brown trout

(Salmo trutta)

Conservation Status

IUCN Red List

LC - Least Concern

NatureServe

NNA - Not applicable

SNA - Not applicable

Minnesota

not listed

Invasive/Noxious Status

Brown trout preys on other trout species, and it competes with them for the same resources. It is listed as an invasive species in Massachusetts, Minnesota, and Wisconsin.

 
brown trout
Photo by Greg Watson
 
Description

Brown trout is an exotic, invasive fish. It is native to Europe and North Africa. It was first introduced in New York and separately in Newfoundland Canada in 1883. Since then, it has been introduced several times into several locations in North America. It now occurs throughout the United States and to a lesser extent across southern Canada. It is common in Minnesota.

Brown trout is a highly adaptable fish found in streams, rivers, and lakes. Adults prefer deep, moderate to slow streams, but it spawns in shallow, fast-moving streams and that is where the juveniles are found. It is a hardy fish that can withstand warmer and cloudier water than rainbow trout. Trout streams in southern Minnesota have mostly brown trout, and trout streams in northern Minnesota have mostly rainbow trout.

The size of an adult fish depends on both its age and its habitat. Stream brown trout are usually 10 to 15 (25 to 38 cm) long and weigh 3½ to 5½ lbs. (1.6 to 2.5 kg), though they can get much bigger. Lake brown trout are much bigger. The Minnesota state record brown trout is 16¾ lbs. (7.56 kg).

The head is small and pointed. The mouth is large, and it has well developed teeth all along both jaws. The upper jaw (maxilla) extends beyond the eye. The lower jaw is whitish, and it has no gray or black markings.

In the gills, there are usually 10 curved bones (branchiostegal rays) supporting the gill membranes.

The body is long, slender, and tapered. The row of pores that runs from the gills to the tail (lateral line) is faint but visible. The scales are small. There are more than 20 rows of scales above the lateral line, and 120 to 130 scales on the lateral line. The ground color is brown or yellowish brown. The upper body is densely covered with small dark spots surrounded by broad pale halos. The largest dark spot is smaller than the diameter of the eye. There are numerous dark spots below the lateral line. The lower body has several red spots that are also surrounded by pale halos. There are 3 or 4 dorsal spines and 3 or 4 anal spines. The adipose fin has a red margin. The anal fin usually has 10 to 12 rays. The tail (caudal) fin is symmetrical, with two lobes of equal proportion. It either has no black spots, or there are poorly developed black spots only on the upper lobe.

 

Size

 

 

Similar Species

 
Habitat

 

Ecology

Behavior

 

 

Lifespan

 

 

Life Cycle

 

 

Food

 

Distribution

Distribution Map

 

Sources

4, 24, 29, 30, 76.

Nonindigenous Aquatic Species (NAS) information resource for the United States Geological Survey

12/12/2024    
     

Occurrence

Locally common

Taxonomy

Superclass

Actinopterygii (ray-finned fishes)

Class

Actinopteri

Subclass

Neopterygii

Infraclass

Teleostei (teleost fishes)

Clade

Osteoglossocephalai

no rank

Clupeocephala

Cohort

Euteleostei (= Euteleosteomorpha)

Superorder

Protacanthopterygii

Order

Salmoniformes (salmons, pikes, and mudminnows)

Suborder

Salmonoidae (salmons, trouts, and whitefishes)

Family

Salmonidae (salmons, trouts, and whitefishes)

Subfamily

Salmoninae (salmons and trouts)

Genus

Salmo (Atlantic salmons and trouts)

   

Subordinate Taxa

Many subspecies and varieties of Salmo trutta have been described. Brown trout has been introduced into several locations in North America from several locations in Europe. Those introductions included sea forms, lake forms, and river forms. It is believed by some that the imported subspecies have cross-bred, producing what has become a single North American subspecies Salmo trutta ssp. trutta.

Some sources recognize one subspecies and up to 19 varieties (GBIF). Some sources recognize four subspecies (NCBI and iNaturalist). Some sources classify three of those varieties as morphs (Wikipedia). Most sources do not recognize any infraspecific taxa in North America (ITIS, NatureServe, Catalog of Life, and Discover Life).

