare (06107), Tuolumne (06109), Ventura (06111), Yolo (06113), Yuba (06115)
MT Flathead (30029), Lincoln (30053)
NV Elko (32007), Washoe (32031)
OR Baker (41001)*, Benton (41003), Clackamas (41005), Clatsop (41007), Columbia (41009), Coos (41011), Crook (41013), Curry (41015), Douglas (41019), Gilliam (41021), Grant (41023), Harney (41025), Hood River (41027), Jackson (41029), Jefferson (41031), Josephine (41033), Klamath (41035)*, Lake (41037), Lane (41039), Lincoln (41041), Linn (41043), Malheur (41045)*, Marion (41047), Morrow (41049), Multnomah (41051), Polk (41053), Sherman (41055), Tillamook (41057), Umatilla (41059), Union (41061), Wallowa (41063), Wasco (41065), Washington (41067), Wheeler (41069), Yamhill (41071)
WA Asotin (53003)+, Benton (53005)+, Chelan (53007)+, Clallam (53009)+, Clark (53011)+, Columbia (53013)+, Cowlitz (53015)+, Douglas (53017)+, Franklin (53021)+, Garfield (53023)+, Grays Harbor (53027)+, Jefferson (53031)+, King (53033)+, Kitsap (53035)+, Kittitas (53037)+, Klickitat (53039)+, Lewis (53041)+, Mason (53045)+, Okanogan (53047)+, Pacific (53049)+, Pierce (53053)+, Skagit (53057)+, Skamania (53059)+, Snohomish (53061)+, Thurston (53067)+, Wahkiakum (53069)+, Walla Walla (53071)+, Whatcom (53073)+, Whitman (53075)+, Yakima (53077)+
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Middle Savannah (03060106)
16 Rock (16040106)+, Little Humboldt (16040109)+, Upper Quinn (16040201)+*, Long-Ruby Valleys (16060007)+
17 Upper Kootenai (17010101)+, Fisher (17010102)+, Yaak (17010103)+, Lower Kootenai (17010104)+, Stillwater (17010210)+, Priest (17010215), Pend Oreille (17010216), Upper Spokane (17010305), Hangman (17010306), Lower Spokane (17010307), Little Spokane (17010308), Franklin D. Roosevelt Lake (17020001), Kettle (17020002), Colville (17020003), Sanpoil (17020004), Chief Joseph (17020005), Okanogan (17020006), Similkameen (17020007), Methow (17020008), Lake Chelan (17020009), Upper Columbia-Entiat (17020010), Wenatchee (17020011), Moses Coulee (17020012), Upper Crab (17020013), Banks Lake (17020014), Lower Crab (17020015), Upper Columbia-Priest Rapids (17020016), Upper Yakima (17030001), Naches (17030002), Lower Yakima, Washington (17030003), Upper Snake-Rock (17040212), Salmon Falls (17040213), C. J. Idaho (17050101), Bruneau (17050102), Middle Snake-Succor (17050103), Upper Owyhee (17050104), South Fork Owyhee (17050105)+, East Little Owyhee. Nevada, (17050106), Middle Owyhee (17050107), Jordan (17050108)+, Crooked-Rattlesnake (17050109), Lower Owyhee (17050110)+, North and Middle Forks Boise (17050111), Boise-Mores (17050112), South Fork Boise (17050113), Lower Boise (17050114), Middle Snake-Payette (17050115), Upper Malheur (17050116)+, Lower Malheur (17050117)+, Bully (17050118), Willow (17050119), South Fork Payette (17050120), Middle Fork Payette (17050121), Payette (17050122), North Fork Payette (17050123), Weiser (17050124), Brownlee Reservoir (17050201), Burnt (17050202), Powder (17050203)+, Hells Canyon (17060101)+, Imnaha (17060102)+, Lower Snake-Asotin (17060103)+, Upper Grande Ronde (17060104)+, Wallowa (17060105)+, Lower Grande Ronde (17060106)+, Lower Snake-Tucannon (17060107), Palouse (17060108), Rock (17060109), Lower Snake (17060110), Upper Salmon (17060201), Middle Salmon-Panther (17060203), Lemhi (17060204), Upper Middle Fork Salmon (17060205), Lower Middle Fork Salmon (17060206), Middle Salmon-Chamberlain (17060207), South Fork Salmon (17060208), Lower Salmon (17060209), Little Salmon (17060210), Upper Selway (17060301), Lower Selway (17060302), Lochsa (17060303), Middle Fork Clearwater (17060304), South Fork Clearwater (17060305), Clearwater (17060306), Upper North Fork Clearwater (17060307), Lower North Fork Clearwater (17060308), Middle Columbia-Lake Wallula (17070101)+, Walla Walla (17070102)+, Umatilla (17070103)+, Willow (17070104)+, Middle Columbia-Hood (17070105)+, Klickitat (17070106), Upper John Day (17070201)+, North Fork John Day (17070202)+, Middle Fork John Day (17070203)+, Lower John Day (17070204)+, Upper Deschutes (17070301), Little Deschutes (17070302), Beaver-South Fork (17070303)+, Upper Crooked (17070304)+, Lower Crooked (17070305)+, Lower Deschutes (17070306)+, Trout (17070307)+, Lower Columbia-Sandy (17080001)+, Lewis (17080002), Lower Columbia-Clatskanie (17080003)+, Upper Cowlitz (17080004), Lower Cowlitz (17080005), Lower Columbia (17080006)+, Middle Fork Willamette (17090001), Coast Fork Willamette (17090002), Upper Willamette (17090003)+, Mckenzie (17090004), North Santiam (17090005)+, South Santiam (17090006)+, Middle Willamette (17090007)+, Yamhill (17090008)+, Molalla-Pudding (17090009)+, Tualatin (17090010)+, Clackamas (17090011)+, Lower Willamette (17090012)+, Hoh-Quillayute (17100101), Queets-Quinault (17100102), Upper Chehalis (17100103), Lower Chehalis (17100104), Grays Harbor (17100105), Willapa Bay (17100106), Necanicum (17100201)+, Nehalem (17100202)+, Wilson-Trusk-Nestuccu (17100203)+, Siletz-Yaquina (17100204)+, Alsea (17100205)+, Siuslaw (17100206)+, Siltcoos (17100207)+, North Umpqua (17100301)+, South Umpqua (17100302)+, Umpqua (17100303)+, Coos (17100304)+, Coquille (17100305)+, Sixes (17100306)+, Upper Rogue (17100307)+, Middle Rogue (17100308)+, Applegate (17100309)+, Lower Rogue (17100310)+, Illinois (17100311)+, Chetco (17100312)+, Fraser (17110001), Strait of Georgia (17110002), San Juan Islands (17110003), Nooksack (17110004), Upper Skagit (17110005), Sauk (17110006), Lower Skagit (17110007), Stillaguamish (17110008), Skykomish (17110009), Snoqualmie (17110010), Snohomish (17110011), Lake Washington (17110012), Duwamish (17110013), Puyallup (17110014), Nisqually (17110015), Deschutes (17110016), Skokomish (17110017), Hood Canal (17110018), Puget Sound (17110019), Dungeness-Elwha (17110020), Crescent-Hoko (17110021), Harney-Malheur Lakes (17120001)+, Silvies (17120002)+, Donner Und Blitzen (17120003)+, Silver (17120004)+, Summer Lake (17120005)+, Lake Abert (17120006)+, Warner Lakes (17120007)+, Guano (17120008)+
18 Smith (18010101)+, Mad-Redwood (18010102)+, Upper Eel (18010103), Middle Fork Eel (18010104)+, Lower Eel (18010105)+, South Fork Eel (18010106), Mattole (18010107)+, Big-Navarro-Garcia (18010108)+, Gualala-Salmon (18010109)+, Russian (18010110)+, Bodega Bay (18010111), Williamson (18010201)+, Sprague (18010202)+, Upper Klamath Lake (18010203)+, Lost (18010204), Butte (18010205), Upper Klamath (18010206)+, Shasta (18010207), Scott (18010208), Lower Klamath (18010209)+, Salmon (18010210)+, Trinity (18010211)+, South Fork Trinity (18010212)+, Goose Lake (18020001)+, Upper Pit (18020002), Lower Pit (18020003)+, Mccloud (18020004)+, Sacramento headwaters (18020005), Sacramento-Lower Cow-Lower Clear (18020101), Lower Cottonwood (18020102), Sacramento-Lower Thomes (18020103), Sacramento-Stone Corral (18020104)+, Lower Butte (18020105), Lower Feather (18020106), Lower Yuba (18020107), Lower Bear (18020108), Lower Sacramento (18020109), Lower Cache (18020110), Lower American (18020111)+, Sacramento-Upper Clear (18020112), Cottonwood headwaters (18020113), Upper Elder-Upper Thomes (18020114), Upper Stony (18020115)+, Upper Cache (18020116), Upper Putah (18020117), Upper