The
brown trout and the
sea trout (
S. trutta morpha
trutta) are
fishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
of the same species.
They are distinguished chiefly by the fact that the brown trout is largely a
freshwaterFresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
fish, while the sea trout shows anadromous reproduction, migrating to the
oceanAn ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s for much of its life and returning to freshwater only to
spawnSpawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
. 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).
The
specificIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
epithet
trutta derives from the
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
trutta, meaning, literally, "trout".
The
lacustrineA lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
morph of brown trout is most usually
potamodromousMany types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
, migrating from lakes into rivers or streams to spawn, although there is some evidence of stocks that spawn on wind-swept shorelines of lakes.
S. trutta morpha
fario form stream-resident populations, typically in alpine streams but sometimes in larger rivers. There is evidence that anadromous and non-anadromous morphs coexisting in the same river can be genetically identical. In common usage, the name "brown trout" is often applied indiscriminately to the various morphs.
Range
The brown trout is normally considered to be native to
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and
AsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, but the natural distribution of the migratory forms may be, in fact, circumpolar. There are also landlocked populations far from the oceans, for example in
GreeceGreece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
and
EstoniaEstonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
.
Conservation status
The fish is not considered to be endangered although, in some cases, individual stocks are under various degrees of stress mainly through habitat degradation,
overharvestOverfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
and artificial propagation leading to
introgressionIntrogression, also known as introgressive hybridization, in genetics is the movement of a gene from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species...
. Increased frequency of excessively warm water temperatures in high summer, attributed to
global warmingGlobal warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
, causes a reduction in dissolved
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
levels which can cause 'summer kills' of local populations if temperatures remain high for sufficient duration and deeper/cooler or fast, turbulent more
oxygenatedEnvironmental oxygenation can be important to the sustainability of a particular ecosystem. Insufficient oxygen may occur in bodies of water such as ponds and rivers, tending to suppress the presence of aerobic organisms such as fish...
water is not accessible to the fish. This phenomenon can be further exacerbated by
eutrophicationEutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
of rivers due to
pollutionPollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
- often from the use of agricultural
fertilizerFertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s within the
drainage basinA drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
.
Overfishing is a problem where
anglerAngler may refer to:* A fisherman who uses the fishing technique of angling*Angler * The angler, Lophius piscatorius, a monkfish* More generally, any anglerfish in the order Lophiiformes* Angler , a Marvel Comics supervillain...
s 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
organismIn biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s. For example in
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
's
Bow RiverThe Bow River is a river in the Canadian province of Alberta. It is a tributary of the South Saskatchewan River, and is considered the headwater of the Nelson River....
, a non-native
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
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. Over time, this leads to reduction of the population of adult fish in the areas affected by the algae; forming a circle of decline. Rock Snot is believed to have spread accidentally on the soles of the footwear of visitors from areas where the algae is native. The wide variety of issues that adversely affect brown trout throughout its range, do not exclusively affect brown trout, but affect many or all species within a water body, thus altering the
ecosystemAn ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
in which the trout reside.
In small streams, brown trout are important predators of macro-
invertebrateAn invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, and declining brown trout populations in these specific areas would affect the entire aquatic
food webA food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
.
S. trutta morpha
fario prefers cold (though in comparison with other
trout, this species has a somewhat higher temperature preference of about 60-65 °F, or 15.5-18.3 °C), well-
oxygenatedEnvironmental oxygenation can be important to the sustainability of a particular ecosystem. Insufficient oxygen may occur in bodies of water such as ponds and rivers, tending to suppress the presence of aerobic organisms such as fish...
upland waters, especially large streams in mountainous areas.
Cover or structure is important to trout, and they are more likely to be found near submerged rocks, undercut banks, and overhanging vegetation. Structure provides protection from predators, bright sunlight and associated high water temperatures. Access to deep water for protection in winter freezes, or fast water for protection from low oxygen levels in summer are also ideal.
