Oncorhynchus clarkii

Prefers relatively small streams, with gravel bottoms and gentle gradients. Spawning adults migrate from the sea into streams to spawn (Ref. 27547). The young fish usually stay in the stream for a year or two before entering the sea, but some populations never got to sea at all. In rare cases, some individuals of sea-going populations, may remain in fresh water for as long as eight years (Ref. 28866, 28869). Feeds on small fishes, crustaceans, and insects (Ref. 4925). The flesh is orange-red and of excellent flavor (Ref. 27547). Utilized fresh and eaten fried, broiled, and baked (Ref. 9988). This species does not compete well with other fish, tends to hybridize, and is unable to withstand fishing pressure = depletion of stocks.

Cutthroat trout, Oncorhynchus clarkii, are widely distributed along the western coast of North America. They can be found as far north as Alaska’s Prince William Sound and as far south as California’s Eel River (Willers, 1991). Their range also extends inland where they can be found on most waterways with linkages to their western range along the Pacific coast (Trotter, 1987).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Anadromous forms: Pacific Coast drainages from Eel River, California, north to Prince William Sound, Alaska, generally not more than 160 km inland; non-migrating fish also occur through this range. Allopatric inland forms: Rocky Mountains in Hudson Bay basin, Mississippi River basin, Great Basin (including Lahontan, Bonneville, and Alvord basins), and Pacific basin from southern Alberta south through California to the Rio Grande drainage, New Mexico, and east to Colorado and Montana (Lee et al. 1980, Page and Burr 1991). The greatest abundance of pure interior cutthroat trout occurs in Yellowstone Lake and the Yellowstone River drainage above the falls in Yellowstone National Park (Behnke 1992). Widely stocked in and out of the original range. Established in Laurentian lakes, Quebec. However, rarely has become naturalized much beyond the original distribution (Behnke 1992). Occurrence in high elevation headwater lakes is due primarily to introductions (formerly excluded by falls) (Behnke 1992). Locally common (Page and Burr 1991).

Eastern North Pacific, introduced elsewhere.

Eastern Pacific: northern parts of Prince William Sound, Alaska, south to the Eel River in northern California, USA and is found in most streams emptying into the Pacific. Widely introduced into various streams and lakes within its natural range, as well as into a few lakes in eastern North America. In some streams it may be the most numerous sport fish present, while other streams support only small populations. At least 14 subspecies have been historically recognized (Ref. 5723).

There are roughly ten subspecies of cutthroat trout described by Behnke (1992). They have the same morphology, but their coloration and spotting vary. Coastal cutthroat trout, O. c. clarki, are silvery to brassy in coloration with yellowish and irregular shaped spots. West slope cutthroat trout, O. c. lewisi, are silver in coloration with a yellowish tint, but can sometimes be bright yellow, orange, or red. Their spots are similar to those of coastal cutthroat except they do not extend below the lateral line. Yellowstone cutthroat trout, O. c. bouvieri, are yellowish brown, silver, or brass in coloration with round spots evenly distributed over the body. Lahontan cutthroat trout, O. c. henshawi, are dull in coloration with large round spots evenly distributed over the entire body. Paiute cutthroat trout, O. c. seleniris, closely resemble the Lahontan cutthroat with a dull coloration, but unlike the Lahontan, Paiute cutthroat lack spots. Bonneville cutthroat trout, O. c. utah, have the same coloration and spotting as Yellowstone cutthroat with one exception, the spots are larger on Bonneville cutthroat. Colorado river cutthroat trout, O. c. pleuriticus, are strong red in coloration along the lateral line and their lower sides are colored yellow. They have spots but they vary by individual. Greenback cutthroat trout, O. c. stomias, are similar to Colorado River cutthroat in coloration, however greenback cutthroat trout have larger spots. Rio Grande cutthroat trout, O. c. virginalis, are similar to greenback cutthroat in both coloration and spotting. Rio Grande cutthroat have, in addition, close spotting on the caudal peduncle. Yellowfin cutthroat trout, O. c. macdonaldi, have the coloration of the greenback but have a silvery tint and their spots are irregular.

