Cutthroat-Forelle

Systematik

Vorlage:About The cutthroat trout (Oncorhynchus clarki) is a species of salmonid native to cold-water tributaries of the Pacific Ocean, Rocky Mountains and Great Basin in North America. As a member of the genus Oncorhynchus it is one of the Pacific trouts which include the widely distributed rainbow trout. Cutthroat trout are popular gamefish, especially among anglers who enjoy fly fishing. The common name "cutthroat" refers to the distinctive red coloration on the underside of the lower jaw.

Several subspecies of cutthroat are currently listed as threatened in their native ranges due to habitat loss and introduction of non-native species. Two subspecies, O. clarki alvordensis and O. clarki macdonaldi are considered extinct. Cutthroat trout are raised in hatcheries to restore native populations as well as stock non-native lascustrine environments to support angling.

The cutthroat trout type species and several subspecies are the state fish in seven western U.S. states.

Taxonomy

The scientific name of the cutthroat trout is Oncorhynchus clarki. The species was first described in the journals of William Clark from specimens obtained during the Lewis and Clark Expedition from the Missouri river near Great Falls, Montana. These were most likely the westslope cutthroat trout (Oncorhynchus clarki lewisi). Cutthroat trout were given the name Salmo clarki in honor of William Clark, who co-led the expedition of 1804–1806. 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 from a tributary of the lower Columbia River, identified as the "Katpootl", 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.

In 1989, morphological and genetic studies by Dr. Gerald R. Smith, Curator of Fishes at the Museum of Zoology, University of Michigan and Ralph F. Stearley, doctoral candidate, Museum of Palentology, University of Michigan indicated that trouts of the Pacific basin were genetically closer to Pacific salmon (Onchorhynchus species) than to the Salmos–brown trout (Salmo trutta) or Atlantic salmon (Salmo salar) of the Atlantic basin. Thus, in 1989, taxonomic authorities moved the rainbow, cutthroat and other Pacific basin trouts into the genus Onchorhynchus.

Subspecies

There are many subspecies of cutthroat, each native to a separate geographic area. The cutthroat trout is thought by scientists to have evolved over the past two million years from other Oncorhynchus species which migrated up the Columbia and Snake river basins. There are at least 10, and perhaps more than 14 subspecies, including:

Pacific Coast

• Coastal cutthroat trout O. c. clarki, also known as "sea-run" cutthroat; native from northern California to Alaska.
  • Crescenti trout O. c. crescenti, no longer a recognized subspecies, but a unique population of coastal cutthroat endemic to Lake Crescent, Washington state.

Great Basin

Likely O. c. utah
Bonneville cutthroat trout

• Alvord cutthroat trout O. c. alvordensis, endemic to tributaries of Alvord Lake in southeastern Oregon; considered extinct. Named in 2002.
• Bonneville cutthroat trout O. c. utah, native to tributaries of the Great Salt Lake.
• Humboldt cutthroat trout O. c. spp., found only in the upper Humboldt River of northern Nevada. Considered by some to be a population of O. c. henshawi.
• Lahontan cutthroat trout O. c. henshawi, western Nevada, designated as threatened.
  • Whitehorse Basin cutthroat trout, O. c. spp., once considered a separate subspecies, native to southeastern Oregon.
• Paiute cutthroat trout O. c. seleniris, endemic to eastern Sierra Nevada Mountains, designated as threatened.

Northern Rockies

O. c. bouvieri
Yellowstone cutthroat trout

• Snake River fine-spotted cutthroat trout, named O. c. behnkei (1995 & 2002), but some consider it a population of O. c. bouvieri. Native to the Snake River of Idaho and Wyoming.
• Westslope cutthroat trout O. c. lewisi, native to northern Idaho, Montana, British Columbia, and Alberta.
• Yellowfin cutthroat trout O. c. macdonaldi, endemic to Twin Lakes, Colorado; now extinct.
• Yellowstone cutthroat trout O. c. bouvieri, native to the upper Snake River, Yellowstone Lake, and Yellowstone River, in Idaho, Montana and Wyoming.

Southern Rockies

O. c. virginalis
Rio Grande cutthroat trout

• Colorado River cutthroat trout O. c. pleuriticus, native to tributaries of the Green and Colorado Rivers.
• Greenback cutthroat trout O. c. stomias, native to the Arkansas and South Platte Rivers in eastern Colorado; designated as threatened.
• Rio Grande cutthroat trout O. c. virginalis, native to New Mexico and southern Colorado.

Description

Throughout their native and introduced range, cutthroat trout vary widely in size, coloration, and habitat selection. Though their coloration can range from golden to gray to green on the back, and depending on subspecies strain and habitat, they usually feature distinctive red, pink, or orange linear marks along the underside of the mandible in the lower folds of the gill plates; the easiest diagnostic of the species for the casual observer. These markings are responsible for the formation of the typical name "cutthroat". At maturity, different populations and subspecies of cutthroat can range from 6–40 inches (15–100 cm) in length, depending on habitat and food availability, making size an ineffective indicator as to species identity. Cutthroat trout are prized as a sportfish, particularly by fly anglers, as their propensity to inhabit remote waters and diminutive streams appeals to the sense of adventure present in many outdoor enthusiasts. In addition, their tendency to exhibit significant activity and resistance to anglers in conjunction with this species' affinity for terrestrial or mature insects serves to increase popularity of the cutthroat as an angler's quarry. Finally, the cutthroat participates in a unique predator-prey relationship with the bull trout that is key to ecosystem integrity across much of its natural range.

