Trout

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Brown trout Salmo trutta.jpg
Brown trout

Trout (pl.: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera Oncorhynchus , Salmo and Salvelinus , all of which are members of the subfamily Salmoninae in the family Salmonidae. The word trout is also used for some similar-shaped but non-salmonid fish, such as the spotted seatrout/speckled trout (Cynoscion nebulosus, which is actually a croaker).

Contents

Trout are closely related to salmon and have similar migratory life cycles. Most trout are strictly potamodromous, spending their entire lives exclusively in freshwater lakes, rivers and wetlands and migrating upstream to spawn in the shallow gravel beds of smaller headwater creeks. The hatched fry and juvenile trout, known as alevin and parr, will stay upstream growing for years before migrating down to larger waterbodies as maturing adults. There are some anadromous species of trout, such as the steelhead (a coastal subspecies of rainbow trout) and sea trout (the sea-run subspecies of brown trout), that can spend up to three years of their adult lives at sea before returning to freshwater streams for spawning, in the same fashion as a salmon run. Brook trout and three other extant species of North American trout, despite the names, are actually char (or charr), which are salmonids also closely related to trout and salmon.

Trout are classified as oily fish [1] and have been important food fish for humans. As mid-level predators, trout prey upon smaller aquatic animals including insects, crustaceans, baitfish and tadpoles, and themselves in turn are also important staple prey items for many wildlifes including brown bears, otters, raccoons, birds of prey (e.g. sea eagles, ospreys, fish owls), gulls, cormorants and kingfishers, and other large aquatic predators. Discarded remains of trout also provide a source of nutrients for scavengers, detrivores and riparian florae, making trout keystone species across aquatic and terrestrial ecosystems.

Species

The name "trout" is commonly used for many (if not most) species in three of the seven genera in the subfamily Salmoninae: Salmo (Atlantic), Oncorhynchus (Pacific) and Salvelinus (circum-arctic). Fish species referred to as trout include:

Salmo: marble trout, S. marmoratus Marble trout from zadlascica.jpg
Salmo : marble trout, S. marmoratus
Oncorhynchus: rainbow trout, O. mykiss Rainbow Trout.jpg
Oncorhynchus : rainbow trout, O. mykiss
Salvelinus: brook trout, S. fontinalis Brook trout 1918.jpg
Salvelinus : brook trout, S. fontinalis

Fish from other families

Anatomy

Trout that live in different environments can have dramatically different colorations and patterns. Mostly, these colors and patterns form as camouflage, based on the surroundings, and will change as the fish moves to different habitats. Trout in, or newly returned from the sea, can look very silvery, while the same fish living in a small stream or in an alpine lake could have pronounced markings and more vivid coloration; it is also possible that in some species, this signifies that they are ready to mate. In general, trout that are about to breed have extremely intense coloration and can look like an entirely different fish outside of spawning season. It is virtually impossible to define a particular color pattern as belonging to a specific breed; however, in general, wild fish are claimed to have more vivid colors and patterns.

Trout have fins entirely without spines, and all of them have a small adipose fin along the back, near the tail. The pelvic fins sit well back on the body, on each side of the anus. The swim bladder is connected to the esophagus, allowing for gulping or rapid expulsion of air, a condition known as physostome. Unlike many other physostome fish, trout do not use their bladder as an auxiliary device for oxygen uptake, relying solely on their gills.

There are many species, and even more populations, that are isolated from each other and morphologically different. However, since many of these distinct populations show no significant genetic differences, what may appear to be a large number of species is considered a much smaller number of distinct species by most ichthyologists. The trout found in the eastern United States are a good example of this. The brook trout, the aurora trout, and the (extinct) silver trout all have physical characteristics and colorations that distinguish them, yet genetic analysis shows that they are one species, Salvelinus fontinalis.

Lake trout (Salvelinus namaycush), like brook trout, belong to the char genus. Lake trout inhabit many of the larger lakes in North America, and live much longer than rainbow trout, which have an average maximum lifespan of seven years. Lake trout can live many decades, and can grow to more than 30 kilograms (66 lb).

