endemic to a single nation
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Native to the Snake River system above Shoshone Falls (except for waters between Jackson Lake and Palisades Reservoir) and Yellowstone River drainage downstream to the Tongue River; also native to the Goose Creek drainage in Nevada and the Raft River drainage in northwestern Utah (extirpated in the latter area) (Behnke 2002). Lakes with large populations include Yellowstone Lake and Henry's Lake; the latter population is slightly hybridized (Behnke 1992). In the upper Snake River drainage and in tributaries of the Yellowstone River downstream from Yellowstone Park, has been largely replaced by non-native and/or hybrid trout (Behnke 1992, 2002). Over the past several decades, millions have been stocked outside the native range, especially in the native range of the westslope cutthroat trout (Behnke 1992).
Montana Valley and Foothill Grasslands Habitat
This taxon can be found in the Montana valley and foothill grasslands ecoregions, along with some other North American ecoregions. This ecoregion occupies high valleys and foothill regions in the central Rocky Mountains of Montana in the USA and Alberta, Canada. The ecoregion the uppermost flatland reaches of the Missouri River drainage involving part of the Yellowstone River basin, and extends into the Clark Fork-Bitterroot drainage of the Columbia River system. The ecoregion, consisting of three chief disjunctive units, also extends marginally into a small portion of northern Wyoming. Having moderate vertebrate species richness, 321 different vertebrate taxa have been recorded here.
The dominant vegetation type of this ecoregion consists chiefly of wheatgrass (Agropyron spp.) and fescue (Festuca spp.). Certain valleys, notably the upper Madison, Ruby, and Red Rock drainages of southwestern Montana, are distinguished by extensive sagebrush (Artemisia spp.) communities as well. This is a reflection of semi-arid conditions caused by pronounced rain shadow effects and high elevation. Thus, near the Continental Divide in southwestern Montana, the ecoregion closely resembles the nearby Snake/Columbia shrub steppe.
A number of mammalian species are found in the ecoregion, including: American Pika (Ochotona princeps), a herbivore preferring talus habitat; Bighorn Sheep (Ovis canadensis), Black-tailed Prairie Dog (Cynomys ludovicianus), who live in underground towns that may occupy vast areas; Brown Bear (Ursos arctos); Hoary Marmot (Marmota caligata), a species who selects treeless meadows and talus as habitat; and the Northern River Otter (Lontra canadensis), a species that can tolerate fresh or brackish water and builds its den in the disused burrows of other animals.
There are six distinct anuran species that can be found in the Montana valleys and foothills grasslands, including: Canadian Toad (Anaxyrus hemiophrys); Western Toad (Anaxyrus boreas); Northern Leopard Frog (Lithobates pipiens); Plains Spadefoot Toad (Spea bombifrons); Columbia Spotted Frog (Rana luteiventris), an anuran that typically breeds in shallow quiet ponds; and the Boreal Chorus Frog (Pseudacris maculata).
Exactly two amphibian taxa occurr in the ecoregion: Long-toed Salamander (Ambystoma macrodactylum), a species who prefers lentic waters and spends most of its life hidden under bark or soil; Tiger Salamander (Ambystoma tigrinum).
Reptilian species within the ecoregion are: Milk Snake (Lampropeltis triangulum), an adaptable taxon that can be found on rocky slopes, prairie and near streambeds; Painted Turtle (Chrysemys picta); Western Plains Garter Snake (Thamnophis radix), a taxon that can hibernate in the burrows of rodents or crayfish or even hibernate underwater; Yellow-bellied Racer (Coluber constrictor); Spiny Softshell Turtle (Apalone spinifera); Western Terrestrial Garter Snake (Thamnophis elegans); Rubber Boa (Charina bottae); Western Skink (Plestiodon skiltonianus); and the Western Rattlesnake (Crotalis viridis).
The ecoregion supports endemic and relict fisheries: Westslope Cutthroat Trout (Oncorhynchus clarki lewisi), Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri), and fluvial Arctic Grayling (Thymallus arcticus), a relict species from past glaciation.
- C. Michael Hogan & World Wildlife Fund. 2014."Montana Valley and Foothill Grasslands". Encyclopedia of Earth, National Council for Science and the Environment, Washington DC ed.Mark McGinley.
