Oncorhynchus clarki henshawi
A lahontan cutthroat from the headwaters of a stream in Sierras of California.
Lahontan cutthroat are one of the four major subspecies of cutthroat trout and are native to the Lahontan Basin of Nevada, California, and a small part of Oregon. These trout evolved to a lacustrine environment in ancient Lake Lahontan, which existed during the last ice age and was about the size of present day Lake Erie. As the level of Lake Lahontan dropped, the lake's cutthroat became isolated throughout the basin. This is reflected by their current distribution in a handful of lakes and streams in the higher elevation fringes of the basin. Lahontan cutthroat have also been stocked in a number of arid lakes with high alkalinity throughout the Western United States.
Historically Lahontan cutthroat occurred as lacustrine, fluvial and stream resident populations. However it is with the lacustrine life history that these fish reached their true potential and the best representation of this was the population found in Pyramid Lake in Nevada. Even though Pyramid Lake is highly alkaline with a pH of 9.4, Lahontan cutthroat thrive there and it once produced the largest cutthroat on the planet. The largest recorded cutthroat from Pyramid Lake was 41 pounds, although members of the Paiute Indian tribe claim to have caught fish in excess of 60 pounds (Behnke 2002). A distinctive trait that Lahontans possess is this tolerance for high levels of alkalinity in the water that they live in. This trait most likely arose from being exposed to slowly increasing salinity and alkalinity levels, which over a number of generations allowed them to process excess amounts of dissolved solids that would be lethal to other trout (Wright et al. 1993).
These fish also occurred in a number of other lakes throughout the Lahontan basin, including Lake Winnemucca, Lake Tahoe, Summit and Walker Lakes. Lahontan cutthroat are opportunistic feeders and while in the lacustrine environment they will become piscivorous when large enough as long as baitfish are available (Behnke 1992). In Pyramid Lake mature fish feed primarily on the tui chub, while juveniles feed on zooplankton, aquatic insects and other invertebrates (Sigler et al. 1983). Fish from Pyramid Lake were known to have distinct fall, winter and spring spawning runs although all of these fish actually spawned during the spring (Trotter 2008). All known population of lacustrine Lahontan cutthroat utilized riverine environments as spawning habitat and not the lakes themselves. Pyramid Lake fish generally spawn for the first time at between two to four years old, with the bulk of the females being three to four years old and the males two to three years old (Sigler et al. 1983). Cutthroat from Lake Tahoe and Pyramid Lake were known to spawn in all of the suitable habitat in the Truckee River and fish from Walker Lake ran as far as 125 miles up the Walker River to reach their spawning grounds (Trotter 2008). Today the only lacustrine population for Lahontan cutthroat that has not be exasperated due to habitat degradation or impacted by non-native fish occurs in Summit Lake in Nevada. Adult spawners in this population are known to return to Summit Lake between the end of April and the end of July, while young of year juvenile fish migrate to the lake for the first time between August and the end of October (Vinyard and Winzeler 2000).
Stream resident Lahontan cutthroat are still found in isolated headwater reaches of many streams along the periphery of the basin. As with many trout found in arid portions of the western United States these trout have adapted to survive under extreme conditions. The upper temperature limit for Lahontan cutthroat appears to be between 71 and 75 degrees Fahrenheit, with 60% of fish dying when exposed to a temperature of 79 degrees Fahrenheit for one week (Dickerson and Vinyard 1999). Typically speaking stream resident fish do not travel very far from their home territory and Stead (2007) showed that daily movements of a reestablished stream resident population were less than three hundred feet. Stream resident populations may spawn anywhere from April to July depending on altitude and climate and it takes the eggs four to six weeks to hatch (Trotter 2008).
The Lahontan cutthroat have suffered major declines across their entire native range and as a result they were one of the first fish listed Endangered Species Act (ESA) in 1973 and are still listed as threatened today. These declines stemmed from a variety of issues including dams, habitat degradation and competition and hybridization with non-native fish. As a result of wild populations of Lahontan cutthroat were written off as extinct by the 1960's. Since then prospects for the Lahontan cutthroat have improved some and thanks to restoration efforts they are beginning to regain of the habitat that they once were found in. Even so self sustaining populations of lacustrine and stream resident fish are fairly rare and as far as I am aware of the fluvial life history component no longer occurs.
Perhaps one of the greatest populations to be lost was the Pyramid Lake population, which historically produced the world's largest cutthroat. This population was lost shortly after the completion of Derby dam, which was is located 30 miles up the Truckee River from Pyramid Lake. The dam was built for irrigation purposes and did not include a fish ladder to allow the fish to migrate to the upper river. Over time more and more water was diverted from the Truckee River and by the 1930's to little water was making it to the lower river to allow for successful spawning. The last spawning run occurred in 1938 and observers noted that the fish averaged 36" long and 20 pounds in weight (Behnke 2002). The Lahontan cutthroat native to Walker Lake shared a similar fate after a dam was erected on the Walker River. However in this case the diversion of the Walker River also caused the lake level to drop by over 100 feet, making the lake even more alkaline and leading to very poor rates of survival for the cutthroat (Trotter 2008). This population is currently maintained through a hatchery egg taking program.
Since there exasperation from Pyramid Lake, Lahontan cutthroat of Summit and Heenan Lake origin have been reintroduced into the lake. However they do not attain the weights that the original stock once did and as with the Walker Lake fish their continued existence is completely dependent on hatchery supplementation. While for years it was thought that the original Pyramid Lake cutthroat lineage was gone forever, in 1977 a population of Lahontan cutthroat trout of Pyramid Lake origin were discovered in a stream draining Pilot Peak on the Utah-Nevada border (Hickman and Behnke 1979). It is hoped that the lacustrine life history type that once produced such large fish in Pyramid Lake may be revived from this population some day.
Due to its long isolation in the Lahontan Basin, the Lahontan cutthroat is highly differentiated from other the other subspecies of cutthroat. The coloration of the Lahontan cutthroat is generally rather drab, with a greenish bronze color along the back transitioning to a light brassy-yellow color along the sides (Behnke 2002). The coloration of lacustrine fish is often rather silvery and as males approach spawning they typically develop an intense red color along their sides. A rose to coppery red color is often present along the lateral line and on the gill plates as well. The coloration of the lower fins is typically a reddish-purple color with white edges. Large round spots are distributed across the entire body and along the top of the head. Like other cutthroat, these fish exhibit a pale red or orange cutthroat mark below the lower jaw.
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