Westslope cutthroat trout
Westslope cutthroat trout
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Oncorhynchus
Species:
O. clarkii
Subspecies:
O. c. lewisi
Trinomial name
Oncorhynchus clarkii lewisi
(G. Suckley, 1856)
The historic distribution of westslope cutthroat trout in the United States (modified from Behnke 1992). The large region consists primarily of the upper Columbia River and upper Missouri River basins; some waters in the eastern part of this region may not have been occupied historically (MTFWP, in litt. 1998). Also shown are the Lake Chelan and Methow River drainages in Washington and the John Day River drainage in Oregon.[1]
Synonyms[2]
  • Salmo mykiss lewisi (Jordan and Evermann, 1896)
  • Salmo clarkii lewisi (Jordan and Evermann, 1898)
  • Salar lewisi (Suckley, 1856)
  • Salmo clarkii alpestris (Drymond, 1931)

The westslope cutthroat trout (Oncorhynchus clarkii lewisi), also known as the black-spotted trout, common cutthroat trout and red-throated trout is a subspecies of the cutthroat trout (Oncorhynchus clarkii) and is a freshwater fish in the salmon family (family Salmonidae) of order Salmoniformes.[3] The cutthroat is the Montana state fish.[4] This subspecies is a species of concern in its Montana[5] and British Columbia[6] ranges and is considered threatened in its native range in Alberta.[7]

Taxonomy

The scientific name of the westslope cutthroat trout is Oncorhynchus clarkii lewisi, as it was first described in the journals of explorer William Clark from specimens obtained during the Lewis and Clark Expedition from the Missouri River near Great Falls, Montana. Cutthroat trout were given the name Salmo clarki in honor of William Clark, who co-led the expedition of 1804–1806.[8] One of Lewis and Clark's missions was to describe the flora and fauna encountered during the expedition. The type specimen of S. clarki was described by naturalist John Richardson in 1836 from a tributary of the lower Columbia River, identified as the "Katpootl",[8] which was perhaps the Lewis River as there was a Multnomah village of similar name at the confluence. This type specimen was most likely the coastal cutthroat subspecies.[9] In 1853, naturalist George Suckley while working for the Pacific Railroad Survey led by Isaac Stevens collected specimens of westslope cutthroat trout by fly fishing below the Great Falls on the Missouri River. In 1856, he described the trout as Salar lewisi to honor explorer Meriwether Lewis.[10] In David Starr Jordan and Barton Warren Evermann's A Check-list of the Fishes and Fishlike Vertebrates of North and Middle America (1896), the name Salmo mykiss lewisi was given to Yellowstone trout or cut-throat trout and included a reference to specimens collected from the Missouri River by George Suckley.[11] In 1898, Jordan and Evermann changed the name of cutthroat trout to Salmo clarki.[12] Salmo clarki lewisi persisted as the subspecies name for both the Yellowstone cutthroat and westslope cutthroat trout until 1971 when fisheries biologist Robert J. Behnke gave the name Salmo clarki bouvieri to the Yellowstone cutthroat with Salmo clarki lewisi reserved for the westslope cutthroat trout.[9]

In 1989, morphological and genetic studies indicated trout of the Pacific basin were genetically closer to Pacific salmon (Oncorhynchus species) than to the Salmos–brown trout (S. trutta) or Atlantic salmon (S. salar) of the Atlantic basin.[13] Thus, in 1989, taxonomic authorities moved the rainbow, cutthroat and other Pacific basin trout into the genus Oncorhynchus.[14]

Description

A Westslope cutthroat in the Flathead River near Missoula, Montana

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 (hence the name "cutthroat").

Range

Westslope cutthroat trout are native in northern Idaho's and British Columbia's upper Columbia River system and northern tributaries of the Snake River, but not the Snake River's main stem to the south. East of the Continental Divide in Alberta and Montana, westslope cutthroat trout are native to the upper Missouri, Milk and North Saskatchewan rivers, but not the Yellowstone River to the south. In Montana, the historic range extended east to the mouth of the Judith River and south into the Madison, Gallatin and Jefferson river systems.[10] Isolated populations of westslope cutthroat trout exist in upper tributaries of the John Day River in the Strawberry Mountains of Oregon[15] and Columbia River tributaries along the eastern side of the Cascade range in Washington. Isolated populations exist in the Fraser River basin in British Columbia.[10] Existing populations of genetically pure westslope cutthroat trout exist in less than three percent of its historic range.

