is a group of four fish species[4][5] of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, and Great Basin in North America.

Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms.

Several subspecies of cutthroat trout are currently listed as threatened in their native ranges due to habitat loss and the introduction of non-native species.

Cutthroat trout are raised in hatcheries to restore populations in their native range, as well as stock non-native lake environments to support angling.

One side favored subspecies as a valuable taxonomic rank, because they represent important information about their evolutionary and ecological history that should be recognized to preserve biodiversity.

The other side disagreed, arguing that subspecies do not necessarily align with actual evolutionary units, and are simply designations of lineages within a species based on geography.

In short, UIEUs are recognizable population groups that show independence in an evolutionary sense, but do not meet all the criteria to be considered full species.

[16] This, coupled with new information about drainage patterns in western rivers, suggests that the interior radiation and colonization pathways of the cutthroat trout may be different than what was previously thought.

Previously, the first evolutionary theory, based on the work of David Starr Jordan[17] and later Robert J. Behnke,[18][19][20] proposed that an ancestral cutthroat trout from Asia entered North America and dispersed inland through the Columbia River basin.

More recently, an alternative theory[21][22] demonstrates that cutthroat trout originated in the Bonneville Basin and then radiated outwards approximately 4 million years ago.

[59] Depending on subspecies, strain and habitat, most have distinctive red, pink, or orange linear marks along the underside of their mandibles in the lower folds of the gill plates.

[23] At maturity, different populations and subspecies of cutthroat trout can range from 6 to 40 inches (15 to 102 cm) in length, depending on habitat and food availability.

Stream-resident fish are much smaller, 0.4 to 3.2 ounces (11 to 91 g), while lacustrine populations have attained weights ranging from 12 to 17 lb (5.4 to 7.7 kg) in ideal conditions.

[61] Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms.

Eggs hatch into alevins or sac fry in about a month and spend two weeks in the gravel while they absorb their yolk sack before emerging.

[63] 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.

This hybrid generally bears similar coloration and overall appearance to the cutthroat trout, usually retaining the characteristic orange-red slash.

Native cutthroat trout 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.

Scientists believe that the climatic and geologic conditions 3–5 million years ago allowed cutthroat trout from the Snake River to migrate over the divide into the Yellowstone plateau via Two Ocean Pass.

Stream-resident cutthroat trout 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.

In saltwater estuaries and along beaches, Coastal cutthroat trout feed on small fish such as sculpins, sand lance, salmon fry and herring.

[18] 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.

Fish and Wildlife Service exists to restore populations of the Lahontan cutthroat trout (O. h. henshawi) in Pyramid, Walker, Fallen Leaf, June, Marlette, and Gull Lakes and the Truckee River in California and Nevada.

[82] The historic native range of cutthroat trout has been reduced by overfishing, urbanization and habitat loss due to mining, livestock grazing and logging.

As such, populations of genetically pure westslope cutthroat trout are very rare and localized in streams above barriers to upstream migrations by introduced species.

[98] From Alaska to Northern California, coastal cutthroat trout in sea-run, resident stream and lacustrine forms are sought by anglers.

Puget Sound in Washington is a stronghold of sea-run cutthroat trout fishing with its many tributaries and protected saltwater inlets and beaches.

When the grounds are reached, have the oarsman occupy the "stern," as from this position he can manipulate the landing net to a better advantage, the anchor is attached to the "bow."

They average about one and one-half pounds each and are of the salmon myhiss [sic] variety—a catch of 100, three or four hours before sundown, is not unfrequent.In 1902, anticipating the completion of the east entrance road from Cody, Wyoming, Captain Hiram M. Chittenden supervised the construction of the first "Fishing Bridge" across the outlet of Yellowstone Lake.