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Photo Courtesy of Utah Division of Wildlife Resources
Lahontan Cutthroat Trout
Oncorhynchus clarkii henshawi
NatureServe conservation status
Global (G-rank): G4T3
State (S-rank): SNA
- Reason: This subspecies has been established in two streams in the Pilot Peak Range, Box Elder County, near the Nevada border. Because of extirpation and interbreeding elsewhere, the Utah population may represent the only surviving genetically pure population.
External links
General information
The Lahontan cutthroat trout, Oncorhynchus clarkii henshawi, is a race of the cutthroat trout native to the Lahontan Basin of Oregon, California, and western Nevada. It has been introduced and become established in the Pilot Peak Range of western Box Elder County, Utah. The Lahontan cutthroat trout is a Federally listed threatened species.
The Lahontan cutthroat trout is the largest of all cutthroat races. Like other cutthroat races, the Lahontan cutthroat is an opportunistic feeder, with the diet of small individuals dominated by invertebrates, and the diet larger individuals composed primarily of fish.
The Lahontan cutthroat trout is adapted to live in saline and alkaline lakes and streams. It is now very rare, currently occurring in only a small percentage of its native range. Major threats to the Lahontan cutthroat trout include the loss and alteration of spawning habitat, competition with nonnative fishes, and hybridization with nonnative trout.
Species range
This species is found in the Pilot Peak Range, Box Elder County, in two small creeks: Morrison Creek (called "Donner Creek" by Hickman and Duff [1978] and Hickman and Behnke [n.d.]) and Bettridge Creek.
Migration
Migration distance varies with population; reportedly, migrations of over 100 miles formerly occurred in the Truckee River (see USFWS 1994).
Habitat
Occupied habitat in the Pilot Range has not been well-documented. The streams are quite small and narrow, and most areas are overgrown with dense vegetation (fide P. Thompson, UDWR). Hickman and Behnke (n.d.) noted that Morrison Creek is perennial, but diverted below 5,900 ft. Within its native range, the subspecies occurred in lakes.
Food habits
Opportunistic feeder (Behnke 1992). Small individuals eat small invertebrates such as crustceans and aquatic insects; larger fishes eat large invertebrates and samll fishes; fishes dominate the diet of large, lake-dwelling adults.
Reproductive characteristics
Life history characteristics are greatly influenced by the environment. Spawns in spring or early summer, the timing depending on stream flow and temperature. Spawning migrations have been observed at water temperatures of 5-16 C. Eggs hatch in 4-6 weeks (Spahr et al. 1991), and fry emerge 13 to 23 days later. Sexually mature in 2-3 years in streams, 3-5 years in lakes; males generally mature a year sooner than do females. Consecutive-year spawning by individuals is uncommon. Up to a few percent spawn a second time after an interval of one or more years (usually after at least two years). Longevity generally is less than 5 years in stream populations, up to 5-9 years in lakes (USFWS 1994).
Threats or limiting factors
Because populations are confined to just 2 small, hydrologically isolated streams, stochastic and catastrophic events are of highest concern. Also, illegal stocking of rainbow trout or other subspecies of cutthroat would jeopardize genetic integrity.
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