- Matthew Jaeger, Ken Frazer, Clark Nelson, Mike Vaughn, Brad Schmitz, Jim Darling. 2005. Movements and habitat use of Yellowstone native fishes and reptiles and nesting distributions of native birds. T2-25-2 Report. Montana Department of Fish, Wildlife and Parks. Miles City, MT
Habitat Type: Freshwater
Comments: Rivers, creeks, beaver ponds, large lakes; optimum water temperature generally may be 4.5-15.5 C, but tolerance of much warmer temperatures probably occurred historically in larger rivers (now mostly extirpated), and warm-water populations occur currently in some geothermally heated streams, though the fishes there may rely on thermal refugia (see Gresswell 1995). Resident populations generally spawn within their home range in lotic systems; may migrate but do not enter tributary streams; after emergence, fry may move upstream or downstream or remain near the redd (Gresswell 1995). Fluvial populations migrate from larger streams into tributaries to spawn; juveniles may emigrate as fry or spend 1-3 years in natal tributaries before returning to the mainstem (Gresswell 1995). Adfluvial populations live in lakes and ascend inlets or descend outlets to spawn; young may move into the lake shortly after emergence, or they may remain in their natal stream for one or more years if the habitat is suitable; spawners may remain in breeding habitat about 1-3 weeks or up to many months (Gresswell 1995). Fry generally use areas of low water velocity. In Yellowstone Lake, juveniles apparently are primarily pelagic.
Spawning streams generally are perennial with groundwater and snow-fed water sources and a gradient usually less than 3%; some spawning in intermittent streams does occur (Gresswell 1995). Spawning sites generally have gravel 12-85 mm in diameter, a water depth of about 9-30 cm, and a water velocity of 14-73 cm/sec (see Gresswell 1995). Spawns usually in the natal stream. See Gresswell (1995) for further details on habitat.
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.
Resident, or migrates short distances between breeding and nonbreeding habitats.
Comments: Appears to feed on fishes more so than does the westslope cutthroat (Behnke 1992). Highly piscivorous in some lacustrine habitats but feeds opportunistically on zooplankton, larger crustaceans, and aquatic insects in other situations, including some lakes (Gresswell 1995).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 80
Comments: There are about 133 core conservation (nonintrogressed) populations (USFWS 2006).
10,000 to >1,000,000 individuals
Predators include white pelicans, bald eagles, and grizzly bears. Introduced longnose sucker, redside shiner, and lake chub have had no detectable effect on the cutthroat population in Yellowstone Lake (see Behnke 1992 and Gresswell 1995). In Yellowstone Lake, tapeworm infection is common and there is evidence that human infection from eating infected fishes is possible (see Gresswell  for further information on parasites and diseases).
Life History and Behavior
Comments: Active feeding may occur at water temperatures as low as 0-4 C (Gresswell 1995).
Spawner abundance generally increases as water temperature rises and discharge decreases from spring runoff peak; spawns generally between March and August, with migrations beginning when temperatures approach 5 C and peaking at 10-20 C (varies with location) (see Gresswell 1995). Spawning often peaks in June in many areas. Eggs hatch generally in 25-49 days, and juveniles emerge from the gravel 2 weeks later (see Gresswell 1995). Age of spawners varies geographically; youngest spawners generally are 3-5 years old. Average age of spawners in a Yellowstone Lake tributary increased from 3.9 years to 5.6 years after mortality due to angling was reduced; the increase was due mainly to an increase in the number of repeat spawners (see Behnke 1992). Growth rate generally increases as elevation decreases (Gresswell 1995). In different populations, maximum age varies from about 8 to 11 years. Repeat spawning, in consecutive or alternate years, is common, though it may be infrequent where angler harvest is relatively high (Gresswell 1995).
National NatureServe Conservation Status
Rounded National Status Rank: N3 - Vulnerable
NatureServe Conservation Status
Rounded Global Status Rank: T3 - Vulnerable
Reasons: In determining that petitioned listing of Yellowstone cutthroat trout is not warranted, USFWS (2006) reported the following: At least 195 extant conservation populations of this subspecies collectively occupy 10,220 km (6,352 mi) of stream and lake habitat in Idaho, Montana, Wyoming, Utah, and Nevada. Those 195 populations are distributed among 35 component watersheds in the Snake and Yellowstone River basins. Of those 195 conservation populations, about 133 were considered likely to qualify as potential ''core conservation populations'' comprising nonintrogressed Yellowstone cutthroat trout (99 percent genetic purity standard). If, after further genetic testing the existence of approximately 133 core conservation populations is verified, then those populations would include about 3,009 km (1,870 mi) of habitat encompassing about 29 percent of the existing range of conservation populations of Yellowstone cutthroat trout. Although the distribution of Yellowstone cutthroat trout has been reduced from historical levels and existing populations face threats in several areas of the historic range, USFWS found that the magnitude and imminence of those threats do not compromise the continued existence of the subspecies within the foreseeable future (defined as 20-30 years). Many former threats to Yellowstone cutthroat trout, such as those posed by excessive harvest by anglers or the ongoing stocking of nonnative fishes, are no longer factors that threaten the continued existence of Yellowstone cutthroat trout.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Recent trends appear to be stable or upward, with a few notable exceptions (i.e., Yellowstone Lake, Teton River) (USFWS 2006).
