The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Salmo trutta
Salmo trutta
(Brown Trout)

Copyright Info
Salmo trutta Linnaeus, 1758

Common name: Brown Trout

Synonyms and Other Names: Salmo fario, S. lacustris; von Behr trout, Loch Leven trout, German brown trout

Taxonomy: available through www.itis.govITIS logo

Injurious: This species is listed by the U.S. Fish and Wildlife Service as injurious wildlife.

Identification: Brown Trout has an elongated body that tapers at both ends. The body has a brown or yellow-brown hue with numerous spots below the lateral line. The spots on the upper body are typically black and surrounded by pale halos. Spots on the lower body are red. Head is small and pointed, with a large mouth that extends primarily after the eye. Brown Trout has 3–4 dorsal spines, 3–4 anal spines, and the adipose fin has a red margin. Scott and Crossman (1973); Page and Burr (1991); Jenkins and Burkhead (1994).

Size: 103 cm

Native Range: Europe, northern Africa, and western Asia (Page and Burr 1991).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Salmo trutta are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AL197119962Middle Coosa; Upper Tallapoosa
AZ1880200619Chevelon Canyon; Grand Canyon; Havasu Canyon; Lake Mead; Little Colorado Headwaters; Lower Colorado Region; Lower Colorado-Marble Canyon; Lower Lake Powell; Lower Little Colorado; Lower Verde; Middle Little Colorado; Paria; Rillito; San Francisco; Silver; Tonto; Upper Gila-San Carlos Reservoir; Upper Salt; Upper Verde
AR197320218Beaver Reservoir; Bull Shoals Lake; Lake Conway-Point Remove; Little Missouri; Little Red; Middle White; North Fork White; Spring
CA1884202351Butte; California Region; Clear Creek-Sacramento River; Cottonwood Creek; Crowley Lake; East Branch North Fork Feather; East Walker; Honey-Eagle Lakes; Klamath; Lake Tahoe; Lower Eel; Lower Pit; Mad-Redwood; McCloud; Middle Fork Feather; Middle San Joaquin-Lower Chowchilla; Mojave; Mono Lake; Newport Bay; North Fork American; North Fork Feather; Owens Lake; Sacramento Headwaters; Salmon; San Francisco Bay; San Joaquin; Santa Ana; Santa Clara; Santa Margarita; Scott; South Fork American; South Fork Kern; Surprise Valley; Trinity; Truckee; Upper Cache; Upper Carson; Upper Kaweah; Upper Kern; Upper King; Upper Klamath; Upper Merced; Upper Mokelumne; Upper Pit; Upper Sacramento; Upper San Joaquin; Upper Stanislaus; Upper Tule; Upper Tuolumne; Upper Yuba; West Walker
CO1880202443Animas; Arkansas Headwaters; Big Thompson; Blue; Cache La Poudre; Clear; Colorado Headwaters; Conejos; Crow; Eagle; East-Taylor; Fountain; Gunnison; Huerfano; Little Snake; Lower Green-Diamond; Lower Gunnison; Lower Yampa; Middle South Platte-Cherry Creek; North Platte; North Platte Headwaters; Piedra; Purgatoire; Republican; Rio Grande Headwaters; Roaring Fork; San Luis; San Miguel; South Fork Republican; South Platte; South Platte Headwaters; St. Vrain; Tomichi; Uncompahgre; Upper Arkansas; Upper Arkansas-Lake Meredith; Upper Green-Flaming Gorge Reservoir; Upper Gunnison; Upper Laramie; Upper North Platte; Upper San Juan; Upper South Platte; White - Yampa
CT186520208Farmington River; Housatonic; New England Region; Outlet Connecticut River; Quinebaug River; Saugatuck; Shetucket River; Thames
DE188819923Brandywine-Christina; Delaware Bay; Mid Atlantic Region
FL198419841South Atlantic-Gulf Region
