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|Coastal cutthroat trout, Oncorhynchus clarki clarki, the type subspecies|
(J. Richardson, 1836)
Oncorhynchus clarki clarki
|Coastal cutthroat trout, Oncorhynchus clarki clarki, the type subspecies|
(J. Richardson, 1836)
Oncorhynchus clarki clarki
The cutthroat trout (Oncorhynchus clarki) is a fish species of the salmonidae family 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 clarki was given to honor explorer William Clark, coleader of the Lewis and Clark Expedition.
Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms and clear, cold, moderately deep lakes. They are native to the alluvial or freestone streams that are typical tributaries of the Pacific basin, Great Basin and Rocky Mountains. Cutthroat trout spawn in the spring and may inadvertantly but naturally hybridize with rainbow trout, producing fertile cutbows. Some populations of the coastal cutthroat trout (O. c. clarki) are semi-anadromous.
Several subspecies of cutthroat are currently listed as threatened in their native ranges due to habitat loss and introduction of non-native species. Two subspecies, O. c. alvordensis and O. c. macdonaldi, are considered extinct. Cutthroat trout are raised in hatcheries to restore native populations, as well as stock non-native lake environments to support angling.
The cutthroat trout type species and several subspecies are the state fish in seven western U.S. states.
The scientific name of the cutthroat trout is Oncorhynchus clarki. They were the first trout encountered by Europeans when in 1541 Spanish explorer Francisco de Coronado recorded seeing trout, most likely Rio Grande cutthroat trout (O. c. virginalis) in the Pecos River near Santa Fe, New Mexico. The species was first described in the journals of explorer William Clark from specimens obtained during the Lewis and Clark Expedition from the Missouri River near Great Falls, Montana. These were most likely the westslope cutthroat trout (O. c. lewisi). Cutthroat trout were given the name Salmo clarki in honor of William Clark, who co-led the expedition of 1804–1806. One of Lewis and Clark's missions was to describe the flora and fauna encountered during the expedition. The type specimen of S. clarki was described by naturalist John Richardson from a tributary of the lower Columbia River, identified as the "Katpootl", which was perhaps the Lewis River as there was a Multnomah village of similar name at the confluence. This type specimen was most likely the coastal cutthroat subspecies.
In 1989, morphological and genetic studies indicated trout of the Pacific basin were genetically closer to Pacific salmon (Oncorhynchus species) than to the Salmos–brown trout (S. trutta) or Atlantic salmon (S. salar) of the Atlantic basin. Thus, in 1989, taxonomic authorities moved the rainbow, cutthroat and other Pacific basin trout into the genus Oncorhynchus.
The 14 recognized subspecies of cutthroats are each native to a separate geographic area. The cutthroat trout is thought by scientists to have evolved over the past two million years from other Oncorhynchus species that migrated up the Columbia and Snake River basins.
|Geographical group||Common name||Scientific name||Range||Image|
|Pacific Coast||Coastal cutthroat trout, also known as "sea-run" cutthroat||O. c. clarki (J. Richardson, 1836)||Native in coastal tributaries from northern California to Alaska. O. c. clarki is the type subspecies for cutthroat trout.|
O. c. clarki
Coastal cutthroat trout
|Crescenti trout||O. c. crescenti||No longer a recognized subspecies, but is a unique population of coastal cutthroats endemic to Lake Crescent, Washington.|
|Great Basin||Alvord cutthroat trout||O. c. alvordensis† (Behnke 2002)||Was endemic to tributaries of Alvord Lake in southeastern Oregon; it is considered extinct.|
O. c. utah
Bonneville cutthroat trout
|Bonneville cutthroat trout||O. c. utah (G. Suckley, 1874)||Native to tributaries of the Great Salt Lake.|
|Humboldt cutthroat trout||O. c. ssp. (Behnke and Trotter, 2008),||Found only in the upper Humboldt River of northern Nevada. Considered by the Nevada Division of Wildlife to be a population of O. c. henshawi.|