The subspecies all share the following characteristics: red slash marks just below their gill covers on the lower jaws (Trotter, 1987) and a scale count above the lateral line of more than 150 (Willers, 1991). Where cutthroat and rainbow trout ranges overlap, the two species can be distinguished by the presence of basibranchial teeth, or teeth on the base of the tongue (Trotter, 1987). Cutthroat trout posses them, while rainbow trout do not.

The average length for a cutthroat trout is between 20 and 40 cm while the average weight is between 2 and 4 kg. Surprisingly, the environment a cutthroat trout occupies may be the limiting factor on how big a cutthroat can get, with genetic control only being a factor in an optimal environment (Behnke, 1993).

Range mass: 19 (high) kg.

Average mass: 2-4 kg.

Range length: 99 (high) cm.

Average length: 20-40 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: sexes alike

Dorsal spines (total): 0; Dorsal soft rays (total): 8 - 11; Analspines: 0; Analsoft rays: 8 - 12

Length: 99 cm

99.0 cm TL (male/unsexed; (Ref. 12204)); max. published weight: 18.6 kg (Ref. 9988); max. reported age: 10 years (Ref. 3221)

Color is variable. Generally dark green to greenish-blue on back, olive-green on upper flank, silvery on lower flank and belly; flanks spots below lateral line are more numerous anteriorly; irregular spots on dorsal, adipose and caudal fins and the anal, pectoral and pelvic fin bases; gill covers are pinkish. Those found at sea or recent migrants to freshwater are silvery with a bluish back, yellowish lower flanks and fins, and sparse spots.

Because O. clarkii is such a widespread species it occupies many different habitats. Cutthroat trout habitats range from coastal marine to freshwater rivers and streams with gravel substrates (Behnke, 1992). The diversity in habitat also leads to a diversity in the elevations in which the species can be found. They occur from mountainous streams in the Cascade, Rocky, and Sierra Nevada mountain ranges to the ocean.

Habitat Regions: temperate ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; lakes and ponds; rivers and streams; coastal ; brackish water

Other Habitat Features: estuarine

Habitat Type: Freshwater

Comments: Estuaries or marine waters near the coast, small rivers, gravelly streams, and isolated mountain lakes.

Spawning usually occurs in gravel stream riffles where the female digs a nest (redd) in the gravel.

demersal; anadromous (Ref. 27547); freshwater; brackish; marine; depth range 0 - 200 m (Ref. 50610)

Depth range based on 5 specimens in 2 taxa.

Environmental ranges
  Depth range (m): 0.385 - 2.5

Graphical representation

Depth range (m): 0.385 - 2.5
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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: No. No 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: Yes. At least some populations of this species make annual migrations of over 200 km.

In general, anadromous (sea going) and lake cutthroat trout make extensive spawning migrations; nonmigratory stream- dwelling cutthroats are often quite sedentary (Moyle 1976).

In summer and fall, radio-tagged cutthroat trout in Strawberry Reservoir in Utah had single-month home ranges that were usually about 3-4 km in maximum length (Baldwin et al. 2002).

In the Blackfoot River drainage, Montana, radio-tagged westslope cutthroat trout moved 3-72 km (mean 31 km) to access spawning tributaries (Schmetterling 2001).

Anadromous. Fish that ascend rivers to spawn, as salmon and hilsa do. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.

A cutthroat trout's diet changes as they progress through the life stages. As fry they feed on small crustaceans and algae. As they progress into fingerlings they feed on small insects, and crustaceans. Juveniles and adults become opportunistic feeders, eating almost any prey item in their environment (Behnke, 1992). They are known to eat other fishes, crustaceans, and insects (Morrow, 1980).

Animal Foods: amphibians; fish; eggs; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic or marine worms

Plant Foods: algae

Primary Diet: carnivore (Piscivore , Insectivore , Eats non-insect arthropods)

Prefers relatively small streams, with gravel bottoms and gentle gradients. Spawning adults migrate from the sea into streams to spawn (Ref. 27547). The young fish usually stay in the stream for a year or two before entering the sea, but some populations never got to sea at all. In rare cases, some individuals of sea-going populations, may remain in fresh water for as long as eight years (Ref. 28866, 28869). Feeds on small fishes, crustaceans, and insects (Ref. 4925).