Life cycle

Cutthroat naturally interbreed with the closely related rainbow trout, producing fertile hybrids commonly called "cutbow". As this species generally bears similar coloration and overall appearance to the cutthroat, retaining the characteristic orange-red slash, these hybrids often pose a taxonomical difficulty. In addition, cutthroat will also hybridize with the O. gilae subspecies, the Gila trout and Apache trout in regions where their ranges overlap.

Range and habitat

Stocking cutthroat trout at Pyramid Lake, Nevada, in 1973

Cutthroat trout are native to western North America. The cutthroat species has evolved through geographic isolation into many subspecies, each native to a different major drainage basin. Native cutthroat species are found along the Pacific Northwest coast from Alaska through British Columbia into northern California, in the Cascade Range, the Great Basin, and throughout the Rocky Mountains including southern Alberta. Some coastal populations of the coastal cutthroat trout (O. clarki clarki) are semi-anadromous, spending a few months in marine environments to feed as adults and returning to fresh water from fall through early spring to feed on insects and spawn. Cutthroat trout have the second largest native range of North American trouts, the lake trout having the largest.

Most populations stay in freshwater throughout their lives and are known as non-migratory, stream-resident or riverine populations. Anadromous fish may reach weights of Vorlage:Convert, but those fish which remain permanently in freshwater may only reach a weight of Vorlage:Convert. The coastal cutthroat trout (O. clarki clarki) is the only cutthroat subspecies to co-evolve through its entire range with the coastal rainbow trout (O. mykiss irideus). Portions of the westslope cutthroat trout's (O. clarki lewisi) overlap with the Columbia river redband trout (O. mykiss gairdneri), but the majority of its native range is in head water tributary streams above major waterfalls and other barriers to upstream migration. At least three subspecies are confined to isolated basins in the Great Basin and can tolerate saline or alkaline water.

Artificial propagation

Various subspecies of cutthroat trout are raised in commercial, state and federal hatcheries for introduction into suitable native and non-native riverine and lacustrine environments. In the early 20th century, a number of hatcheries were established in Yellowstone National Park by the U.S. Bureau of Fisheries. These hatcheries not only produced stocks of the Yellowstone cutthroat trout O. clarki bouvieri for the park, but also took advantage of the great spawning stock of cutthroat trout to supply eggs to hatcheries around the U.S. Between 1901 and 1953, 818 million trout eggs were exported from the park to hatcheries throughout the U.S. The Lahontan National Fish Hatchery operated by the U.S. Fish and Wildlife Service exists to restore populations of the Lahontan cutthroat trout O. clarki lahontan in Pyramid, Walker, Fallen Leaf, June, Marlette, Gull lakes and the Truckee River in California and Nevada. The hatchery produces approximately 300,000–400,000 Lahonton cutthroat trout annually. The Jackson National Fish Hatchery approximately 400,000 Snake river fine-spotted cutthroat trout O. clarki behnkei annually to support fisheries in Idaho and Wyoming.

Population threats

The overall native range of cutthroat trout has been reduced by overfishing, urbanization, and habitat loss due to mining, grazing, and logging. Population densities have been reduced and in some cases populations have disappeared though competition with non-native brook, brown and rainbow trout which were introduced in the late 19th and early 20th centuries. However the most serious current threats to several subspecies interspecific breeding with introduced rainbow trout creating hybrid cutbows and intraspecific breeding with other introduced cutthroat sub-species. In the Greater Yellowstone Ecosystem, the presence of lake trout in Yellowstone Lake in Yellowstone National Park has caused serious decline in O. clarki bouvieri. Outbreaks of whirling disease in major spawning tributaries have also caused declines.

From Birds and nature, 1904

Although lake trout were established in Shoshone, Lewis and Heart 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 accidental or illegal introductions. Cutthroat trout co-exist with lake trout in Heart lake, an isolated back-country lake at the head of the Heart river that gets little angling pressure.

Whirling disease

Most sub-species of cutthroat trout are highly susceptible to whirling disease, Myxobolus cerebralis. The Snake river fine-spotted cutthroat trout sub-species O. clarki behnkei appears to be resistant to the parasite.

Symbol

The cutthroat trout is the state fish of Idaho and Wyoming, while particular subspecies of cutthroat are the state fish of Colorado, Montana, Nevada, New Mexico, and Utah.

Origin of the name

The common name "cutthroat" refers to the distinctive red coloration on the underside of the lower jaw.

Notes

Wikispecies: Oncorhynchus clarki – Artenverzeichnis

Further reading

• Terry Barron: Guide to Fly Fishing Pyramid Lake A Quick Clear Understanding of the Nations Top Lahontan Cutthroat Trout Fishery. No Nonsense Fly Fishing Guidebooks, Tucson, AZ, ISBN 978-0-9637256-3-9. 
• Les Johnson: Sea-run Cutthroat Trout. Frank Amato Publishers, Portland, OR 1976, ISBN 978-0-936608-02-0. 
• Les Johnson: Fly-Fishing Coastal Cutthroat Trout: Flies, Techniques, Conservation. Frank Amato Publishers, Portland, OR 2004, ISBN 978-1-57188-334-6. 
• Jim Rubingh: Colorado Greenback Cutthroat Trout: A Fisherman's Guide. Frank Amato Publishers, Portland, OR 2009, ISBN 978-1-57188-447-3. 
• Patrick C. Trotter: Cutthroat: Native Trout of the West. 2nd Auflage. University of California Press, Berkley, CA 2008, ISBN 978-0-520-25458-9.