|Lahontan cutthroat trout||O. c. henshawi (Gill and Jordan, 1878)||Native in western Nevada. Is designated as threatened (1975).|
|Whitehorse Basin cutthroat trout||O. c. ssp., considered a separate subspecies by Behnke (2002)||Native to southeastern Oregon. Considered a distinct population segment of Lahontan cutthroat trout by the U.S. Fish and Wildlife Service.|
|Paiute cutthroat trout||O. c. seleniris (J. O. Snyder, 1933)||Endemic to eastern Sierra Nevada Mountains, and is designated as threatened (1975).|
|Northern Rockies||Snake River fine-spotted cutthroat trout||O. c. behnkei (Montgomery, 1995)||Considered by some as a population of O. c. bouvieri. It is native to the Snake River of Idaho and Wyoming.|
O. c. behnkei
Snake River fine-spotted cutthroat trout
O. c. bouvieri
Yellowstone cutthroat trout
|Westslope cutthroat trout||O. c. lewisi (G. Suckley, 1856)||Native to northern Idaho, Montana, British Columbia, and Alberta.|
|Yellowfin cutthroat trout||O. c. macdonaldi† (Jordan & Fisher, 1891)||Was endemic to Twin Lakes, Colorado; it is now extinct.|
|Yellowstone cutthroat trout||O. c. bouvieri (Jordan and Gilbert, 1883)||Native to the upper Snake River, Yellowstone Lake, and Yellowstone River, in Idaho, Montana and Wyoming.|
|Southern Rockies||Colorado River cutthroat trout||O. c. pleuriticus (Cope, 1872)||Native to tributaries of the Green and Colorado Rivers.|
O. c. virginalis
Rio Grande cutthroat trout
|Greenback cutthroat trout||O. c. stomias (Cope, 1871)||Native to the Arkansas and South Platte Rivers in eastern Colorado; it is designated as threatened (1978).|
|Rio Grande cutthroat trout||O. c. virginalis (C. F. Girard, 1856)||Native to New Mexico and southern Colorado.|
Throughout their native and introduced ranges, cutthroat trout vary widely in size, coloration and habitat selection. Though their coloration can range from golden to gray to green on the back, and depending on subspecies, strain and habitat, they usually feature distinctive red, pink, or orange linear marks along the undersides of their mandibles in the lower folds of the gill plates. These markings are responsible for the common name "cutthroat" given to the trout by outdoor writer Charles Hallock in an 1884 article in The American Angler. Some coastal rainbow trout (Oncorhynchus mykiss irideus) and redband trout (O. m. gairdneri) populations also display reddish or pink throat markings. Inland subspecies of the cutthroat trout are distinguished from the coastal cutthroat, rainbow trout and cutbow hybrids by a distinct lack of spotting on the top of the head. At maturity, different populations and subspecies of cutthroats can range from 6 to 40 in (15 to 102 cm) in length, depending on habitat and food availability. The sea-run forms of coastal cutthroat average 2 to 5 lb (0.9 to 2.3 kg), while stream-resident forms attain much smaller sizes, 0.4 to 3.2 oz (11 to 91 g). Lacustrine populations have attained weights from 12 to 17 lb (5.4 to 7.7 kg) in ideal conditions. The length and weights of mature inland forms vary widely depending on their particular environment and availability of food. The largest of the cutthroat subspecies is the Lahontan cutthroat trout (O. c. henshawi). These fish average 8 to 9 in (20 to 23 cm) in small streams and 8 to 22 in (20 to 56 cm) in larger rivers and lakes. In ideal environments, the Lahonton cutthroat attains typical weights of 0.25 to 8 lb (0.11 to 3.63 kg). The world record cutthroat is a Lahonton at 39 in (99 cm) and 41 lb (19 kg).
Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms. They are native to the alluvial or freestone streams that are typical tributaries of the Pacific Basin, Great Basin and Rocky Mountains. They spawn in the spring, as early as February in coastal rivers and as late as July in high mountain lakes and streams. Spawning begins when water temperatures reach 43 to 46°F (6 to 8°C). Lake-resident cutthroat trout are usually found in moderately deep, cool lakes with adequate shallows and vegetation for good food production. Lake populations generally require access to gravel-bottomed streams to be self-sustaining, but occasionally spawn on shallow gravel beds with good water circulation.