Comments: Opportunistic. Inland cutthroats feed primarily on insects (aquatic and terrestrial); often feeds in and especially downstream from riffle areas; some large individuals feed mostly on fishes; also eats zooplankton and crustaceans. Coastal cutthroats feed in salt water on crustaceans and fishes; in streams, they eat aquatic insects and crustaceans, also frogs, earthworms, fishes, fish eggs, salamanders, etc.

Cutthroat trout are prey for larger fish as fry or fingerlings. As adults they become predators. When sea run cutthroat die in their natal streams, they release nutrients they acquired in the ocean as they decompose.

Young cutthroat trout are preyed on by larger fish and large, wading birds. Adult trout are preyed on by large predators, such as bears. There are several life history adaptations they posses that increases their chances of survival. Cutthroat often select spawning grounds that are isolated from spawning grounds used by other fish (Elliott, 2005). Juveniles are also sit and wait predators darting out to capture food, minimizing the time during feeding that they are susceptible to predation (Elliott, 2005). Fry and fingerling cutthroat have parmarks on their sides, which camouflage them from possible predators (Behnke, 1992).

Known Predators:

• steelhead or rainbow trout (Oncorhynchus mykiss)
• coho salmon (Oncorhynchus kisutch)
• herons (Ardea)
• bears (Ursus)

Anti-predator Adaptations: cryptic

Enteric Redmouth Disease. Bacterial diseases

In streams, cutthroats defend feeding territories. Population densities are regulated mostly by stream size and morphology, overwintering habitat, stream productivity, and summer cover for predator avoidance (New Mexico, Sublette et al. 1990).

Cutthroat trout are visual predators. They depend on a keen sense of sight to locate and consume their prey. Male cutthroat trout use body signals when trying to court females for spawning (Elliott, 2005). It has been demonstrated that trout use chemical cues to re-locate natal streams for spawning.

Communication Channels: tactile

Perception Channels: visual ; tactile ; chemical

Young cutthroat trout emerge from their eggs after two months (Elliot, 2005). Once they hatch they mature, spawn, then die. Cutthroat trout that migrate to the sea develop for up to four years in their natal stream, then migrate into the ocean only to return 2 to 3 months later to spawn (Behnke, 1992).

Development - Life Cycle: indeterminate growth

Spawning occurs both daytime and nighttime. The female selects a site and builds a redd while the male courts her and drives away other males. Upon completion of the redd, the female settles into the pitt, immediately followed by the male. The pair releases eggs and sperm simultaneously and the eggs fall into the spaces between the gravel. The female then moves to the upstream edge of the redd and resumes digging, thereby covering the eggs. When completely covered, the female may use the new redd to spawn once more or she may look for another spot and repeat the entire process. Both males and females spawn with one or more members of the opposite sex (Ref. 12204, 27547). Reproductive strategy: synchronous ovarian organization, determinate fecundity (Ref. 51846).

Cutthroat trout are not an exceptionally long lived fish. Depending on the subspecies a mature trout may live anywhere from 6-8 years (Behnke, 1992).

Typical lifespan
Status: wild: 6 to 8 years.

Maximum longevity: 10 years (wild)

Oncorhynchus clarkii are stream spawners like other fishes belonging to the Salmonidae family (Vinyard, 2004). During a spawning event a female will dig a redd, a nest in gravel (Vinyard, 2004). Males court females by nudging them with their noses and quivering (Elliott, 2005). The female lays her eggs in the redd and the male swims over and deposits his sperm.

Mating System: polygynous

Sea run cutthroat trout migrate from their marine environments to their natal streams to spawn from February to early June (Elliott, 2005). Likewise freshwater cutthroat migrate from larger rivers and lakes to smaller streams to spawn (Behnke, 1992). Females and males reach sexual maturity at around 6 years of age. Both river and sea run cutthroat can spawn several times; however, the probability of dieing during a spawning event increases with age (Behnke, 1992). A single spawning event produces 1000-2000 eggs, which, if fertilized, hatch just after 2 months of gestation (Elliott, 2005).

Breeding interval: Breeding can occur once or twice in the lifetime of a cutthroat trout.

Breeding season: Spawning occurs from spring to early summer.

Range number of offspring: 1000 to 2000.

Range gestation period: 1 to 2 months.

