Preparer

Gary L. Vinyard, Department of Biology, University of Nevada, Reno, Nevada, USA. 89557-0015

Conservation Status

Threatened (U.S. Fish and Wildlife Service, 1975, Federal Register 40:29864)

Identification

Coloration is variable but generally heavily marked with large rounded black spots, more or less evenly distributed over the sides, head and abdomen. Gill rakers 21-28, average 23-26, pyloric cecae 40-70, generally more than 50, basibranchial teeth present (Behnke 1992, LaRivers 1962).

Distribution

The only trout native to the Lahontan subbasin of the American Great Basin, west-central Nevada, USA. Historically found in the Carson, Humboldt, Truckee, and Walker Rivers, and their tributary lakes and streams. This range reflects the likely dispersal through Pleistocene lakes which occupied many of the interior valleys of the region.

Abundance

At the beginning of the 19th century, Lahontan cutthroat trout were apparently abundant and widespread. It is estimated that >6100 km of stream habitat and 120,300 Ha of lake habitat were occupied by the fish at that time. Since the late in the last century, loss of habitat, overfishing, and introductions of non-native fishes have reduced fluvial and lacustrine populations to approximately 10.7% and 0.4%, of their original habitat, respectively (Coffin 1981, Coffin and Cowan 1995).

Habitat and Ecology

Lahontan cutthroat occupy a great variety of habitats. Populations were historically abundant in large rivers (eg. Carson, Humboldt, Truckee, and Walker Rivers) and lakes (eg. Pyramid, Walker, Summit, Independence Lakes). They also inhabit small tributary streams. These fish are unusually tolerant of both high temperatures (>27°C) and large daily fluctuations (up to 20°C). They are also quite tolerant of high alkalinity (>3000 mg/l) and dissolved solids (>10000 mg/l). They are apparently intolerant of competition or predation by non-native salmonids, and rarely coexist with them (Behnke 1992, LaRivers 1962, Trotter 1987).

Reproduction

Lahontan cutthroat are obligate but opportunistic stream spawners. Typically, they spawn from April through July (though sometimes later), depending on water temperature and flow characteristics. Autumn spawning runs have been reported from some populations. The fish may be iteroparous, though post spawning mortality rates of 60 - 90 % have been reported. Lake residents migrate into streams to spawn, typically on well washed gravels in riffles. Behavior is typical of stream spawning trout. Adults court, pair, deposit and fertilize eggs in a redd dug by the female. The redd may then be defended for some period. Spawning fish in particular develop bright red coloration on the underside of the mandible and on the opercle. Coloration is more intense in males which also show change in shape of the lower jaw during spawning.

Threats

Habitat loss and the adverse impacts of non-native fishes continue to be the primary threats to these fish (Coffin and Cowan 1995, Gerstung 1988).

Conservation Action

A Species Recovery Plan has been prepared by the U.S. Fish and Wildlife Service (Coffin and Cowan 1995). This will includes recommendations for the preservation of existing populations and the establishment of additional populations in secure areas.

Conservation Recommendations

Protection of existing populations requires increased monitoring and assessment of population levels and exclusion of non-native fishes. Reintroduction into areas capable of supporting Lahontan cutthroat trout will improve prospects for survival.

Remarks

Conservation of this fish is important for both conservation and recreational reasons. It was an important commercial resource in Lake Tahoe and Pyramid Lake for several decades at the beginning of this century and still is a significant gamefish. The now extinct stock of cutthroat trout from Pyramid Lake apparently produced the largest individuals recorded for this species, greater than 18 kg. Lahontan cutthroat trout were a primary food source for several of the indigenous Indian tribes living within the Great Basin, and were an important cultural resource.

References

Coffin, P. 1981. Distribution and life history of the Lahontan/Humboldt cutthroat trout- Humboldt River drainage Basin. Nevada Department of Wildlife. Reno.

Coffin, P. and W. Cowan. 1995. Lahontan cutthroat trout (Oncorhynchus clarki henshawi) recovery plan. U.S. Fish and Wildlife Service, Region 1. Portland, Oregon.

Behnke, R.J. 1992. Native trout of Western North America. Am. Fish. Soc. Monog. 6.

Gerstung, E. 1988. Status, life history and management of the Lahontan cutthroat trout. Am. Fish. Soc. Symp. 4:93-106.

LaRivers, I. 1962. Fish and Fisheries of Nevada. Nevada State Fish and Game Commission. Carson City.

Trotter, P.C. 1987. Cutthroat, Native trout of the West. Colorado Associated Univ. Press. Boulder.

This file is originally from the Biological Resources Research Center at the University of Nevada, Reno. For more information email gvinyard_at_unr.edu

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