GA1962202016Apalachicola Basin; Conasauga; Coosawattee; Etowah; Hiwassee; Little; Middle Chattahoochee-Lake Harding; Middle Tennessee-Chickamauga; Ocoee; Savannah; South Atlantic-Gulf Region; Tugaloo; Upper Chattahoochee; Upper Coosa; Upper Little Tennessee; Upper Savannah
ID1882202251American Falls; Bear Lake; Beaver-Camas; Big Lost; Big Wood; Blackfoot; Boise-Mores; Brownlee Reservoir; C.J. Strike Reservoir; Camas; Clearwater; Hells Canyon; Idaho Falls; Lake Walcott; Little Wood; Lochsa; Lower Bear; Lower Bear-Malad; Lower Boise; Lower Clark Fork; Lower Henrys; Lower Salmon; Lower Snake-Asotin; Medicine Lodge; Middle Bear; Middle Fork Clearwater; Middle Kootenai; Middle Snake-Boise; Middle Snake-Succor; Moyie; North Fork Payette; Pacific Northwest Region; Palisades; Palouse; Payette; Pend Oreille Lake; Portneuf; Priest; Raft; Salmon Falls; South Fork Boise; Spokane; St. Joe; Teton; Upper Henrys; Upper North Fork Clearwater; Upper Salmon; Upper Snake-Rock; Upper Spokane; Weiser; Willow
IL1928202110Apple-Plum; Chicago; Kishwaukee; Lake Michigan; Lower Fox; Lower Rock; Middle Rock; Pecatonica; Upper Fox; Upper Illinois
IN194520016Chicago; Kankakee; Little Calumet-Galien; Lower East Fork White; Ohio Region; St. Joseph
IA1980202023Apple-Plum; Big Papillion-Mosquito; Coon-Yellow; Grant-Little Maquoketa; Little Sioux; Lower Cedar; Lower Iowa; Maple; Maquoketa; Middle Cedar; North Raccoon; North Skunk; Platte; Rock; Shell Rock; South Raccoon; Turkey; Upper Des Moines; Upper Grand; Upper Iowa; Upper Wapsipinicon; West Nodaway; Winnebago
KY1975200113Barren; Kentucky; Little Sandy; Little Scioto-Tygarts; Lower Kentucky; Ohio Brush-Whiteoak; Rough; South Fork Kentucky; Upper Cumberland; Upper Cumberland-Lake Cumberland; Upper Green; Upper Kentucky; Upper Levisa
ME1885202017Dead River; Lower Androscoggin River; Lower Kennebec River; Maine Coastal; Mattawamkeag River; Meduxnekeag River; New England Region; Passamaquoddy Bay-Bay of Fundy; Penobscot River; Piscataqua-Salmon Falls; Piscataquis River; Presumpscot; Saco River; Saint Croix River; St. George-Sheepscot; St. John; Upper Androscoggin River
MD1903202315Cacapon-Town; Chester-Sassafras; Choptank; Conococheague-Opequon; Gunpowder-Patapsco; Lower Susquehanna; Mid Atlantic Region; Middle Potomac-Anacostia-Occoquan; Middle Potomac-Catoctin; Monocacy; North Branch Potomac; Patuxent; Potomac; Upper Chesapeake; Youghiogheny
MA1953202018Ashuelot River-Connecticut River; Cape Cod; Charles; Chicopee River; Concord River; Deerfield River; Farmington River; Housatonic; Hudson-Hoosic; Merrimack River; Middle Hudson; Millers River; Nashua River; New England; New England Region; Quinebaug River; Westfield River; Winnipesaukee River
MI1883202140Au Gres-Rifle; Au Sable; Bad-Montreal; Betsie-Platte; Betsy-Chocolay; Black-Macatawa; Black-Presque Isle; Boardman-Charlevoix; Brule; Cheboygan; Dead-Kelsey; Detroit; Escanaba; Fishdam-Sturgeon; Flint; Great Lakes Region; Huron; Kalamazoo; Keweenaw Peninsula; Lake Huron; Lake Michigan; Lake St. Clair; Lake Superior; Lone Lake-Ocqueoc; Lower Grand; Manistee; Manistique River; Menominee; Michigamme; Muskegon; Ontonagon; Pere Marquette-White; Pine; St. Clair; Sturgeon; Thornapple; Thunder Bay; Tittabawassee; Upper Grand; Upper Wisconsin
