Lahontan cutthroat trout

Lahontan cutthroat trout
O. clarki henshawi, Pyramid Lake, Nevada
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Salmoniformes
Family:	Salmonidae
Genus:	Oncorhynchus
Species:	O. clarki
Subspecies:	O. c. henshawi
Trinomial name
Oncorhynchus clarki henshawi (Richardson, 1836)

Main article: Cutthroat trout

Lahontan cutthroat trout (Oncorhynchus clarki henshawi) is the largest subspecies of cutthroat trout, and the state fish of Nevada.

Natural history

The Lahontan cutthroat is native to the drainages of the Truckee River, Humboldt River, Carson River, Walker River, Quinn River and several smaller rivers in the Great Basin of North America. These were tributaries of ancient Lake Lahontan during the ice ages until the lake shrank to remnants such as Pyramid Lake and Walker Lake about 700 years ago, although Lake Tahoe -- from which the Truckee flows to Pyramid Lake -- is still a large mountain lake.

Lahontan cutthroats evolved into a large (up to 1 metre (39 in)) and moderately long-lived predator of chub, suckers, and other fish as long as 30 or 40 centimetres (16 in). The trout was able to remain a predator in the larger remnant lakes where prey fish continued to flourish, but upstream populations were forced to adapt to eating smaller fish and insects. Some experts consider O. c. henshawi in the upper Humboldt River and tributaries to be a separate subspecies (the "Humboldt cutthroat trout"), adapted to living in small streams rather than large lakes.

The record size cutthroat trout of any subspecies was a Lahontan caught in Pyramid Lake weighing 41 pounds (18.6 kg), although there is anecdotal and photographic evidence of even larger fish from this lake.

Human history

The Lahontan cutthroats of Pyramid and Walker Lakes were of considerable importance to the Paiute tribe. These trout as well as Cui-ui -- a sucker found only in Pyramid Lake -- were dietary mainstays and were used by other tribes in the area. During the 19th century and early 20th centuries, Lahontan cutthroats were caught in tremendous numbers and shipped to towns and mining camps throughout the West; estimates have ranged as high as 1,000,000 pounds (450,000 kg) annually between 1860 and 1920.

American settlement in the Great Basin nearly extirpated these remarkable fish. A dam in Mason Valley blocked spawning runs from Walker Lake. By 1905 Derby Dam on the Truckee River below Reno interfered with Pyramid Lake's spawning runs. A poorly designed fish ladder washed away in 1907, then badly-timed water diversions to farms in the Fallon, Nevada area stranded spawning fish and desiccated eggs below the dam. By 1943 Pyramid Lake's population was extinct. Lake Tahoe's population was extinct by 1930 from competition and inbreeding with introduced rainbow trout (creating cutbows), predation by introduced Lake trout, and diseases introduced along with these exotic species.

Upstream populations have been isolated and decimated by poorly-managed grazing and excessive water withdrawals for Irrigation, as well as by hybridization and competition.

Pyramid Lake and Truckee River water quality

Pyramid Lake, the second largest natural lake in the western U.S. prior to construction of the Derby Dam, has been the focus of several water quality investigations, the most detailed starting in the mid-1980s. Under direction of the U.S. Environmental Protection Agency, a comprehensive dynamic hydrology transport model was developed (C.Michael Hogan et al. 1987) by Earth Metrics Inc.; the model's name was subsequently changed to DSSAM, and it was applied to analyze impacts of a variety of land use and wastewater management decisions throughout the 3,120-square-mile (8,100 km²) Truckee River Basin. These analyses allowed more competent decisions to be made regarding non-point runoff in the watersheds as well as management of treated effluent discharged to the Truckee River.

Conservation

Pyramid and Walker Lakes have been re-stocked with fish captured in Summit Lake (Nevada) and Lake Heenan, and those populations are maintained by fish hatcheries. Unfortunately the Summit Lake strain does not live as long or grow as large as the original strain of fish. However fish believed to have been stocked almost a century ago from the Pyramid Lake strain were discovered in a small stream along the Nevada-Utah border, and may eventually be used to restore the original strain.

They were classified as an endangered species between 1970 and 1975, then the classification was relaxed to threatened species.

Because it tolerates water too alkaline for other trout, Lahontan cutthroats are stocked in alkaline lakes outside its native range, including Lake Lenore (alternately Lenore Lake) in central Washington and Lake Mann in Oregon's Alvord Desert east of Steens Mountain.

See also

1938 remarks by FDR on the taste of Nevada trout

DSSAM Model

References

• William F. Sigler and John W. Sigler, Fishes of the Great Basin (Reno: University of Nevada Press, 1987), pp. 110–118

• C.Michael Hogan, Marc Papineau et al., Development of a dynamic water quality simulation model for the Truckee River, Earth Metrics Inc., Environmental Protection Agency Technology Series Washington D.C. (1987)
• Robert J. Behnke, "Native Trout of Western North America" (Bethesda: American Fisheries Society Press, 1992)

External links