Habitat

A trout farm in Sochi, Russia Forel farm Sochi.jpg
A trout farm in Sochi, Russia

Trout are usually found in cool (50–60 °F or 10–16 °C), clear streams and lakes, although many of the species have anadromous strains as well. Young trout are referred to as troutlet, troutling or fry. They are distributed naturally throughout North America, northern Asia and Europe. Several species of trout were introduced to Australia and New Zealand by amateur fishing enthusiasts in the 19th century, effectively displacing and endangering several upland native fish species. The introduced species included brown trout from England and rainbow trout from California. The rainbow trout were a steelhead strain, generally accepted as coming from Sonoma Creek. The rainbow trout of New Zealand still show the steelhead tendency to run up rivers in winter to spawn. [2]

In Australia the rainbow trout was introduced in 1894 from New Zealand and is an extremely popular gamefish in recreational angling. [3] Despite severely impacting the distribution and abundance of native Australian fish, such as the climbing galaxias, millions of rainbow and other trout species are released annually from government and private hatcheries. [3]

The closest resemblance of seema trout and other trout family can be found in the Himalayan Region of India, Nepal, Bhutan, Pakistan and in Tian Shan mountains of Kyrgyzstan.[ clarification needed ]

Diet

Golden trout, Oncorhynchus aguabonita Truite doree.jpg
Golden trout, Oncorhynchus aguabonita

Trout generally feed on other fish, and soft bodied aquatic invertebrates, such as flies, mayflies, caddisflies, stoneflies, mollusks and dragonflies. In lakes, various species of zooplankton often form a large part of the diet. In general, trout longer than about 300 millimetres (12 in) prey almost exclusively on fish, where they are available. Adult trout will devour smaller fish up to one-third of their length. Trout may feed on shrimp, mealworms, bloodworms, insects, small animal parts, and eel.

Trout who swim the streams love to feed on land animals, aquatic life, and flies. [4] Most of their diet comes from macroinvertebrates, or animals that do not have a backbone like snails, worms, or insects. They also eat flies, and most people who try to use lures to fish trout mimic flies because they are one of trout's most fed on meals. [4] Trout enjoy certain land animals, including insects like grasshoppers. They also eat small animals like mice when they fall in. (Although only large trout have mouths capable of eating mice.) They consume a diet of aquatic life like minnows or crawfish as well. Trout have a diverse diet they follow; they have plenty of different oppositions. [4]

Trout as food

Baked trout Baked trout.jpg
Baked trout

Compared to other salmonids, trout are somewhat more bony, but the flesh is generally considered tasty, and the texture is often indistinguishable from that of salmon. The flavor of the flesh is heavily influenced by the diet of the fish. For example, trout that have been feeding on crustaceans tend to be more flavorful than those feeding primarily on insects and larvae. Because of their popularity, trout are often raised on fish farms and then stocked into heavily fished waters, in an effort to mask the effects of overfishing.[ citation needed ] Farmed trout are also sold commercially as seafood, although they are not saltwater fish. Trout meat is typically prepared the same way as salmon, often by smoking. [5]

In Mainland China, farm-raised rainbow trout from Qinghai was officially sanctioned to be labeled and sold domestically as salmon, which caused much controversy regarding food safety and consumer rights violation, [6] as raw fish dishes or yusheng using Atlantic salmon is gaining popularity in southern China. Farmed rainbow trout is much cheaper than the imported Atlantic salmon and the meat are indistinguishable to the untrained eyes, and the news of trout being sold as salmon triggered public scrutiny accusing seaford suppliers of bait-and-switch and unethical business practices. Also, many people believe freshwater trout are more prone to parasites than oceanic salmon (despite both live in freshwater for significant periods of their life cycle) and thus unsafe for raw eating.

Nutritional value

One fillet of trout (about 79 g or 2.8 oz) contains: [7]

Trout fishing

Trout are very popular freshwater game fish highly prized especially by creek fishermen, because they generally put up a good fight when caught with a hook and line. As trout are predatory fish, lure fishing (which use replica baits called lures to imitate live prey) is the predominant form of sport fishing involving trout, although traditional bait fishing techniques using floats and/or sinkers (particularly with moving live baits such as baitfish, crayfish or aquatic insects) are also successful, especially against stocked trout that are hatchery/farm-raised and thus more accustomed to artificial feeds.

Many species of trout, most noticeably rainbow trout and brown trout, have been widely introduced into waterbodies outside of their native ranges purely for the sake of recreational fishing, and some of these introduced populations have even become invasive in the new habitats.

River fishing

While trout can be caught with a normal rod and reel, fly fishing is a distinctive lure fishing method developed for trout, and now extended to other species. Due to the high proportion of insects and small crustaceans within the trout's diet, small lures made of hand-tied hairs and threads are often used to imitate these aquatic invertebrates that the trout prey upon. These ultralight fly lures cannot be cast adequately by conventional techniques, and a specialized heavy line (i.e. fly line) is needed to launch the lure.