Life cycle

Westslope cutthroat trout reflect three life strategies—adfluvial, fluvial, or stream resident. Adfluvial fish live in the large lakes in the upper Columbia River drainage and spawn in lake tributaries. Fluvial fish live in medium to large rivers but migrate to tributaries for spawning. Most adults return to the river or lake after spawning. Stream resident fish complete their entire life in tributaries. All three forms occur in most basins.[16]

Conservation

Genetically pure westslope cutthroat trout have been extirpated throughout most of their historic range due to habitat loss and introduction of non-native species. Remaining populations survive in isolated populations, mostly in headwater streams above natural downstream barriers. The introduction of rainbow and brown trout into Missouri River tributaries eliminated the westslope cutthroat trout from most of its eastern range in Montana. Introductions of non-native kokanee salmon (Oncorhynchus nerka), lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) into Flathead Lake and the Flathead River system caused drastic declines in westslope cutthroat trout populations.[10] Existing populations are in imminent danger from land-use activities and hybridization with introduced rainbow trout (resulting in cutbows)[17] 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.[18]

Notes

  1. ^ Deeds, Scott A.; Kaeding, Lynn R.; Lohr, Samuel C.; Young, Douglas A.; Campton, Don; Duke, Steve; Mogen, Jim T. (September 1999). Status Review for Westslope Cutthroat Trout in the United States. U.S. Fish and Wildlife Service. p. 7. Retrieved 2014-02-20.
  2. ^ "Synonyms of Oncorhynchus clarkii (Richardson, 1836)". Fishbase. Retrieved 2014-02-19.
  3. ^ "Montana Field Guide-Westslope Cutthroat". Montana Department of Fish, Wildlife and Parks. Retrieved 2010-12-11.
  4. ^ 1-1-507. State fish Archived 2013-01-17 at the Wayback Machine, Montana Code, accessed 23 April 2009.
  5. ^ 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 species of concern reports for more detailed explanations and assessment criteria. "Montana Field Guide-Species of Concern". Retrieved 2010-12-07.
  6. ^ "Aquatic Species at Risk - The Westslope Cutthroat Trout (British Columbia Population)". Fisheries and Oceans Canada. Retrieved 2014-02-19.
  7. ^ "Aquatic Species at Risk - The Westslope Cutthroat Trout (Alberta Population)". Fisheries and Oceans Canada. Retrieved 2014-02-19.
  8. ^ a b Richardson, John; William Swainson; William Kirby (1836). Fauna boreali-americana, or, The zoology of the northern parts of British America: containing descriptions of the objects of natural history collected on the late northern land expedition, under command of Captain Sir John Franklin, R.N. London: J. Murray. pp. 225–226.
  9. ^ a b Behnke, Robert J.; Tomelleri, Joseph R. (illustrator) (2002). "Cutthroat trout Oncorhynchus clarki". Trout and Salmon of North America. The Free Press. pp. 137–234. ISBN 0-7432-2220-2.
  10. ^ a b c d Behnke, Robert J.; Tomelleri, Joseph R. (illustrator) (2002). "Westslope cutthroat trout Oncorhynchus clarkii lewisi". Trout and Salmon of North America. The Free Press. pp. 155–162. ISBN 0-7432-2220-2.
  11. ^ Jordan, David Starr; Evermann, Barton Warren (1896). A Check-list of the Fishes and Fishlike Vertebrates of North and Middle America. U.S. Commission of Fish and Fisheries. p. 291.
  12. ^ Jordan, David Starr; Evermann, Barton Warren (1898). The Fishes of North and Middle America Part III. Smithsonian Institution. p. 2819.
  13. ^ Smith, Gerald R.; Stearley, Ralph F. (1989). "The Classification and Scientific Names of Rainbow and Cutthroat Trouts" (PDF). Fisheries. American Fisheries Society. 14 (1): 4–10. doi:10.1577/1548-8446(1989)014<0004:TCASNO>2.0.CO;2. hdl:2027.42/140998.
  14. ^ Behnke, Robert J.; Tomelleri, Joseph R. (illustrator) (2002). "Genus Oncorhynchus". Trout and Salmon of North America. The Free Press. pp. 10–21. ISBN 0-7432-2220-2.
  15. ^ Kevin Goodson; Bruce McIntosh; Mark Chilcote; Charlie Corrarino, eds. (2005). "Oregon Native Fish Status Report" (PDF). Oregon Department of Fish and Wildlife. pp. 452–457. Retrieved 2014-02-20.
  16. ^ Young, Michael K., ed. (1995). Conservation Assessment for Inland Cutthroat Trout (General Technical Report (GTR) RM-GTR-256). Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. p. 61. doi:10.2737/RM-GTR-256. hdl:2027/umn.31951d029777160.
  17. ^ Hitt, N.P., et al. (2003) Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarkii lewisi, and nonnative rainbow trout, Oncorhynchus mykiss. Can. J. Fish. Aquat. Sci. 60, 1440-1451. doi:10.1139/F03-125
  18. ^ Muhlfeld, Clint C.; Kovach, Ryan P.; Jones, Leslie A.; Al-Chokhachy, Robert; Boyer, Matthew C.; Leary, Robb F.; Lowe, Winsor H.; Luikart, Gordon; Allendorf, Fred W. (July 2014). "Invasive hybridization in a threatened species is accelerated by climate change". Nature Climate Change. 4 (7): 620–624. Bibcode:2014NatCC...4..620M. doi:10.1038/nclimate2252. ISSN 1758-6798.

Further reading

External links

Cutthroat trout subspecies and forms
Trout and char of the world
Taxon identifiers
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