Global Long Term Trend: Decline of 30-70%
Comments: Distribution has declined perhaps by more than 50% over the past 200 years; much of that loss is believed to have occurred in the late 19th and early 20th century (see USFWS 2006).
Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable
Comments: Threats include dewatering, water diversion, chemical pollution, siltation, barriers to movement, excessive angler harvest, genetic introgression, and introduced fishes, all resulting primarily from human activities (see Gresswell  for further details). Habitat degradation is continuing "at an alarming rate" (Gresswell 1995). In Yellowstone River tributaries downstream from Yellowstone National Park, native populations have been largely replaced by brook, brown, and rainbow trout and by hybrid rainbow/cutthroat populations (Behnke 1992, Gresswell 1995). Coexistence with brown and brook trouts may be possible in some areas if habitat is not degraded and angler harvest is not extreme (see Gresswell 1995). Differences in spawning season have prevented hybridization with rainbow trout in some areas (Gresswell 1995). Introduced lake trout have caused drastic declines in cutthroat populations in some areas but not in others; impact is through competition and/or predation; the recent and unauthorized introduction of lake trout in Yellowstone Lake is predicted to result in a decline of 90% or more in the cutthroat trout population in 20-100 years if the lake trout population is not controlled (Kaeding et al. 1996). Behnke (2002) reported that the impact of lake trout on native cutthroat trout would be devastating without the ongoing program to remove lake trout from Yellowstone Lake. Angler wading may result in high mortality of eggs and pre-emergent fry (see Gresswell 1995). The non-native parasite Myxoblus cerebralis, which causes whirling disease, recently was found in some Yellowstone Lake cutthroat trout (Behnke 2002); infection level was low, and so far whirling disease has not caused a significant decline in abundance.
Restoration Potential: Restoration can be difficult and expensive once native cutthroat populations have been replaced by and/or have hybridized with non-native salmonids.
Management Requirements: Primary management concerns include preventing the establishment of non-native fishes in waters occupied by native cutthroat trout. Once cutthroat trout have been replaced by another salmonid, the situation generally is irreversible without human intervention (Moyle and Vondracek, cited by Gresswell 1995). Elimination/curtailment of trout stocking in streams by state agencies has been helpful in maintaining the genetic integrity of Yellowstone cutthroat trout populations. In the 1980s, chemical treatment of Arnica Creek, a tributary of Yellowstone Lake, apparently was successful in eliminating illegally introduced brook trout (see Behnke 1992), but such removals are expensive and difficult to achieve (Gresswell 1995). Genetic restoration of introgressed populations is needed in some areas.
Introduced lake trout need to be controlled in Yellowstone Lake. Gillnetting or some combination of gillnetting and trapping may be the most effective management actions (Kaeding et al. 1996).
Habitat protection is important, as is enhancement, such as modifying culverts to facilitate fish movement (see Gresswell  for suggestions and references). Other needed management actions include reductions in water diversions, improved riparian management, continued use of angling restrictions (Gresswell 1995).
Management Research Needs: Identify large-scale habitat factors that influence distribution, dispersal, and recolonization so that the effects of current land-use activites and anticipated global climate change can be evaluated (Gresswell 1995). Determine whether life history variation has a genetic basis (Gresswell 1995). Examine life history characteristics in relatively undisturbed populations (Gresswell 1995). Assess the indirect effects of angling, such as redd trampling and bank erosion (Gresswell 1995).
Needs: Protect populations from introductions of non-native salmonids and from excessive harvest. Protect populations in various habitats throughout the range, including multiple representatives of all life history forms.
Relevance to Humans and Ecosystems
Comments: A popular game fish; has been widely stocked in much of the West; different stocks vary in their productivity when stocked in non-native waters (Behnke 1992).
Yellowstone cutthroat trout
The Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) is a subspecies of the cutthroat trout (Oncorhynchus clarki) and is a freshwater fish in the salmon family (family Salmonidae) of the order Salmoniformes. Native only to a few U.S. states, their original range was upstream of Shoshone Falls on the Snake River and tributaries in Wyoming, also across the Continental Divide in Yellowstone Lake and in the Yellowstone River as well as its tributaries downstream to the Tongue River in Montana. The species is also found in Idaho, Utah and Nevada.