Cow-Battle (18020118), Mill-Big Chico (18020119), Upper Butte (18020120), North Fork Feather (18020121), East Branch North Fork Feather (18020122), Middle Fork Feather (18020123), Honcut headwaters (18020124), Upper Yuba (18020125)+, Upper Bear (18020126)+, Upper Coon-Upper Auburn (18020127), North Fork American (18020128), South Fork American (18020129), Cow Creek (18020151)+, Cottonwood Creek (18020152)+, Battle Creek (18020153)+, Clear Creek-Sacramento River (18020154)+, Paynes Creek-Sacramento River (18020155)+, Thomes Creek-Sacramento River (18020156)+, Big Chico Creek-Sacramento River (18020157)+, Butte Creek (18020158)+, Honcut Headwaters-Lower Feather (18020159)+, Upper Coon-Upper Auburn (18020161)+, Upper Putah (18020162)+, Lower Sacramento (18020163)+, Upper Kern (18030001)+, South Fork Kern (18030002)+, Middle Kern-Upper Tehachapi- (18030003), Upper Poso (18030004), Upper Deer-Upper White (18030005), Upper Tule (18030006), Upper Kaweah (18030007), Mill (18030008), Upper Dry (18030009), Upper King (18030010), Upper Los Gatos-Avenal (18030011), Tulare-Buena Vista Lakes (18030012)*, Middle San Joaquin-Lower (18040001)+, Middle San Joaquin-Lower (18040002)+, San Joaquin Delta (18040003)+, Lower Calaveras-Mormon Slough (18040004), Lower Cosumnes-Lower Mokelumne (18040005), Upper San Joaquin (18040006), Upper Chowchilla-Upper Fresno (18040007)+, Upper Merced (18040008)+, Upper Tuolumne (18040009)+, Upper Stanislaus (18040010)+, Upper Calaveras (18040011)+, Upper Mokelumne (18040012)+, Upper Cosumnes (18040013)+, Panoche-San Luis Reservoir (18040014), Rock Creek-French Camp Slough (18040051)+, Suisun Bay (18050001)+, San Pablo Bay (18050002)+, Coyote (18050003), San Francisco Bay (18050004)+, Tomales-Drake Bays (18050005)+, San Francisco Coastal South (18050006)+, San Lorenzo-Soquel (18060001)+, Pajaro (18060002)+, Carrizo Plain (18060003), Estrella (18060004), Salinas (18060005)+, Central Coastal (18060006)+, Cuyama (18060007), Santa Maria (18060008)+, San Antonio (18060009), Santa Ynez (18060010)+, Alisal-Elkhorn Sloughs (18060011), Carmel (18060012)+, Santa Barbara Coastal (18060013)+, Ventura (18070101)+, Santa Clara (18070102)+, Calleguas (18070103)+, Santa Monica Bay (18070104)+, Los Angeles (18070105), San Gabriel (18070106), Seal Beach (18070201), San Jacinto (18070202), Santa Ana (18070203), Newport Bay (18070204), Aliso-San Onofre (18070301)+, Santa Margarita (18070302), San Luis Rey-Escondido (18070303), San Diego (18070304), Cottonwood-Tijuana (18070305), Honey-Eagle Lakes (18080003)+, Antelope-Fremont Valleys (18090206), Mojave (18090208)
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
U.S. Distribution by Watershed (based on multiple information sources) Help
Ecology & Life History
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Basic Description: A partially anadromous salmonid.
Diagnostic Characteristics: 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).
Reproduction Comments: 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).
Ecology Comments: 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).
Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: Y
Mobility and Migration Comments: 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.
Marine Habitat(s): Near shore, Pelagic
Estuarine Habitat(s): Bay/sound, Lagoon, River mouth/tidal river
Riverine Habitat(s): BIG RIVER, CREEK, High gradient, Low gradient, MEDIUM RIVER, Moderate gradient, Pool, Riffle
Lacustrine Habitat(s): Deep water, Shallow water
Special Habitat Factors: Benthic
Habitat 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).