Characteristics
The brown trout is a medium-sized fish, growing to 20 kg or more in some localities although in many smaller rivers a mature weight of 1 kg (2 lb) or less is common.
The spawning behaviour of brown trout is similar to that of the closely related
Atlantic salmonThe Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
. A typical female produces about 2,000 eggs per kilogram (900 eggs per pound) of body weight at spawning.
On Sept. 11, 2009, a 41.45 lb (18.80 kg) Brown trout was caught by Tom Healy in the
ManisteeManistee may refer to a location in the United States:* Manistee, Michigan* Manistee County, Michigan** Manistee County-Blacker Airport* Manistee Township, Michigan...
river system in
MichiganMichigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
, setting a new state record and possibly, a new world record for Brown trout. As of late December 2009, the fish captured by Mr. Healy was confirmed by both the International Game Fish Association and the Fresh Water Fishing Hall of Fame, as the new all tackle world record for the species. This fish now supplants the former world record from the Little Red River in Arkansas.
Brown trout can live to ages of 20 years. But as with the
Atlantic salmonThe Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
, there is a high proportion of death of anadromous males after spawning and probably fewer than 20% of anadromous female kelts recover from spawning.
The migratory forms grow to significantly larger sizes for their age due to abundant forage fish in the waters they spend most of their lives. Brown trout are active both by day and by night and are opportunistic feeders. While in fresh water, the diet will frequently include invertebrates from the streambed, other fish,
frogFrogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s, mice, birds, and insects flying near the water's surface. The high dietary reliance upon insect larvae, pupae, nymphs and adults is what allows trout to be a favoured target for
fly fishingFly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...
. Sea trout are especially fished for at night using
wet fliesAn artificial fly or fly lure is a type of fishing lure, usually used in the sport of fly fishing . In general, artificial flies are the bait which fly fishers present to their target species of fish while fly fishing...
. Brown trout can be caught with lures such as spoons, spinners, jigs, plugs, plastic worm imitations, and live or dead baitfish.
Freshwater brown trout range in colour from largely silver with relatively few spots and a white belly, to the more well known brassy brown cast fading to creamy white on the fish's belly, with medium-sized spots surrounded by lighter haloes. The more silver forms can be mistaken for rainbow trout. Regional variants include the so-called "
Loch LevenLoch Leven is a fresh water loch in Perth and Kinross council area, central Scotland.Roughly triangular, the loch is about 6 km at its longest. The burgh of Kinross lies at its western end. Loch Leven Castle lies on an island a short way offshore...
" trout, distinguished by larger fins, a slimmer body, and heavy black spotting, but lacking red spots. The continental European strain features a lighter golden cast with some red spotting and fewer dark spots. It is important to remember that both strains can show considerable individual variation from this general description. Early stocking efforts in the United States used fish taken from
ScotlandScotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
and
GermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. The Loch Leven strain is more often found in the western United States, while the "German brown" is found more toward the Midwest and East.
Brown trout rarely form hybrids, almost invariably infertile, with other species. One such example is the
tiger troutThe tiger trout is a sterile, intergeneric hybrid of the brown trout and the brook trout . The name derives from the pronounced vermiculations, evoking the stripes of a tiger. It is a rare phenomenon in the wild, with the brook trout having 84 chromosomes and the brown trout 80...
, a hybrid with the
brook troutThe brook trout, Salvelinus fontinalis, is a species of fish in the salmon family of order Salmoniformes. In many parts of its range, it is known as the speckled trout or squaretail. A potamodromous population in Lake Superior are known as coaster trout or, simply, as coasters...
.
Diet
Young brown trout feed on insects and other invertebrates such as shrimp, flies, caddis, stonefly, mayfly, etc. Both larvae and adults are taken and the fish will eat whatever local insect life is abundant at the time. Larger fish are active predators of fish including young brown trout,
suckersCatostomidae is the sucker family of the order Cypriniformes. There are 80 species in this family of freshwater fishes. Catostomidae are found in North America, east central China, and eastern Siberia...