MN1920202244Baptism-Brule; Beartrap-Nemadji; Beaver-Lester; Big Fork; Buffalo-Whitewater; Cannon; Clearwater; Clearwater-Elk; Cloquet; Coon-Yellow; Crow Wing; Des Moines Headwaters; Eastern Wild Rice; Elk-Nokasippi; Hawk-Yellow Medicine; Kettle; Lac Qui Parle; Lake Superior; Little Fork; Lower Minnesota; Lower Rainy; Lower St. Croix; Middle Minnesota; Minnesota; Mississippi Headwaters; Otter Tail; Platte-Spunk; Prairie-Willow; Rainy; Rainy Headwaters; Red; Red Lakes; Redwood; Root; Roseau; Rush-Vermillion; Sauk; South Fork Crow; St. Croix; St. Louis; Twin Cities; Upper Iowa; Upper St. Croix; Zumbro
MO190320157Bull Shoals Lake; Current; Harry S. Truman Reservoir; Lower Gasconade; Meramec; Niangua; North Fork White
MT1889202051Beaverhead; Belt; Big Hole; Big Horn Lake; Bitterroot; Blackfoot; Boulder; Bullwhacker-Dog; Clarks Fork Yellowstone; Fisher; Flathead Lake; Flatwillow; Flint-Rock; Fort Peck Reservoir; Gallatin; Jefferson; Judith; Lower Bighorn; Lower Clark Fork; Lower Tongue; Lower Yellowstone; Lower Yellowstone; Lower Yellowstone-Sunday; Madison; Marias; Marias; Middle Clark Fork; Middle Kootenai; Middle Milk; Missouri-Poplar; Musselshell; Pend Oreille; Prairie Elk-Wolf; Red Rock; Ruby; Shields; Smith; Stillwater; Sun; Teton; Upper Clark Fork; Upper Missouri; Upper Missouri; Upper Missouri-Dearborn; Upper Musselshell; Upper Tongue; Upper Yellowstone; Upper Yellowstone; Upper Yellowstone-Lake Basin; Upper Yellowstone-Pompeys Pillar; Yellowstone Headwaters
NE1903201921Calamus; Dismal; Hat; Horse; Lewis and Clark Lake; Lower Lodgepole; Lower Niobrara; Lower North Platte; Middle Niobrara; Middle North Platte-Scotts Bluff; Middle Platte-Buffalo; Middle Republican; Missouri Region; Niobrara Headwaters; Snake; South Loup; Upper Elkhorn; Upper Lodgepole; Upper Middle Loup; Upper Niobrara; Upper White
NV1906202032Black Rock Desert; Carson; Central Lahontan; Central Nevada Desert Basins; Diamond-Monitor Valleys; Fish Lake-Soda Spring Valleys; Gabbs Valley; Hamlin-Snake Valleys; Havasu-Mohave Lakes; Imperial Reservoir; Lake Mead; Lake Tahoe; Long-Ruby Valleys; Lower Humboldt; Meadow Valley Wash; Middle Carson; Northern Big Smoky Valley; Pacific Northwest; Pilot-Thousand Springs, Nevada, Utah; Pyramid-Winnemucca Lakes; Reese; Salmon Falls; Sand Spring-Tikaboo Valleys; Smoke Creek Desert; Spring-Steptoe Valleys; Thousand-Virgin; Truckee; Upper Carson; Upper Quinn; Walker Lake; West Walker; White
NH1885202017Ammonoosuc River-Connecticut River; Ashuelot River-Connecticut River; Black River-Connecticut River; Contoocook River; Headwaters Connecticut River; Lower Androscoggin River; Merrimack River; Millers River; Nashua River; New England; Pemigewasset River; Piscataqua-Salmon Falls; Saco River; Upper Androscoggin River; Waits River-Connecticut River; West River-Connecticut River; Winnipesaukee River
NJ1905202312Crosswicks-Neshaminy; Great Egg Harbor; Hackensack-Passaic; Lower Delaware; Lower Hudson; Mid-Atlantic Region; Middle Delaware-Mongaup-Brodhead; Middle Delaware-Musconetcong; Mullica-Toms; Raritan; Rondout; Sandy Hook-Staten Island
NM1800202017Conejos; Jemez; Middle San Juan; Mimbres; Pecos Headwaters; Rio Chama; Rio Grande-Albuquerque; Rio Hondo; San Francisco; Tularosa Valley; Upper Canadian; Upper Gila; Upper Gila-Mangas; Upper Pecos; Upper Rio Grande; Upper San Juan; Upper San Juan