Adult Food Habits: Invertivore, Piscivore
Immature Food Habits: Invertivore, Piscivore
Food 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.
Phenology Comments: May feed at any time throughout a 24-hour period, but usually feeds most actively around dusk.
Length: 100 centimeters
Economic Attributes
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Economic 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).
Management Summary
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Species Impacts: 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).
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.

Population/Occurrence Delineation
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Group Name: Fishes with Anadromous Populations

Use Class: Freshwater
Subtype(s): Rearing & Migration Area, Spawning & Rearing Area
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including eggs and larvae) in appropriate habitat. For anadromous populations, occurrences are based on collection or reliable observation and documentation of one or more spawning adults, redds, other evidence of spawning, or larvae or juveniles in appropriate spawning/rearing habitat.
Mapping Guidance: Conceptually, the occurrence includes the entire freshwater area used by the population, including spawning, rearing, and migration areas. For anadromous populations, an occurrence should extend from the most upstream spawning areas downstream to the ocean. However, it is desirable (and practical) to subdivide this sometimes very large occurrence, sometimes overlapping with many other spaghetti-like occurrences extending down from the upstream spawning areas to the ocean, into separate source features or sub-occurrences, labeled with a feature label that reflects the life history stage in that area. Moreover, it may make practical sense to treat the areas downstream of spawning and/or rearing areas as a mixed element animal assemblage: Freshwater Salmon Migration Corridor. This negates the need to separately map each occurrence down to the ocean from its upstream spawning location. Information about areas with different life-history uses can be generated by using best professional judgment by district or regional fish biologists and may or may not incorporate specific locational information from spawning surveys or other surveys.
Separation Barriers: Dam lacking a suitable fishway; high waterfall; upland habitat that is very unlikely to be submerged even during periods of exceptionally high water (e.g., 100-year flood or 1% flood).
Alternate Separation Procedure: For anadromous populations and migratory populations that have distinct and separate spawning and nonspawning areas, the area used by each population whose spawning area is separated by a gap of at least 10 stream-km from other spawning areas within a stream system is potentially mappable as a distinct occurrence that extends down to the ocean (but see mapping guidance), regardless of whether the spawning areas are in the same or different tributaries.

For other (e.g., nonanadromous) populations in streams, separation distance is 10 stream-km for both suitable and unsuitable habitat. However, if it is known that the same population occupies sites separated by more than 10 km (e.g., this may be common for migratory, nonanadromous populations), those sites should be included within the same occurrence. In lakes, occurrences include all suitable habitat that is presumed to be occupied (based on expert judgment), even if documented collection/observation points are more than 10 km apart. Separate sub-occurrences or source features may usefully document locations of critical spawning areas within a lake.

Separation Justification: The separation distance is arbitrary but was selected to ensure that occurrences are of manageable size but not too small. Because of the difficulty in defining suitable versus unsuitable habitat, especially with respect to dispersal, and to simplify the delineation of occurrences, a single separation distance is used regardless of habitat quality.

"Restricted movement is the norm in populations of stream salmonids during nonmigratory periods," but there is considerable variation in movements within and among species (Rodriguez 2002). Redband trout in Montana had October-December home ranges of 5-377 m, consistent with small movements observed for radio-tagged brook trout and cutthroat trout during fall and winter (Muhlfeld et al. 2001). For nonanadromous populations, little is known about juvenile dispersal (e.g., how far fishes may move between between their embryonic developmental habitat and eventual spawning site).

In summer and fall, radio-tagged cutthroat trout in Strawberry Reservoir in Utah had single-month home ranges that were usually about 3-4 km in maximum length (Baldwin et al. 2002). In the Blackfoot River drainage, Montana, radio-tagged westslope cutthroat trout moved 3-72 km (mean 31 km) to access spawning tributaries (Schmetterling 2001). This indicates that migratory but nonanadromous populations may use extensive areas and that one should not invoke the 10-km separation distance without considering the full extent of the population.

Date: 25Nov2009
Author: Hammerson, G., and L. Master
Notes: This Specs Group comprises fish species that include anadromous populations (may also include nonanadromous populations), such as lampreys, sturgeons, herrings, shads, salmonids, and smelts.

Criteria for marine occurrences (Location Use Class: Marine) have not yet been established. These may not be needed for marine occurrences of species that likely will be dealt with as mixed element assemblages (e.g., Salmonid Marine Concentration Area).

Feature Descriptor Definitions:

Spawning Area: area used for spawning but not for rearing or migration.

Rearing Area: area used for larval/juvenile development but not for spawning or migration.

Migration Corridor: area used for migration but not for rearing or spawning.

Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 15Jan2008
Management Information Edition Date: 12Dec2002
Element Ecology & Life History Edition Date: 05Jan2004
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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References for Watershed Distribution Map
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