Salmo trutta

Salmo trutta is a common trout known by two different common names reflecting the alternative ecological strategies and associated morphological characteristics of this species. The freshwater morphs (Salmo trutta morpha fario and S. trutta morpha lacustris) are known as brown trout. Sea trout is the anadromous morph which migrates between the ocean, where it spends most of its life, and freshwater spawning grounds. The two morphs, which often share the same breeding grounds (sympatric distribution), have in the past been classified as distinct species. The morphs do interbreed, but the extent of reproductive isolation between them varies by location and some studies have found genetic differentiation between morphs inhabiting the same territory.

Although native to Europe, northern Africa and western Asia, S. trutta has been widely introduced for aquaculture and recreational fishing purposes and is found in streams, lakes, and coastal areas throughout the world. Brown trout commonly mature at 13-16 inches long (often longer in large streams); sea-run morphs are larger and can be found up to 30 pounds and 3 feet long. An aggressive species, S. trutta has been responsible for declines in native fish populations, for example in the Great Lakes, where they displaced Arctic greyling (Thymallus arcticus) and in California, where they threaten native golden trout Oncorhynchus mykiss aguabonita and Dolly Varden (Salvelinus malma). This species was nominated as one of the world’s 100 worst invasive species by the Invasive Species Specialist Group (ISSG).

(CABI 2010;Charles et al 2005; Fuller, Larson and Fusaro 2012; Global Invasive Species Database, Invasive Species Specialist Group; Idema 1999; Wikipedia 2012)

Global Range: Native to Europe and western Asia. Introduced and established throughout much of U.S. and southern Canada; locally common.

Atlantic, North, White and Baltic Sea basins, from Spain to Chosha Bay (Russia). Present in Iceland and in northernmost rivers of Great Britain and Scandinavia. In Rhône drainage, native only to Lake Geneva basin, which it entered after last glaciation. Native to upper Danube and Volga drainages. Introduced throughout Europe, North and South America, southern and montane eastern Africa, Pakistan, India, Nepal, Japan, New Zealand and Australia.

Eastern North Atlantic, Baltic Sea, North Sea, Mediterranean Sea, Black Sea, Caspian Sea, Europe and western Asia, introduced widely elsewhere.

Brown trout are native to Europe. The species is found in Iceland and on the Northwest coast of Europe, along the Mediterranean and south to India. They have been introduced to appropriate streams all over the world.

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

Other Geographic Terms: cosmopolitan

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

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Adult browns are generally 13 to 16 inches (33-40.6 cm) in length, although old individuals can reach a much larger size. Their bodies are olive brown or green shading to a yellowish white on the belly. The sides of the fish have beautiful red spots surrounded by a pale halo.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Length: 103 cm

Habitat and Ecology

Systems

• Freshwater

The species can live in a higher temperature than most other trouts, and this is probably why they were introduced to North America. They are a succesful and aggressive species who are permanent residents in most of the regions where they have been released.

Habitat Regions: temperate ; freshwater

Aquatic Biomes: rivers and streams

Depth range based on 327 specimens in 2 taxa.
Water temperature and chemistry ranges based on 19 samples.

Environmental ranges
  Depth range (m): -9 - 92
  Temperature range (°C): 4.995 - 10.817
  Nitrate (umol/L): 1.687 - 6.728
  Salinity (PPS): 9.183 - 34.886
  Oxygen (ml/l): 2.247 - 7.708
  Phosphate (umol/l): 0.389 - 1.719
  Silicate (umol/l): 2.022 - 48.967

Graphical representation

Depth range (m): -9 - 92

Temperature range (°C): 4.995 - 10.817

Nitrate (umol/L): 1.687 - 6.728

Salinity (PPS): 9.183 - 34.886

Oxygen (ml/l): 2.247 - 7.708

Phosphate (umol/l): 0.389 - 1.719

Silicate (umol/l): 2.022 - 48.967
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Freshwater

Comments: Mostly in cold, medium to high gradient streams, but lake and sea-run populations also exist. Tends to occupy deeper, lower velocity, and warmer waters than other species of trout (Sublette et al. 1990). Does best where dissolved oxygen concentration is at least 9 ppm and, in small streams, where canopy shade is 50-75% at midday (Sublette et al. 1990). Some migratory populations spend first 2 years in river, 1-2 years in lake, then return to river to spawn at 3-4 years. Spawns in waters ranging from large streams to small spring- fed tributaries; in shallow gravelly headwaters, rocky lake margins, or sometimes over sand or hard clay if no gravel available. Spawns in natal stream. Fry occupy quiet waters along shorelines or in shelter of objects that deflect flows (Sublette et al. 1990).

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: No. No populations of this species make annual migrations of over 200 km.

Migrates between lakes and spawning streams or between sea and spawning streams in some areas (Scott and Crossman 1973).