NY1883202258Ausable River; Black; Bronx; Buffalo-Eighteenmile; Cattaraugus; Chateaugay-English; Chaumont-Perch; Chautauqua-Conneaut; Chemung; Chenango; Conewango; East Branch Delaware; French; Grass; Hackensack-Passaic; Headwaters St. Lawrence River; Housatonic; Hudson-Hoosic; Hudson-Wappinger; Indian; Irondequoit-Ninemile; Lake Champlain; Lake Erie; Lake Ontario; Long Island Sound; Lower Genesee; Lower Hudson; Mettawee River; Middle Delaware-Mongaup-Brodhead; Middle Hudson; Mohawk; Niagara River; Northern Long Island; Oak Orchard-Twelvemile; Oneida; Oswegatchie; Oswego; Owego-Wappasening; Raisin River-St. Lawrence River; Raquette; Rondout; Sacandaga; Salmon; Salmon-Sandy; Sandy Hook-Staten Island; Saranac River; Saugatuck; Schoharie; Seneca; Southern Long Island; St. Regis; Tioga; Upper Allegheny; Upper Delaware; Upper Genesee; Upper Hudson; Upper Susquehanna; Upper Susquehanna
NC1961202320French Broad-Holston; Hiwassee; Lower Little Tennessee; Nolichucky; Pigeon; Roanoke; Seneca; South Fork Catawba; Tuckasegee; Tugaloo; Upper Broad; Upper Catawba; Upper Dan; Upper French Broad; Upper Little Tennessee; Upper New; Upper Pee Dee; Upper Tennessee; Upper Yadkin; Watauga, North Carolina, Tennessee
ND198419972Painted Woods-Square Butte; Red
OH1925202110Ashtabula-Chagrin; Hocking; Lake Erie; Little Miami; Lower Great Miami, Indiana, Ohio; Mohican; Sandusky; Upper Great Miami, Indiana, Ohio; Upper Scioto; Walhonding
OK195019975Arkansas-White-Red Region; Illinois; Lower Canadian-Walnut; Lower Cimarron-Skeleton; Mountain Fork
OR1935200915Clackamas; Deschutes; Klamath; Little Deschutes; Lower Willamette; Middle Willamette; North Umpqua; Pacific Northwest; Pacific Northwest Region; Sprague; Upper Deschutes; Upper John Day; Upper Malheur; Upper Rogue; Williamson
PA1886202353Allegheny; Bald Eagle; Beaver; Brandywine-Christina; Cacapon-Town; Chautauqua-Conneaut; Cheat; Chemung; Chester-Sassafras; Clarion; Conemaugh; Conewango; Connoquenessing; Conococheague-Opequon; Crosswicks-Neshaminy; French; Kiskiminetas; Lackawaxen; Lake Erie; Lehigh; Lower Allegheny; Lower Delaware; Lower Juniata; Lower Monongahela; Lower Susquehanna; Lower Susquehanna-Penns; Lower Susquehanna-Swatara; Lower West Branch Susquehanna; Mahoning; Middle Allegheny-Redbank; Middle Allegheny-Tionesta; Middle Delaware-Mongaup-Brodhead; Middle Delaware-Musconetcong; Middle West Branch Susquehanna; Monocacy; North Branch Potomac; Pine; Raystown; Schuylkill; Shenango; Sinnemahoning; Tioga; Upper Allegheny; Upper Delaware; Upper Genesee; Upper Juniata; Upper Ohio; Upper Ohio-Wheeling; Upper Susquehanna; Upper Susquehanna-Lackawanna; Upper Susquehanna-Tunkhannock; Upper West Branch Susquehanna; Youghiogheny
PR193419341Eastern Puerto Rico
RI198020232New England Region; Pawcatuck River
SC197120218Cooper; Saluda; Santee; Santee; Seneca; Tugaloo; Upper Broad; Upper Savannah
SD1930200214Cheyenne; Fort Randall Reservoir; Lewis and Clark Lake; Little White; Lower Belle Fourche; Lower Lake Oahe; Middle Cheyenne-Elk; Middle Cheyenne-Spring; Missouri Region; Rapid; Redwater; South Fork Grand; Upper Lake Oahe; Upper Moreau
TN1939202321Caney; Conasauga; French Broad-Holston; Hiwassee; Holston; Lower Clinch; Lower Cumberland-Old Hickory Lake; Lower Little Tennessee; Nolichucky; Obey; Ocoee; South Fork Cumberland; South Fork Holston; Upper Clinch, Tennessee, Virginia; Upper Cumberland-Cordell Hull Reservoir; Upper Cumberland-Lake Cumberland; Upper Elk; Upper French Broad; Upper Tennessee; Watauga, North Carolina, Tennessee; Watts Bar Lake
TX197520173Middle Canadian-Spring; Middle Guadalupe; Tule