Cutthroats naturally interbreed with the closely related rainbow trout, producing fertile hybrids commonly called "cutbows". As this hybrid generally bears similar coloration and overall appearance to the cutthroat, retaining the characteristic orange-red slash, these hybrids often pose a taxonomical difficulty. In addition, cutthroats may hybridize with the O. gilae subspecies, the Gila trout and Apache trout in regions where their ranges overlap.
Cutthroat trout are native to western North America. The cutthroat species has evolved through geographic isolation into many subspecies, each native to a different major drainage basin. Native cutthroat species are found along the Pacific Northwest coast from Alaska through British Columbia into northern California, in the Cascade Range, the Great Basin and throughout the Rocky Mountains including southern Alberta. Some coastal populations of the coastal cutthroat trout (O. c. clarki) are semianadromous, spending a few months in marine environments to feed as adults and returning to fresh water from fall through early spring to feed on insects and spawn. Cutthroat trout have the second-largest historic native range of North American trout, the lake trout having the largest. Ranges of some subspecies, particularly the westslope cutthroat trout (O. c. lewisi) have been reduced to less than 10% of their historic range due to habitat loss and introduction of non-native species.
Cutthroat trout have been introduced into non-native waters outside their historic native range, but not to the extent of the rainbow trout (O. mykiss). Cutthroats were introduced into Lake Michigan tributaries in the 1890s and sporadically in the early 20th century, but never established wild populations. A population of Yellowstone cutthroats purportedly has been established in Lake Huron. Although cutthroat trout are not native to Arizona, they are routinely introduced by the Arizona Game and Fish Department into high mountain lakes in the White Mountains in northeast Arizona.
Cutthroat trout require cold, clear, well-oxygenated, shallow rivers with gravel bottoms or cold, moderately deep lakes. Healthy stream-side vegetation that reduces siltation is typical of healthy cutthroat habitat. Beaver ponds may provide refuge during periods of drought and over winter. Most populations stay in fresh water throughout their lives and are known as nonmigratory, stream-resident or riverine populations. The coastal cutthroat trout (O. c. clarki) is the only cutthroat subspecies to coevolve through its entire range with the coastal rainbow trout (O. m. irideus). Portions of the westslope cutthroat trout's (O. c. lewisi) range overlap with the Columbia river redband trout (O. m. gairdneri), but the majority of its native range is in headwater tributary streams above major waterfalls and other barriers to upstream migration. At least three subspecies are confined to isolated basins in the Great Basin and can tolerate saline or alkaline water.
Cutthroat trout are opportunistic feeders. Stream-resident cutthroats primarily feed on larval, pupal and adult forms of aquatic insects (typically caddisflies, stoneflies, mayflies and aquatic dipterans), and adult forms of terrestrial insects (typically ants, beetles, grasshoppers and crickets) that fall into the water, fish eggs, small fish, along with crayfish, shrimp and other crustaceans. As they grow the proportion of fish consumed increases in most populations. Coastal cutthroats feed in salt water on crustaceans and fishes while in fresh water they consume aquatic insects and crustaceans, frogs, earthworms, fishes, fish eggs, salamanders, etc. Within the range of the bull trout (Salvelinus confluentus) the cutthroat is a forage fish for the piscivorous bull trout.
Various subspecies of cutthroat trout are raised in commercial, state and federal hatcheries for introduction into suitable native and non-native riverine and lacustrine environments. In the early 20th century, several hatcheries were established in Yellowstone National Park by the U.S. Bureau of Fisheries. These hatcheries not only produced stocks of the Yellowstone cutthroat trout (O. c. bouvieri) for the park, but also took advantage of the great spawning stock of cutthroat trout to supply eggs to hatcheries around the U.S. Between 1901 and 1953, 818 million trout eggs were exported from the park to hatcheries throughout the U.S. The Lahontan National Fish Hatchery operated by the U.S. Fish and Wildlife Service exists to restore populations of the Lahontan cutthroat trout (O. c. lahontan) in Pyramid, Walker, Fallen Leaf, June, Marlette, and Gull Lakes and the Truckee River in California and Nevada. The hatchery produces about 300,000–400,000 Lahonton cutthroat trout fry annually. The Jackson National Fish Hatchery produces around 400,000 Snake River fine-spotted cutthroat trout (O. c. behnkei) annually to support fisheries in Idaho and Wyoming. The Leadville National Fish Hatchery produces 125,000–200,000 Snake River fine-spotted, greenback cutthroat and rainbow trout annually to support fishing in the Fryingpan and Arkansas River drainages and other Colorado waters. The Bozeman Fish Technology Center, formerly a cutthroat trout fish hatchery in Bozeman, Montana, plays a major role in the restoration of the greenback (O. c. stomias) and westslope cutthroat trout (O. c. lewisi) subspecies.