Smaller brown trout feed primarily on insects. The most important insects vary with the season but the bulk of them are mayflies, caddisflies, midges or terrestrial insects. Browns in smaller streams are also dependent on food washed from the banks. Small browns select an area for feeding in a drift and do not move from it until a predator is introduced. This foraging site is characterized by a good view of the drift near refuge sites such as deep water or complex structure. Small browns never feed immediately upstream of a larger fish. Large browns' diets are more diverse than that of younger browns. Smaller trout account for 80% of the large brown's diet. The remaining diet consists of large aquatic insects such as Hexagania and Brown Drake (Ephemera simulans) mayflies and larger species of caddisflies (Trichoptera), crustaceans, snails, amphibians, and food washed from the bank. Also, the feeding habits of large browns is primarily nocturnal. They eat whatever is in the immediate area, preferably about 4 inches from the stream's floor in riffles, pools, or eddies. In contrast to young browns, large brown trout do not sit and wait for food, they hunt it actively.

Animal Foods: fish; insects; terrestrial non-insect arthropods; aquatic crustaceans; zooplankton

Primary Diet: carnivore (Piscivore , Insectivore )

Comments: Eats aquatic and terrestrial insects and their larvae, crustaceans (especially crayfish), molluscs, fishes, and other animals. In streams, young feed mainly on aquatic and terrestrial drift invertebrates; in lakes, they feed on zooplankton and benthic invertebrates (Sublette et al. 1990). Large adults feed on fishes, crayfish, and other benthic invertebrates.

In Great Britain and/or Ireland:
Animal / parasite / ectoparasite
Argulus foliaceus ectoparasitises skin of Salmo trutta

Animal / parasite / endoparasite
fluke of Crepidostomum faronis endoparasitises hind gut of Salmo trutta

Animal / parasite / endoparasite
fluke of Crepidostomum metoecus endoparasitises intestine of Salmo trutta

Animal / parasite / endoparasite
Cryptobia truttae endoparasitises blood of Salmo trutta

Animal / parasite / endoparasite
tapeworm of Cystidicola farionis endoparasitises swim bladder of Salmo trutta

Animal / parasite
tapeworm of Cystidicoloides tenuissima parasitises Salmo trutta

Animal / parasite / endoparasite
Diphyllobothrium dendriticum endoparasitises body cavity of Salmo trutta

Animal / parasite / endoparasite
metacaria (diplostomula) of Diplostomum gasterostei endoparasitises eye (humour) of Salmo trutta

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

Animal / parasite / endoparasite
Echinorhynchus truttae endoparasitises Salmo trutta

Animal / parasite / endoparasite
tapeworm of Eubothrium crassum endoparasitises intestine of Salmo trutta

Animal / parasite / endoparasite
Neoechinorhynchus rutili endoparasitises intestine of Salmo trutta

Animal / pathogen
colony of Saprolegnia parasitica infects epidermis of Salmo trutta

Animal / parasite / endoparasite
metacaria (diplostomula) of Tyrodelphys clavata endoparasitises vitreous humour of Salmo trutta

Salmo trutta (Salmo trutta (N=3)) is prey of:
Lutra lutra
Phalacrocorax carbo
Ardea cinerea
Larus argentatus

Based on studies in:
Scotland (Estuarine)

This list may not be complete but is based on published studies.

Salmo trutta (Salmo trutta (N=3)) preys on:
Insecta
zoobenthos
Cyclops
Simulium
Crangon crangon
Nereis diversicolor
Copepoda
Balanus balanoides
Neomysis integer
Corophium volutator
Gammarus
Jaera albifrons
Hydrobia ulvae
Lepomis macrochirus
Terrestrial invertebrates
Plant material
Costachorema xanthoptera
Deleatidium lilli
Megaleptoperla diminuta
Oeconesus
Oligochaeta
Paracalliope fluviatalus
Polyplectropus puerilis
Stenoperla prasinia
Zelandoperla agnetis
Paranephrops zealandicus
detritus
Amphipoda
Aoteapsyche
Aphrophila noevaezelandiae
Austrosimulium australense
Maoridiamesea
Naonella
Coloburiscus humeralis
Deleatidium
Hudsonema amabilis
Hydora nitida
Hydrobiosidae
Potamopyrgus antipodarum
Psilachorema bidens
Pycnocentrodes evecta
Zelandoperlinae
Archichauliodes diversus
Tanytarsini
Helicopsyche albescens
Hudsonema aliena
Scirtidae
Cricotopus II
Hydrobiosis parumbripennis
Hydrobiosis type Black Pronotum
Hydrobiosis type checkers
Nesameletus ornatus
Olinga feredayi
Pycnocentria
Pycnocentrodes
Zelandoperla
Zephlebia spectabilis
Austroclima jollyae
Diamesid Blond
Diamesid Brown Orange
Neocurupira hudsonii
Stenoperla cyrene
Terrestial invertebrates
Amelotopsis perscitus
Atalophlebioides cromwelli
Baraeoptera roria
Pirara
Polypedellum
Cricotopus I
Hydrobiosis
Oxyethira albiceps
Orthocladiinae
Eukiefferiella
Tanytarsini I
Hydraena orchymontia
Hydrobiosella
Paroxyethira eatoni/hintoni
Zelolessica cheira
Tanypodini
Olinga feredayii
Aoteapsyche raruraru
Austroperla cyrene
Hydrobiosella stenocerca
Hydrobiosis charadrea
Megaleptoperla grandis
Orchymontia
Paracalliope
Philorheithrus agilis
Polypedilum Type II
Pycnocentria evecta
Terrestrial invertebrate remains
Aoteapsyche colonica
Hydrobiosis frater
Naonella forsythii
Tanytarsus type blunt
Orthoclad Blue Black
Oligochaeta II
Podaena
Zelandoperla fenestrata