UT1880202429Beaver Bottoms-Upper Beaver; Colorado Headwaters-Plateau; Duchesne; East Fork Sevier; Escalante; Fremont; Jordan; Little Bear-Logan; Lower Bear-Malad; Lower Green; Lower Green-Diamond; Lower Lake Powell; Lower Sevier; Lower Weber; Lower White; Middle Sevier; Price; Provo; San Rafael; Spanish Fork; Strawberry; Upper Colorado-Dirty Devil; Upper Colorado-Kane Springs; Upper Green-Flaming Gorge Reservoir; Upper Lake Powell; Upper Sevier; Upper Virgin; Upper Weber; Utah Lake
VT1975202017Ammonoosuc River-Connecticut River; Black River-Connecticut River; Deerfield River; Headwaters Connecticut River; Hudson-Hoosic; Lake Champlain; Lamoille River; Mettawee River; Missiquoi River; Otter Creek; Passumpsic River; Richelieu; St. Francois River; Waits River-Connecticut River; West River-Connecticut River; White River; Winooski River
VA1893202426Conococheague-Opequon; James; Kanawha; Lower Potomac; Maury; Middle James-Buffalo; Middle New; Middle Potomac-Catoctin; Middle Roanoke; North Fork Holston; North Fork Shenandoah; Potomac; Powell; Rapidan-Upper Rappahannock; Rivanna; Roanoke; South Branch Potomac; South Fork Holston; South Fork Shenandoah; Upper Clinch, Tennessee, Virginia; Upper Dan; Upper James; Upper Levisa; Upper New; Upper Roanoke; Upper Yadkin
WA1935201826Banks Lake; Chief Joseph; Colville; Deschutes; Franklin D. Roosevelt Lake; Hangman; Kettle; Lake Washington; Lewis; Lower Columbia-Clatskanie; Lower Crab; Lower Snake-Tucannon; Lower Spokane; Middle Columbia-Hood; Naches; Nisqually; Pacific Northwest Region; Pend Oreille; Puget Sound; Rock; Strait of Georgia; Upper Crab; Upper Skagit; Upper Spokane; Walla Walla; Yakima
WV1980202317Big Sandy; Cheat; Elk; Gauley; Greenbrier; Guyandotte; Little Kanawha; Little Muskingum-Middle Island; Lower New; Middle New; Monongahela; North Branch Potomac; Potomac; South Branch Potomac; Tygart Valley; Upper James; Upper Kanawha
WI1900202251Apple-Plum; Bad-Montreal; Baraboo; Beartrap-Nemadji; Black; Black-Presque Isle; Brule; Buffalo-Whitewater; Castle Rock; Coon-Yellow; Door-Kewaunee; Duck-Pensaukee; Eau Claire; Flambeau; Grant-Little Maquoketa; Jump; Kickapoo; La Crosse-Pine; Lake Dubay; Lake Michigan; Lake Superior; Lake Winnebago; Lower Chippewa; Lower Fox; Lower St. Croix; Lower Wisconsin; Manitowoc-Sheboygan; Menominee; Middle Rock; Milwaukee; Namekagon; Oconto; Ontonagon; Pecatonica; Peshtigo; Pike-Root; Red Cedar; Rush-Vermillion; South Fork Flambeau; St. Croix; St. Louis; Sugar; Trempealeau; Upper Chippewa; Upper Fox; Upper Fox; Upper Rock; Upper St. Croix; Upper Wisconsin; Wisconsin; Wolf
WY1880202356Beaver; Big Horn; Big Horn Lake; Big Sandy; Bitter; Blacks Fork; Cache La Poudre; Central Bear; Clarks Fork Yellowstone; Clear; Crazy Woman; Crow; Glendo Reservoir; Great Divide Closed Basin; Greybull; Greys-Hoback; Gros Ventre; Horse; Little Bighorn; Little Wind; Lower Henrys; Lower Laramie; Lower Wind; Madison; Medicine Bow; Middle Fork Powder; Middle North Platte-Casper; Middle North Platte-Scotts Bluff; Missouri Headwaters; Muddy; New Fork; North Fork Shoshone; North Platte; Nowood; Pathfinder-Seminoe Reservoirs; Popo Agie; Redwater; Salt; Shoshone; Snake Headwaters; South Fork Shoshone; Sweetwater; Upper Bear; Upper Belle Fourche; Upper Bighorn; Upper Green; Upper Green; Upper Green-Flaming Gorge Reservoir; Upper Green-Slate; Upper Laramie; Upper North Platte; Upper Powder; Upper Tongue; Upper Wind; Upper Yellowstone; Yellowstone Headwaters