Understanding how moving water shapes the stream channel makes it easier to find trout. In most streams, the current creates a riffle-run-pool pattern that repeats itself over and over. A deep pool may hold a big brown trout, but rainbow trout and smaller brown trout are likely found in runs. Riffles are where fishers will find small trout, called troutlet, during the day and larger trout crowding in during morning and evening feeding periods. [8]

Ice fishing

Fishing for trout under the ice generally occurs in depths of 4 to 8 feet (1.2 to 2.4 m). Because trout are cold water fish, during the winter they move from up-deep to the shallows, replacing the small fish that inhabit the area during the summer. Trout in winter constantly cruise in shallow depths looking for food, usually traveling in groups, although bigger fish may travel alone and in water that's somewhat deeper, around 12 feet (3.7 m). Rainbow, Brown, and Brook trout are the most common trout species caught through the ice. [9]

Trout fishing records

By information from International Game Fish Association (IGFA), the most outstanding records are: [10]

Baits

Declines in native trout populations

Salmonid populations in general have been declining due to numerous factors, including invasive species, hybridization, wildfires, and climate change. Native salmonid fish in the western and southwestern United States are threatened by non-native species that were introduced decades ago. Non-native salmonids were introduced to enrich recreational fishing; [11] however, they quickly started outcompeting and displacing native salmonids upon their arrival. Non-native, invasive species are quick to adapt to their new environment and learn to outcompete any native species, making them a force the native salmon and trout have to reckon with. Not only do the non-native fish drive the native fish to occupy new niches, but they also try to hybridize with them, contaminating the native gene construction. As more hybrids between native and non-native fish are formed, the lineage of the pure fish is continuously being contaminated by other species and soon may no longer represent the sole native species. The Rio Grande cutthroat trout (Oncorhynchus clarki virginalis) are susceptible to hybridization with other salmonids such as rainbow trout (Oncorhynchus mykiss) and yield a new "cutbow" trout, which is a contamination of both lineages’ genes. One solution to this issue is implemented by New Mexico Department of Game and Fish hatcheries: stock only sterile fish in river streams. Hatcheries serve as a reservoir of fish for recreational activities but growing and stocking non-sterile fish would worsen the hybridization issue on a quicker, more magnified time scale. By stocking sterile fish, the native salmonids can't share genes with the non-native hatchery fish, thus, preventing further gene contamination of the native trout in New Mexico. Fire is also a factor in deteriorating Gila trout (Oncorhynchus gilae) populations because of the ash and soot that can enter streams following fires. [12] The ash lowers water quality, making it more difficult for the Gila trout to survive. In some New Mexico streams, the native Gila trout will be evacuated from streams that are threatened by nearby fires and be reintroduced after the threat is resolved.

Climate change is also dwindling native salmonid populations. Global warming continually affects various cold-water fish such as trout, especially as inland waterbodies are more prone to warming than oceans. With an increase of temperature along with changes in spawning river flow, an abundance of trout species are effected negatively. In the past, a mere 8 °F (4.4 °C) increase was predicted to eliminate half of the native brook trout in the Southern Appalachian Mountains. [13] Trout generally prefer streams with colder water (50–60 °F or 10–16 °C) to spawn and thrive, but raising water temperatures are altering this ecosystem and further deteriorate native populations.

See also

Related Research Articles

<span class="mw-page-title-main">Salmonidae</span> Family of ray-finned fishes

Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes, consisting of 11 extant genera and over 200 species collectively known as "salmonids" or "salmonoids". The family includes salmon, trout, char, graylings, freshwater whitefishes, taimens and lenoks, all coldwater mid-level predatory fish that inhabit the subarctic and cool temperate waters of the Northern Hemisphere. The Atlantic salmon, whose Latin name became that of its genus Salmo, is also the eponym of the family and order names.

<span class="mw-page-title-main">Rainbow trout</span> Fresh-water species of fish

The rainbow trout is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead is an anadromous (sea-run) form of the coastal rainbow trout(O. m. irideus) or Columbia River redband trout (O. m. gairdneri) that usually returns to freshwater to spawn after living two to three years in the ocean. Freshwater forms that have been introduced into the Great Lakes and migrate into tributaries to spawn are also called steelhead.

Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout (Oncorhynchus mykiss irideus) or Columbia River redband trout. Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and North America. Like other sea-run (anadromous) trout and salmon, steelhead spawn in freshwater, smolts migrate to the ocean to forage for several years and adults return to their natal streams to spawn. Steelhead are iteroparous, although survival is approximately 10–20%.

<span class="mw-page-title-main">Brook trout</span> Species of fish

The brook trout is a species of freshwater fish in the char genus Salvelinus of the salmon family Salmonidae. It is native to Eastern North America in the United States and Canada, but has been introduced elsewhere in North America, as well as to Iceland, Europe, and Asia. In parts of its range, it is also known as the eastern brook trout, speckled trout, brook charr, squaretail, brookie or mud trout, among others. A potamodromous population in Lake Superior, is known as coaster trout or, simply, as coasters. Anadromous populations which are found in coastal rivers from Long Island to Hudson Bay are sometimes referred to as salters. The brook trout is the state fish of nine U.S. states: Michigan, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Vermont, Virginia, and West Virginia, and the Provincial Fish of Nova Scotia in Canada.

<span class="mw-page-title-main">Cutthroat trout</span> Species of fish

The cutthroat trout(Oncorhynchus clarkii) is a fish species of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, and Great Basin in North America. As a member of the genus Oncorhynchus, it is one of the Pacific trout, a group that includes the widely distributed rainbow trout. Cutthroat trout are popular gamefish, especially among anglers who enjoy fly fishing. The common name "cutthroat" refers to the distinctive red coloration on the underside of the lower jaw. The specific name clarkii was given to honor explorer William Clark, coleader of the Lewis and Clark Expedition.

<span class="mw-page-title-main">Golden trout</span> Species of fish

The Californiagolden trout (Oncorhynchus aguabonita or Oncorhynchus mykiss aguabonita), is a species of trout native to California. The golden trout is normally found in the Golden Trout Creek, Volcano Creek, and the South Fork Kern River. The Golden trout is the official freshwater state fish of California since 1947.

<span class="mw-page-title-main">Apache trout</span> Species of fish

The Apache trout or Arizona trout, Oncorhynchus apache, is a species of freshwater fish in the salmon family of order Salmoniformes. It is one of the Pacific trouts.

<span class="mw-page-title-main">Bitterroot River</span> River in Montana, United States

The Bitterroot River is a northward flowing 84-mile (135 km) river running through the Bitterroot Valley, from the confluence of its West and East forks near Conner in southern Ravalli County to its confluence with the Clark Fork River near Missoula in Missoula County, in western Montana. The Clark Fork River is a tributary to the Columbia River and ultimately, the Pacific Ocean. The Bitterroot River is a Blue Ribbon trout fishery with a healthy population of native westslope cutthroat trout and bull trout. It is the third most fly fished river in Montana behind the Madison and Big Horn Rivers.

<i>Oncorhynchus</i> Genus of fishes

Oncorhynchus is a genus of ray-finned fish in the subfamily Salmoninae of the family Salmonidae, native to coldwater tributaries of the North Pacific basin. The genus contains twelve extant species, namely six species of Pacific salmon and six species of Pacific trout, all of which are migratory mid-level predatory fish that display natal homing and semelparity.

<span class="mw-page-title-main">Lahontan cutthroat trout</span> Subspecies of fish

Lahontan cutthroat trout is the largest subspecies of cutthroat trout, and the state fish of Nevada. It is one of three subspecies of cutthroat trout that are listed as federally threatened.

<span class="mw-page-title-main">Westslope cutthroat trout</span> Subspecies of fish

The westslope cutthroat trout, also known as the black-spotted trout, common cutthroat trout and red-throated trout is a subspecies of the cutthroat trout and is a freshwater fish in the salmon family of order Salmoniformes. The cutthroat is the Montana state fish. This subspecies is a species of concern in its Montana and British Columbia ranges and is considered threatened in its native range in Alberta.

<span class="mw-page-title-main">Coastal cutthroat trout</span> Subspecies of fish

The coastal cutthroat trout, also known as the sea-run cutthroat trout, blue-back trout or harvest trout, is one of the several subspecies of cutthroat trout found in Western North America. The coastal cutthroat trout occurs in four distinct forms. A semi-anadromous or sea-run form is the most well known. Freshwater forms occur in both large and small rivers and streams and lake environments. The native range of the coastal cutthroat trout extends south from the southern coastline of the Kenai Peninsula in Alaska to the Eel River in Northern California. Coastal cutthroat trout are resident in tributary streams and rivers of the Pacific basin and are rarely found more than 100 miles (160 km) from the ocean.