The historic native range of cutthroat trout has been reduced by overfishing, urbanization and habitat loss due to mining, grazing and logging. Population densities have been reduced and in some cases populations have disappeared though competition with non-native brook, brown and rainbow trout, which were introduced in the late 19th and early 20th centuries. The most serious current threats to several subspecies are interspecific breeding with introduced rainbow trout creating hybrid cutbows and intraspecific breeding with other introduced cutthroat subspecies. In the Greater Yellowstone Ecosystem, the presence of lake trout (Salvelinus namaycush) in Yellowstone Lake in Yellowstone National Park has caused serious decline in (O. c. bouvieri). Outbreaks of whirling disease in major spawning tributaries within the native ranges have also caused declines.
Interspecific and intraspecific breeding
The most serious impact on the genetic purity of most cutthroat trout subspecies results from interspecific and intraspecific breeding resulting in hybrids that carry the genes of both parents. In inland populations, the introduction of rainbow trout from hatchery stocks have resulted in cutbow hybrids that continue to diminish the genetic purity of many cutthroat subspecies. The introduction of hatchery-raised Yellowstone cutthroat trout into native ranges of other cutthroat subspecies, particularly the westslope cutthroat trout, has resulted in intraspecific breeding and diminished genetic purity of the westslope subspecies. As such, populations of genetically pure westslope cutthroat trout are very rare and localized in streams above barriers to upstream migrations by introduced species. Fisheries biologist Robert J. Behnke attributes the extinction of the yellowfin cutthroat trout (O. c. macdonaldi) and Alvord cutthroat trout (O. c. alvordensis) subspecies to the introduction of non-native rainbow trout.
Decline of the Yellowstone cutthroat
The population at the core of the Yellowstone cutthroat trout's native range, in Yellowstone Lake, crashed in the 1960s due to overharvest of fish by anglers and eggs by hatchery personnel in the early 20th century. A change in management approach to catch and release fishing and termination of hatchery operations in the park allowed the cutthroats to recover. Then in 1994, park officials discovered lake trout in Yellowstone Lake. Although lake trout were established in Shoshone, Lewis and Heart lakes in the Snake River drainage from U.S. government stocking operations in 1890, they were never officially introduced into the Yellowstone River drainage and their presence there is probably the result of accidental or illegal introductions. By 2000, the cutthroat population has declined to less than 10% of its early 20th-century abundance. However, aggressive lake trout eradication programs have killed over one million lake trout since 1996, and the cutthroat population in the lake seems to be rebounding. Cutthroat trout co-exist with lake trout in Heart lake, an isolated back-country lake at the head of the Heart River that gets little angling pressure.
Most subspecies of cutthroat trout are highly susceptible to whirling disease (Myxobolus cerebralis). The Snake River fine-spotted cutthroat trout appears to be resistant to the parasite.
Cutthroat trout are prized as a gamefish, particularly by fly anglers. From the Yellowstone cutthroat trout fishery in Yellowstone National Park, the unique Lahontan cutthroat trout fishery in Pyramid Lake Nevada, the small stream fisheries of the westslope cutthroat to saltwater angling for sea-run cutthroat on the Pacific coast, cutthroat trout are a popular quarry for trout anglers throughout their ranges. The all-tackle world record is 41 lb (19 kg) caught in Pyramid Lake in December 1925. Their propensity to feed on aquatic and terrestrial insects make them an ideal quarry for the fly angler.
The cutthroat trout is the state fish of Idaho, Montana and Wyoming, while particular subspecies of cutthroat are the state fish of Colorado, Nevada, New Mexico and Utah.
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