Table last updated 6/13/2024

† Populations may not be currently present.

* HUCs are not listed for states where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Ecology: Brown Trout are a cold-water species that can inhabit streams, rivers, and lakes in both fresh and brackish waters. It lives in a wide range of depths and velocities, but competes best with other salmonids in faster flowing waters (Armstrong et al. 2003). Some individuals from freshwater tributaries can opt to migrate into the ocean to feed in estuaries and coastal waters, after which they can return to spawn. These individuals are referred to as ‘Sea Trout’ and typically take on a silver coloration.  Brown Trout are commonly found in waters 5–25?, but are known to tolerate water temperatures 0–30? (Elliot and Elliot 2010). The range of Brown Trout in the U.S. is believed to be threatened by warming waters as a symptom of climate change. However, there is evidence that Brown Trout possess mechanisms that allow them to adapt to higher temperatures by increasing its trophic position and increasing energy transfer efficiencies (O’Gorman et al. 2016). Despite this, swimming performance was documented to decrease above 22? (Nudds et al. 2020). Another symptom of climate change is the reduction in ice cover. For Brown Trout, ice cover is associated with increased activity level and reduced stress (relative to no ice cover), the loss of which may negatively impact energy budgets and production (Watz et al. 2015).

This species is a sight-feeder (Greer et al. 2015) with a diverse diet that spans a wide trophic niche. Brown Trout consume benthic invertebrates (Johnson et al. 2017), crustaceans, fish, and can be cannibalistic (Anderson et al. 2016; French et al. 2016; Musseau et al. 2017). Its wide trophic niche is thought to provide greater resilience to changes in the forge base relative to other salmonids and helps prevent the development of a Thiamine Deficiency Complex (TDC) (Futia and Rinchard 2019; Kornis et al. 2020; Leonhardt et al. 2020). Brown Trout are consumed by other piscivorous fish, including Pike, Charr, and Walleye and are a popular fish amongst anglers (Hesthagen et al. 2015; Krueger et al. 2016).

Landlocked populations of Brown Trout mature after 2-4 years, spawn in late fall and early winter in streams and tributaries, and can spawn across multiple years.  Females dig out a nest in gravel beds and males defend the nest until spawning is complete (Greely 1932). Fecundity ranges on average from 200–1000 eggs per female and increases with fish size (Taube 1972). Brown Trout usually live for 5–6 years, but can extend their lifespan to around 12 years by switching to a primarily fish based diet (Behnke 2002).

