Westslope cutthroat trout

Westslope cutthroat trout
Westslope cutthroat trout
Westslope cutthroat trout
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Oncorhynchus
Species: O. clarki
Subspecies: O. c. lewisi
Trinomial name
Oncorhynchus clarki lewisi
( Pratt & Graham, 1884)

The westslope cutthroat trout (Oncorhynchus clarkii lewisi), also known as the blackspotted cutthroat, is a subspecies of the cutthroat trout (Oncorhynchus clarkii) and is a freshwater fish in the salmon family (family Salmonidae) of order Salmoniformes.[1] The cutthroat is the Montana state fish.[2] This subspecies is a species of concern.[3]



Westslopes are native in northern Idaho's and British Columbia's upper Columbia system and northern tributaries of the Snake River, but not the Snake River's main stem to the south. Across the Continental Divide in Alberta and Montana, westslopes are native to the upper Missouri River, Milk River and North Saskatchewan River, but not the Yellowstone River to the south. Instead, Yellowstone cutthroat trout are found south of westslopes on both sides of the Continental Divide. However there is a remnant population of westslopes in Oregon. Small populations persist in upper tributaries of the John Day River in the Strawberry Mountains.


The fish has teeth under its tongue, on the roof of the mouth, and in the front of the mouth. Westslope cutthroat are common in both headwaters lake and stream environments. They feed mainly on insects and zooplankton. The average length of the fish is about 8-12 inches (30 cm) and rarely exceeds 18 inches (46 cm). The skin has small dark freckle-like spots clustered towards the tail, and is mostly orange-hued. They can be distinguished from rainbow trout by the red, pink, or orange marking beneath the jaw (whence the name "cutthroat").


The westslope cutthroat trout is an indicator species of the health of the entire ecosystem of its habitat. It requires pure, cold water for survival, secure connected habitat (tributaries and main stems), and protection from introduced nonnative fish. When these requirements are not met, the number of individuals plummets. The subspecies is also in danger of hybridization and may in fact disappear from the Northern Rockies without a region wide, long-term effective protection and recovery effort.[citation needed]

Pure westslope cutthroat are extirpated throughout most of their historic range, and existing populations are in imminent danger from land-use activities and hybridization with introduced rainbow trout (resulting in cutbows)[4] and Yellowstone cutthroat trout. Even the strongest populations in Glacier National Park and the Flathead Basin of Montana are in serious decline. Reasons for the critical condition of the subspecies include habitat destruction from logging, road building, grazing, mining, urban development, agriculture and dams, introduction of non-native hatchery strains, competition and hybridization from introduced non-native fish species.[citation needed]

The Northern Rockies conservation community’s campaign to protect and recover the westslope cutthroat trout involves a broad coalition of scientists, conservationists, American heritage historians, the sportfishing community, the arts and humanities community, representatives of Native American and ranching communities, and politicians.[citation needed]

Origin of scientific name

The westslope cutthroat trout has the trinomial name Oncorhynchus clarkii lewisi, in honor of Meriwether Lewis and William Clark who led the Lewis and Clark Expedition of 1804–1806. The expedition discovered the subspecies at Great Falls of the Missouri in what is now Montana. One of Lewis and Clark’s missions was to bring back word and samples of the flora and fauna encountered during the expedition.


  1. ^ "Montana Field Guide-Westslope Cutthroat". Montana Department of Fish, Wildlife and Parks. http://fieldguide.mt.gov/detail_AFCHA02088.aspx. Retrieved 2010-12-11. 
  2. ^ 1-1-507. State fish, Montana Code, accessed 23 April 2009.
  3. ^ Species of concern are native taxa that are at-risk due to declining population trends, threats to their habitats, restricted distribution, and/or other factors. Designation as a Montana species of concern or potential species of concern is based on the Montana Status Rank, and is not a statutory or regulatory classification. Rather, these designations provide information that helps resource managers make proactive decisions regarding species conservation and data collection priorities. See the latest pecies of concern reports for more detailed explanations and assessment criteria. "Montana Field Guide-Species of Concern". http://fieldguide.mt.gov/statusCodes.aspx#soc. Retrieved 2010-12-07. 
  4. ^ Hitt, N.P., et al. (2003) Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and nonnative rainbow trout, Oncorhynchus mykiss. Can. J. Fish. Aquat. Sci. 60, 1440-1451. doi:10.1139/F03-125

External links

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