,
sculpinA Sculpin is a fish that belongs to the order Scorpaeniformes, suborder Cottoidei and superfamily Cottoidea, that contains 11 families, 149 genera, and 756 species...
s,
shadThe shads or river herrings comprise the genus Alosa, fish related to herring in the family Clupeidae. They are distinct from others in that family by having a deeper body and spawning in rivers. The several species frequent different areas on both sides of the Atlantic Ocean, Mediterranean Sea....
,
whitefishThe freshwater whitefish are fish of the subfamily Coregoninae in the salmon family Salmonidae. Along with the freshwater whitefish, the Salmonidae includes the freshwater and anadromous trout and salmon species as well as graylings...
and
rainbow troutThe rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....
. Larger brown trout will also feed on small terrestrial animals that fall into the water such as baby birds falling from overhanging nests, or even swimming mice/voles. Brown trout sometimes do not actively feed until the late afternoon or early evening but when the weather is cool they will feed during the day as well. The largest browns feed under cover of darkness. Brown trout can be caught with artificial flies, jigs, plastic worm imitations, spinners and other
luresA fishing lure is an object attached to the end of a fishing line which is designed to resemble and move like the prey of a fish. The purpose of the lure is to use movement, vibration, and colour to catch the fish's attention so it bites the hook...
.
Stocking, farming and non-native brown trout
The species has been widely
introducedAn introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
for purposes of sport into
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
,
South AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
,
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
and many other countries including
BhutanBhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
where they are the focus of a specialised fly fishery. First planting in the United States occurred April 11, 1884 into the Baldwin River, one mile east of Baldwin, MI. Brown trout have had serious negative impacts on
uplandIn studies of the ecology of freshwater rivers, habitats are classified as upland and lowland.-Definitions:Upland habitats are cold, clear, rocky, fast flowing rivers in mountainous areas; lowland habitats are warm, slow flowing rivers found in relatively flat lowland areas, with water that is...
native fish species in some of the countries where they have been introduced, particularly Australia. Because of the trout's importance as a food and game fish, it has been
artificially propagatedA hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons A hatchery is a...
and stocked in many places in its range, and fully natural populations (uncontaminated by allopatric
genomeIn modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
s) probably exist only in isolated places, for example in
CorsicaCorsica is an island in the Mediterranean Sea. It is located west of Italy, southeast of the French mainland, and north of the island of Sardinia....
or in high alpine valleys on the European mainland.
Farming of brown trout has included the production of infertile triploid fish by increasing the water temperature just after fertilisation of eggs, or more reliably by a process known as pressure shocking. Triploids are favoured by
anglersAngling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
because they grow faster and larger than diploid trout. Proponents of the stocking of triploids argue that, because they are infertile, they can be introduced into an environment that contains wild brown trout without the negative effects of cross-breeding. However, it is possible that stocking triploids may damage wild stocks in other ways. Triploids certainly compete with diploid fish for food, space and other resources. They could also be more aggressive than diploid fish and they may disturb spawning behaviour.
Scottish and Irish sea trout populations in recent years have seriously declined due to infestation by
sea liceThe sea louse is a copepod within the order Siphonostomatoida, family Caligidae. There are 36 genera within this family which include approximately 42 Lepeophtheirus and 300 Caligus species...
from salmon farms.
Sea lice infestation from fish farms is unproven and the far more likely cause of lower sea trout numbers is the increase in seal populations due to the demise of commercial bag-netting for salmon. These stations have been bought out and closed down by angling associations but has had the opposite effect in that the proprietors of these stations regularly culled seals.
Further reading
- Clover, Charles. 2004. The End of the Line: How overfishing is changing the world and what we eat. Ebury Press, London. ISBN 0-09-189780-7
External links