Oncorhynchus clarkii
cutthroat trout

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). (Trotter, 1987)

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. (Behnke, 1992)

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. (Behnke, 1992; Trotter, 1987; Willers, 1991)

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. (Trotter, 1987; Willers, 1991)

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). (Behnke, 1992)

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). (Behnke, 1992; Elliott, 2005)

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). (Behnke, 1992)

Cutthroat trout are solitary and sedentary, rarely moving or interacting unless it is to acquire food or to mate. When they do move, they propel themselves through the water by moving the latter half of their bodies (subcarangiforms). Some populations migrate from their natal streams to the ocean, while others migrate to lakes and ponds. (Behnke, 1992)

Home Range

Juvenile cutthroat establish their home ranges when they are about two years old (Behnke, 1992). These home ranges are relatively small. Sea run cutthroat rarely travel more than 60 km from their natal streams (Behnke, 1992). (Behnke, 1992)

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. (Elliott, 2005)

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). (Behnke, 1992; Morrow, 1980)

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). (Behnke, 1992; Elliott, 2005)

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. (Elliott, 2005; Morrow, 1980)

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. (Coad, 1995; Trotter, 1987)

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. (Behnke, 1992; Trotter, 1987)