Means of Introduction: The Brown Trout was first imported to the United States in 1883 from Germany and stocked in the Pere Marquette River, Michigan, by the U.S. Fish Commission (Mather 1889; Courtenay et al. 1984). Since then, the species has been stocked in virtually every state. MacCrimmon et al. (1970) gave dates of first stocking in each state. In most regions the species was first stocked in the late 1800s or early 1900s.

Status: Natural reproduction is low or nonexistent in most states, as such, many states maintain Brown Trout populations by periodic stocking. Rinne (1995) listed this species as established in Arizona, but the species may not be reproducing in open waters (lakes and reservoirs); Rinne apparently used the term 'established' for species that maintain long-term populations through continual or periodic stockings. Courtenay et al. (1984) indicated that introductions failed to establish populations in Florida, Kansas, Ohio, and Oklahoma.

Great Lakes: Widespread, with populations reproducing and overwintering at self-sustaining levels in all five Great Lakes.

Impact of Introduction: Brown Trout have been implicated in reducing native fish populations (including other salmonids) through predation, displacement, and food competition (Taylor et al. 1984). Many studies have been conducted looking at the effects of Brown Trout on Brook Trout Salvelinus fontinalis including Nyman (1970), Fausch and White (1981), Waters (1983), Fausch and White (1986), and DeWald and Wilzbach (1992), to name a few. Taylor et al. (1984) list a number of papers citing the effects of Brown Trout on native fishes. Fausch and White (1981) stated adult Brown Trout displaced adult native Brook Trout from the best habitats in a Michigan stream, and in the northeast in general. Brook Trout are also more susceptible to angling and predation than Brown Trout. Conversely, juvenile Brook Trout are dominant over juvenile Brown Trout of the same size in an artificial stream (Fausch and White 1986). The competitive advantage of the two species may change with size, age, temperature, stream size, or environmental adaptations of different populations (Fausch and White 1986). Wagner et al. (2013) used two-species occupancy models to examine the distribution of Brook and Brown Trout in Pennsylvania streams, and found that predicted occurrence of Brook Trout was lower in the presence of Brown Trout across a wide range of landscape habitat characteristics. McKenna et al. (2013) used  artificial neural network models, ordination, and simulations and found that stocking intensity of Brown Trout into Brook Trout habitat was a major factor in Brook Trout abundance, more so than habitat differences or interspecific interactions. Brown trout have had negative effects on other species of trout and other native fishes throughout the US. For example, Houde et al. (2015a) found that juvenile Brown Trout reduced the survival and growth of juvenile Atlantic Salmon (Salmo salar) from three populations in artificial stream trials. In California, competition and predation from Brown Trout may have contributed to the decline of the Dolly Varden (S. malma) in the McCloud River (Moyle 1976), and of the Golden Trout (Oncorhynchus aguabonita) in the Kern River (Krueger and May 1991; Courtenay and Williams 1992). Also, Brown Trout have commonly replaced Cutthroat Trout (O. clarkii) in large rivers (Behnke 1992). McAffee (1966) specifically lists Lahontan cutthroats (O. c. henshawi) as being replaced by Brown Trout. Introduced Brown Trout, and other trout species, were likely responsible for the near-extinction of Lahontan cutthroat in Lake Tahoe in the 1940s (McAffee 1966). Although it rarely occurs, Brown Trout is one of the few foreign species able to hybridize with natives (e.g., S. fontinalis) (Brown 1966; Taylor et al. 1984).

Brown Trout have also negatively affected fish species. For example, Brown Trout may have depleted the Modoc Sucker (Catostomus microps), an endangered species, in Rush Creek, Modoc County (Moyle and Marciochi 1975). Because of their predatory nature, Brown Trout were introduced into Flaming Gorge Reservoir to reduce populations of the Utah Chub (Gila atraria) (Teuscher and Luecke 1996).  Competition with and predation by nonnative species (i.e., Catostomus sp., Creek Chub (Semotilus atromaculatus), Redside Shiner (Richardsonius balteatus), Burbot (Lota lota), Brown Trout (Salmo trutta), and Lake Trout (Salvelinus namaycush)) limit populations of the rare Bluehead Sucker (Catostomus discobolus) (Wyoming Game and Fish Department 2010). Brown Trout occupy similar habitat types as, and predate upon, Roundtail Chub (Gila robusta) (a species of conservation concern) in Wyoming lakes (Laske et al. 2012). Nonnative predators, including Brown Trout, have been shown to reduce the abundance and diversity of native prey species in several Pacific Northwest rivers (Hughes and Herlihy 2012).