The Yellowstone cutthroat trout is a prized game fish, with fly fishing the most popular angling method, since the subspecies feeds primarily on insects as adults, unlike introduced brown trout which are more piscivorous. Most varieties of cutthroat trout are less wary and selective than other trout species, thus angler success rates are higher.
Yellowstone cutthroat can be distinguished from other cutthroat subspecies by their larger black spots, clustered towards the tail, and by their gray, gold, or copper hues. Spawning males, especially, typically wear golden brown colors. All cutthroats can be differentiated from rainbow trout by red, pink, or orange marking beneath the jaw that give the species its name.
Depending on habitat, Yellowstone cutthroat can range from six to twenty-six inches as adults, with six to ten inches common in high-elevation, high-gradient tributary streams and the largest fish found only in lakes or in spawning tributaries that feed lakes or emerge from them, such as the Yellowstone River in Hayden Valley in Yellowstone National Park. As a general rule, cutthroat in streams and small ponds run from ten to eighteen inches as adults, with a weight of one half to two pounds. Before habitat destruction, the threats presented by introduced species, and overfishing, they could run much larger, with fish over thirty inches reported, especially in the strain present in Heart Lake in the southeastern portion of Yellowstone National Park.
Regardless of habitat, all Yellowstone cutthroat trout require flowing water to spawn successfully. Ponds and lakes must have inlet or outlet streams for cutthroat for self-sustaining populations. Some fish are stocked in otherwise suitable lakes in the Beartooth Mountains and elsewhere to provide angling opportunities that otherwise would not be available.
Their range has been reduced by overfishing and habitat destruction due to mining, grazing, and logging, and population densities have been reduced by competition with nonnative brook, brown and rainbow trout since these were introduced in the late 19th and early 20th centuries. However the most serious current threats to the subspecies are interbreeding with introduced rainbow trout (resulting in cutbows) in the Greater Yellowstone Ecosystem, the presence of lake trout in Yellowstone and Heart lakes in Yellowstone National Park which prey upon cutthroat trout to fifteen inches in length, and several outbreaks of whirling disease in major spawning tributaries.
Although lake trout were established in Shoshone and Lewis 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 illegal introductions.
Occasional drought in the Yellowstone area makes several spawning tributaries run dry in late summer, preventing cutthroat fry from migrating to Yellowstone Lake and making them easy prey for predators such as gulls, pelicans, and others. These threats have significantly reduced cutthroat populations in Yellowstone Lake and adjacent parts of the Yellowstone River. Currently, the strongest populations of cutthroat are to be found in the Grand and Black Canyons of the Yellowstone River and in the Yellowstone's major tributary in Yellowstone Park, the Lamar River and its tributaries. Attempts as recently as 2004 by environmentalists to have the U.S. Fish and Wildlife Service place the subspecies on the list of Endangered Species was not approved by the agency, citing evidence that major efforts are already underway to ensure the continued existence of this subspecies. All Yellowstone cutthroat trout caught within Yellowstone National Park must be released. Populations outside the national park are subject varying regulations depending on the location of the stream or waterway.
- "Montana Field Guide-Yellowstone Cutthroat Trout". Montana Department of Fish, Wildlife and Parks. Retrieved 2013-11-16.
- Gresswell, Robert E. (June 30, 2009). "Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri): A Technical Conservation Assessment" (pdf). U.S. Geological Survey. Retrieved 2011-11-04.
- "The Yellowstone Lake Crisis: Confronting a Lake Trout Invasion" (PDF). National Park Service. 1995. Retrieved 2007-03-19.
- Kendall, W. C. (1921). The Fishes of the Yellowstone National Park. Washington D.C.: Department of Commerce, Bureau of Fisheries. pp. 22–23.
Names and Taxonomy
Comments: Hybrids between this subspecies and rainbow trout may not be detectable using morphological/meristic traits alone (e.g., see Kruse et al. 1996). Forbes and Allendorf (1991) found that mitochondrial genotypes had no detectable effects on meristic traits in interbreeding trouts of the subspecies LEWISI (westslope) and BOUVIERI (Yellowstone), which exhibit substantial genetic divergence.
Introductions have led to hybridization with westslope cutthroat trout and rainbow trout.
Management actions in the first half of the 1900s, largely in the Yellowstone Lake system, led to the potential mixing of up to 68 historically distinct genetic entities (Gresswell 1995).
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