Range age at sexual or reproductive maturity (female): 5 to 7 years.

Range age at sexual or reproductive maturity (male): 5 to 7 years.

Key Reproductive Features: semelparous ; iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning

Prior to fertilizationm female cutthroat trout dig a redd, a nest in gravel (Vinyard, 2004). Once eggs are deposited and become fertilized, the female covers them and may defend the redd for some time (Vinyard, 2004). After a short period of guarding, the female departs, leaving the eggs to hatch on their own. Once hatched, the parent cutthroat shows no type of parental investment.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female)

Inland populations spawn March-early July, depending on location and conditions; coastal populations usually spawn February-May (Moyle 1976, Scott and Crossman 1973). Eggs hatch in 6-8 weeks. Females are sexually mature at 3-4 years, males at 2-3 years (Sigler et al. 1983). Females spawn up to five times during their lifetime. See Stearley (1992) for a discussion of the historical ecology and life history evolution of Pacific salmons and trouts (ONCORHYNCHUS).

Currently, cutthroat trout are not on the IUCN red list. There are some factors that may put these fish on the list soon. Through stocking streams, rivers, and ponds with rainbow trout throughout the west we may be putting native cutthroat trout in harms way. Cutthroat trout and rainbow trout readily mate, creating hybrids that are themselves able to mate (Behnke, 1992). Cutthroat trout are also poor competitors, out-competed by all other trout species (Trotter, 1987). If we continue to introduce non-native trout to cutthroat streams and rivers, cutthroat trout may be eliminated. Another factor affecting cutthroat trout is habitat loss. Logging and excessive agriculture cause sedimentation in trout streams, making them inhabitable and unsuitable for reproduction (Behnke, 1992). Three subspecies of Oncorhynchus clarkii are threatened throughout the western states.

US Federal List: threatened

CITES: no special status

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Comments: Declines have occurred primarily because of habitat degradation/destruction and the effects of introduced trout species. The greatest threat is introgressive hybridization among subspecies and with rainbow trout/steelhead (Allendorf and Leary 1988). This is a major concern in inland populations, but hybridization may also occur in coastal populations (Baker et al. 2002).

Subspecies macdonaldi (yellowfin cutthroat), formerly in Twin Lakes, Lake County, Colorado, is extinct apparently due to introgressive hybridization with rainbow trout and competition from deep-water lake trout (Miller et al. 1989).

An unnamed subspecies from Alvord Basin, southeastern Oregon (Trout Creek) and northwestern Nevada (Virgin Creek), is extinct as a pure form, apparently due to hybridization and introgression with introduced rainbow trout; no genetically pure populations are known (Miller et al. 1989).

Behnke (1992) described instances in which cutthroat trout were quickly replaced by brook trout, both with and without associated habitat disturbance.

Sea-run cutthroat underwent a major decline in the 1970s and 1980s, evidently due to habitat damage and overfishing; for populations above Bonneville Dam, dam passage takes a toll; in many areas, native stocks have been eroded by introductions of hatchery stock (Nehlsen et al. 1991).

See also records for the various subspecies.

Not Evaluated

Preserve Selection and Design Considerations: Where non-native trout pose a threat to native cutthroat trout populations and restoration, isolated headwater reaches managed for cutthroat trout should be as large and diverse as possible, and improvements may be needed to ensure that habitat requirements are met (Novinger and Rahel 2003).

Management Requirements: Though most high-elevation populations have been exposed to hybridization and are not pure native trout, Behnke (1992) noted that they do maintain the appearance of native trout and recommended that they be recognized and managed as such.

See Nehlsen et al. (1991) for general protection and management recommendations for anadromous salmonids.

Allendorf et al. (1997) proposed criteria for prioritizing Pacific salmon stocks for conservation; data limitations introduce subjectivity into the process, so expert judgment and peer review should be incorporated into the process.

See also files for subspecies.

There are no negative impacts of cutthroat trout on humans.

Cutthroat trout are an important sport fish throughout northwestern North America (Trotter, 1987; Coad, 1995). They are also indicative of healthy ecosystems.

Positive Impacts: food

fisheries: commercial; aquaculture: commercial; gamefish: yes; aquarium: public aquariums