Remarks: The state of California has attempted to eradicate Brown Trout in some areas in order to preserve native Golden Trout O. aguabonita (Taylor et al. 1984; Moyle, personal communication). Tyus et al. (1982) mapped the distribution of the Brown Trout in the upper Colorado basin. MacCrimmon and Marshall (1968) and MacCrimmon et al. (1970) summarized information on worldwide distribution and introductions. 

References: (click for full references)

Al-Chokhachy, R., and A.J. Sepulveda. 2019. Impacts of nonnative Brown Trout on Yellowstone Cutthroat Trout in a tributary stream. North American Journal of Fisheries Management 39(1):17-28. https://afspubs.onlinelibrary.wiley.com/doi/10.1002/nafm.10244.

Álvarez, D., and E. Garcia-Vasquez. 2011. Maintenance of asymmetric hybridization between Atlantic salmon (Salmo salar) and Brown Trout (Salmo trutta) via postzygotic barriers and paternal effects. Canadian Journal of Fisheries and Aquatic Sciences 68(4):593-602.

Anderson, A.M., E. Mittag, B. Middleton, B. Vondracek, and L.C. Ferrington. 2016. Winter diets of brown trout populations in southeastern Minnesota and the significance of winter-emerging invertebrates. Transactions of the American Fisheries Society 145(1):206–220. https://doi.org/10.1080/00028487.2015.1111258.

Armstrong, J.D., P.S. Kemp, G.J.A. Kennedy, M. Ladle, and N.J. Milner. 2003. Habitat requirements of Atlantic salmon and brown trout in rivers and streams. Fisheries Research 62(2):143–170. https://doi.org/10.1016/s0165-7836(02)00160-1.

Behnke, R.J. 1992. Native trout of western North America. American Fisheries Society Monograph 6. American Fisheries Society, Bethesda, MD.

Behnke, R.J. 2002. Trout and Salmon of North America. The Free Press, NY.

Belk, M.C., E.J. Billman, C. Ellsworth, and B.R. McMillan. 2016. Does habitat restoration increase coexistence of native stream fishes with introduced brown trout: a case study on the middle Provo River, Utah, USA. Water 8(4):121. https://doi.org/10.3390/w8040121.

Bence, J.R., and K.D. Smith. 1999. An overview of recreational fisheries of the Great Lakes. Pages 259-306 in Taylor, W.W., and C.P. Ferreri, eds. Great Lakes fisheries policy and management: a binational perspective. Michigan State University Press. East Lansing, MI.

Boogaard, M.A., T.D. Bills, and D.A. Johnson. 2003. Acute toxicity of TFM and a TFM/niclosamide mixture to selected species of fish, including lake sturgeon (Acipenser fulvescens) and Mudpuppies (Necturus maculosus), in Laboratory and Field Exposures. Journal of Great Lakes Research 29(Supplement 1):529-541.

Brown, C.J.D. 1966. Natural hybrids of Salmo trutta and Salvelinus fontinalis. Copeia 1966(3):600-601.

Brown, C.J.D., and A.C. Fox. 1966. Mosquito fish (Gambusia affinis) in a Montana pond. Copeia 1966(3):614-616.

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FishBase Summary

Author: Fuller, P., J. Larson, A. Fusaro, T.H. Makled, M. Neilson, and A. Bartos

Revision Date: 4/8/2022

Peer Review Date: 4/8/2022

Citation Information:
Fuller, P., J. Larson, A. Fusaro, T.H. Makled, M. Neilson, and A. Bartos, 2024, Salmo trutta Linnaeus, 1758: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=931, Revision Date: 4/8/2022, Peer Review Date: 4/8/2022, Access Date: 6/13/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/13/2024].

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For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.