   

Aral Sea trout (Salmo trutta ssp. aralensis)

lake brown trout (Salmo trutta ssp. lacustris)

river brown trout (Salmo trutta ssp. fario)

sea brown trout (Salmo trutta ssp. trutta)

   

Synonyms

Fario argenteus

Fario lacustris

Fario trutta

Salar ausonii

Salar ausonii var. parcepunctata

Salar ausonii var. semipunctata

Salar bailloni

Salar gaimardi

Salar spectabilis

Salmo abanticus

Salmo albus

Salmo albus

Salmo brachypoma

Salmo caecifer

Salmo cambricus

Salmo cornubiensis

Salmo cumberland

Salmo eriox

Salmo estuarius

Salmo fario

Salmo fario loensis

Salmo fario major

Salmo fario var. forestensis

Salmo faris var. forestensis

Salmo gadoides

Salmo gallivensis

Salmo illanca

Salmo islayensis

Salmo lacustris

Salmo lacustris rhenana

Salmo lacustris romanovi

Salmo lacustris septentrionalis

Salmo lemanus

Salmo levenensis

Salmo mistops

Salmo montana

Salmo orcadensis

Salmo orientalis

Salmo oxianus

Salmo phinoc

Salmo polyosteus

Salmo rappii

Salmo saxatilis

Salmo spurius

Salmo stroemii

Salmo sylvaticus

Salmo taurinus

Salmo trutta aralensis

Salmo trutta ciscaucasicus

Salmo trutta ezenami

Salmo trutta fario

Salmo trutta lacustris

Salmo trutta oxianus

Salmo trutta trutta

Salmo truttula

Salmo venernensis

Trutta fario

Trutta fluviatilis

Trutta lacustris

Trutta marina

Trutta salmanata

Trutta salmonata

Trutta trutta

Trutta variabilis

 

Common Names

brown trout

 

 

 

 

 

 

 

 

 

Glossary

Lateral line

In fish: A faint row of pores along a fish’s body from the gills to the tail. It allows the fish to detect movement, vibrations, and pressure gradients in the water around them.

 

Maxilla

The upper jaw of a fish formed by two bones and having teeth attached to it.

 

 

 

 

 

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Greg Watson

brown trout
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slideshow

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Other Videos

Ecosystem in a modified river - Wild Salmo trutta (Brown trout) - Natural habitat ᴴᴰ
Carlos Díez

About

Jan 24, 2017

Location: Andorra

Filmed in January, at the beginning of the spawning season of trout. The spawning behaviour of brown trout is similar to that of the closely related Atlantic salmon.

Mediterranean native brown trout in the Pyrenees.

Brown trout (Salmo trutta) ⁴ᵏ ᵁˡᵗʳᵃ ᴴᴰ
4K Ultra HD Wildlife & Nature

About

Dec 31, 2017

The native range of brown trout extends from northern Norway and White Sea tributaries in Russia in the Arctic Ocean to the Atlas Mountains in North Africa. The western limit of their native range is Iceland in the north Atlantic, while the eastern limit is in Aral Sea tributaries in Afghanistan and Pakistan.

The fish is not considered to be endangered, although, in some cases, individual stocks are under various degrees of stress mainly through habitat degradation, overfishing, and artificial propagation leading to introgression. Increased frequency of excessively warm water temperatures in high summer causes a reduction in dissolved oxygen levels which can cause "summer kills" of local populations if temperatures remain high for sufficient duration and deeper/cooler or fast, turbulent more oxygenated water is not accessible to the fish. This phenomenon can be further exacerbated by eutrophication of rivers due to pollution—often from the use of agricultural fertilizers within the drainage basin.

Overfishing is a problem where anglers fail to identify and return mature female fish into the lake or stream. Each large female removed can result in thousands fewer eggs released back into the system when the remaining fish spawn.

Another threat is other introduced organisms. For example, in Canada's Bow River, a non-native alga Didymosphenia geminata—common name rock snot (due to appearance)—has resulted in reduced circulation of water amongst the substrate of the river bed in affected areas. This, in turn, can greatly reduce the number of trout eggs which survive to hatch.

Red List Category & Criteria: Least Concern

Current Population Trend: Unknown

English - Brown Trout, Sea Trout

Spanish - Trucha común, Trucha marrón, Reo

Sea trout in the UK and Ireland have many regional names, including sewin (Wales), finnock (Scotland), peal (West Country), mort (North West England), and white trout (Ireland).

Underwater footage of Brown Trout spawning (Salmo trutta). Tření Pstruha obecného potočního.
CzechUnderwater

About

Feb 26, 2023

Underwater footage of spawning Brown Trout (Salmo trutta morpha fario).

 

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Greg Watson
9/6/2024

Location: Beaver Creek Valley State Park

brown trout
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Created: 12/12/2024

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