<span class="mw-page-title-main">Beardslee trout</span> Freshwater fish

The Beardslee trout, formerly Salmo gairdneri beardsleei) is a local form of rainbow trout endemic to Lake Crescent in Washington. Some sources treat them as a subspecies.

<span class="mw-page-title-main">Cutbow</span> A hybrid between a cutthroat trout and rainbow trout

A cutbow is an interspecific fertile hybrid between a rainbow trout and a cutthroat trout. Cutbow hybrids may occur naturally where the native ranges of both species overlap, such as between coastal rainbow trout and coastal cutthroat trout and between Columbia River redband trout and westslope cutthroat trout. While natural separation of spawning habitat limited hybridization in most native populations of rainbows and cutthroats, introduction of non-native hatchery-raised rainbow trout into the native ranges of cutthroat subspecies increased the rate of hybridization. Some native cutthroat populations are, as a result, at risk due to genetic pollution.

<span class="mw-page-title-main">Kype</span>

A kype is a hook-like secondary sex characteristic which develops at the distal tip of the lower jaw in some male salmonids prior to the spawning season. The structure usually develops in the weeks prior to, and during, migration to the spawning grounds. In addition to the development of the kype, a large depression forms in the two halves of the premaxilla in the upper jaw, allowing the kype to fit into the premaxilla when the mouth is closed.

Fishing in Colorado has brought in a large amount of revenue for the state. In 2019 Colorado Parks and Wildlife estimated outdoor recreation contributed roughly 62 billion dollars to the state economy. Fishing was reported to be the 5th most popular outdoor activity and 110, 511 fishing and hunting combination licenses were sold. Ice fishing makes up part of this total fishing revenue and is a common annual sport for Colorado residents and out-of-state visitors. There is no legal definition of ice fishing season. Rather, people begin to ice fish once the lakes freeze over with thick enough ice. Colorado Parks and Wildlife also recommend that people always ice-fish with another person. Typically, this starts in December and ends in April for Colorado. Lakes size, depth, elevation, and seasonal weather can cause variance to the season. Once the lakes freeze over with thick enough ice, anglers go out onto the ice, drill holes through the ice, and fish for a variety of species.

References

  1. "What are oily fish?". Food Standards Agency. June 23, 2004. Archived from the original on December 4, 2013. Retrieved February 17, 2013.
  2. Landergren, Peter (1999). "Spawning of anadromous rainbow trout, Oncorhynchus mykiss (Walbaum): A threat to sea trout, Salmo trutta L., populations?". Fisheries Research. 40: 55–63. doi:10.1016/S0165-7836(98)00215-X.
  3. 1 2 Gomon, Martin; Bray, Dianne. "Rainbow Trout, Oncorhynchus mykiss". Fishes of Australia. Archived from the original on September 4, 2014. Retrieved August 30, 2014.
  4. 1 2 3 "Trout Food | Stream Explorers". www.streamexplorers.org. Retrieved April 9, 2020.
  5. Tennant, S. G. B. (2000). Trout. Willow Creek Press. p. 27. ISBN   978-1-57223-276-1.
  6. Zheng, Sarah (August 15, 2018). "Is rainbow trout the same as salmon? China says yes despite food safety fears". South China Morning Post . Retrieved May 8, 2023.
  7. "Search the USDA National Nutrient Database for Standard Reference". Nal.usda.gov. Archived from the original on March 3, 2015. Retrieved December 26, 2011.
  8. "Cotrout - The Outdoor Resources". Cotrout. Retrieved June 3, 2019.
  9. Straw, Matt (December 5, 2012). "Ice Fishing Trout". In-Fisherman. Retrieved February 7, 2023.
  10. "IGFA World Records". International Game Fish Association. Retrieved November 1, 2015.
  11. Quist, Michael (2004). "Bioinvasive species and the preservation of cutthroat trout in the western United States: ecological, social, and economic issues". Environmental Science & Policy. 7 (4): 303–313. doi:10.1016/j.envsci.2004.05.003.
  12. "Gila Trout Recovery and Angling". New Mexico Department of Game and Fish. Retrieved December 2, 2019.
  13. Climate Change and Cold Water Fish. United States Environmental Protection Agency. 1999.

Further reading