Based on studies in:
Austria, Vorderer Finstertaler Lake (Lake or pond)
England, River Cam (River)
Scotland (Estuarine)
New Zealand: Otago, Berwick, Meggatburn (River)
New Zealand: Otago, Blackrock, Lee catchment (River)
New Zealand: Otago, Broad, Lee catchment (River)
New Zealand: South Island, Canton Creek, Taieri River, Lee catchment (River)
New Zealand: Otago, Dempster's Stream, Taieri River, 3 O'Clock catchment (River)
New Zealand: Otago, German, Kye Burn catchment (River)
New Zealand: Otago, Kye Burn (River)
New Zealand: Otago, North Col, Silver catchment (River)
New Zealand: Otago, Sutton Stream, Taieri River, Sutton catchment (River)
New Zealand: Otago, Venlaw, Mimihau catchment (River)
New Zealand: Otago, Little Kye, Kye Burn catchment (River)

This list may not be complete but is based on published studies.

Preys on other species of trout and competes with them for food and space (Sublette et al. 1990).

Communication Channels: visual ; tactile ; chemical

Perception Channels: visual

Comments: Feeding most intense at twilight (Sublette et al. 1990).

Average lifespan
Status: wild: 11.0 years.

Average lifespan
Status: wild: 8.0 years.

Average lifespan
Status: captivity: 10.0 years.

Average lifespan
Status: wild: 18.0 years.

Maximum longevity: 38 years Observations: These animals normally do not live more than 6 years (Das 1994). In some cases, such as the ferox trout, animals may start preying other fishes and growing much faster, and end up living longer as well.

When brown trout spawn, the male and female are not monogamous. These trout mate every year, and they are not likely to have the same mate year after year. Occasionally, large males take over a bed already occupied by a smaller, less aggressive trout.

Mating System: polygynandrous (promiscuous)

Brown trout mature at about 3 or 4 years of age. They spawn in the fall from October into December. When they spawn, they head into shallow headwater brooks of the river. The female scoops out a hollow on a gravel "redd" where she can lay her eggs. As she releases the eggs on the redd, the male simultaneously releases milt to fertilize them. The pair continues this process until all of the female's eggs are spent. The female then covers the fertilized eggs with sand or gravel for protection. The eggs are then left to develop and hatch the following spring. Browns do not necessarily come back to the same gravel bed to spawn each year, but they come back to the same general area of the river.

Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

Average number of offspring: 8000.

Female brown trout invest nutrients in yolk for eggs, but do not provide any care after the eggs are laid. Male brown trout provide no investment in offspring after fertilization.

Parental Investment: pre-fertilization (Provisioning)

Spawns in fall or early winter. Eggs hatch in 1-2 months, depending on temperature. Sexually mature in 2nd or 3rd year (or up to 5th year). Typically spawns in more than one year.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 73
Specimens with Barcodes: 95
Species With Barcodes: 1

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

There are 27 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.

Download FASTA File

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
  (IUCN 2008)
• 1996
  Lower Risk/least concern

Brown trout are an abundant and widespread species, and so are not considered in need of special conservation efforts to preserve the species as a whole. Since they are a popular game fish, they are often protected by local fishing regulations.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Major Threats

Conservation Actions

When introduced outside their native range, brown trout compete with and prey upon native trout and other fish and amphibian species. Introduction of brown trout has been associated with declines in native brook trout in the eastern U.S. and frog species in the west. In some locations, brown trout may act as a prey base for parasitic sea lampreys (Petromyzon marinus). This may increase lamprey pressure on other native species. Introductions of brown trout may also bring fish diseases that can attack native species as well.

The main economic benefit of brown trout is the sport of fishing for the species. Many people pursue the sport fishing and some flyfish for browns. Many fisherman donate money to conservation groups to keep the sport alive. Also, browns make a delicious meal.

Positive Impacts: food ; ecotourism

Comments: Has been used in carcinogen testing (Metcalfe 1989).

Species Impact: Incompatible with native species such as cutthroat trout and Gila trout; protection of native species requires segregation of them from brown trout (Sublette et al. 1990).

Introduced populations in New Zealand exert strong top-down control of communty structure and ecosystem functioning via effects on individual behavior and population distribution and abundance (Townsend 2003).