Oncorhynchus clarki seleniris
A Paiute cutthroat from a small stream in California.
The Paiute cutthroat is a minor subspecies of Lahontan cutthroat that is distinguished from other cutthroat subspecies by an absence of spots along its body. Historically the Paiute cutthroat were only native to a single tributary of the Carson River, in California known as Silver King Creek, but today are also found in several formerly fishless streams. It is thought that these fish were isolated in Silver King Creek during a period of high water in ancient Lake Lahontan, which likely occurred during the last ice age. These trout have only narrowly escaped extinction in recent times and are currently closed to fishing in all of their native waters.
The Paiute cutthroat are only native to one small stream and as such they only exhibited a stream resident life history. However Paiute cutthroat have been shown to be able to successfully adapt to a lake environment as was shown by the successful stocking of Paiutes in Birchim Lake, CA in 1957. Unfortunately this population was later lost to hybridization with rainbow trout which were also stocked in the drainage.
Like other cutthroat subspecies, the Paiute cutthroat are a "spring" spawning fish and in their native watershed most spawning occurs between June and July due to the high elevation. Paiute cutthroat typically reach sexual maturity around age two or three and although they are iteroparous they rarely survive their first spawning event. Wong (1991) showed that only 3.8 percent of Paiute cutthroat in one of the transplanted Paiute populations survived past age three, with a few fish surviving to age five or six. The average female lays between 50 and 300 eggs and the fry generally emerging from the gravel after around 8 to 10 weeks depending on stream temperatures (Trotter 2008). Once they get large enough these trout will establish and defend territories and do not typically stray very far from their home range a problem that has complicated the establishment of refuge populations (Diana and Lane 1978). Like other stream resident trout Paiutes are opportunistic feeders and have a diet consisting primarily of aquatic and terrestrial insects. Paiute cutthroat generally reach a size of between 8 to 10 inches, but under ideal conditions (lake) may reach a size of up to 18 inches.
The Paiute cutthroat has one of the smallest native ranges of any North American trout and has very nearly gone extinct several times. In 1973 the Paiute cutthroat was listed as endangered under newly enacted Endangered Species Act (ESA), but by 1975 they were downlisted to facilitate restoration efforts (USFWS 2004). The single largest issue effecting the Paiute cutthroat has been the introduction of nonnative salmonids within their native range. Since the Paiute cutthroat historically did not have any interactions with other salmonids prior to the stocking of nonnatives into Silver King Creek they are very susceptible to both competition and hybridization. In fact Paiute cutthroat are currently extinct in their actual native range due to this issue and if it weren't for a young Shepard carrying a coffee can full of these fish over Llewellyn Falls (a barrier to fish migration) they wouldn't exist today (Benke 1992). For a time the these fish remained secure above the falls, but several stockings above the falls with both Lahontan cutthroat and rainbow trout nearly wiped them out again. Since then an effort to restore these trout has been underway, which has included eradicating the rainbows, lahontans and hybrids above the falls and creating several "safety net" populations in formerly fishless streams across California. Recent genetic testing has confirmed that the eradication efforts above Llewellyn Falls were successful as no hybrids were detected (Cordes et al. 2004).
While hybridization has been the biggest issue with the decline of the Paiute cutthroat there definitely have been other issues leading to their decline. Historically overfishing has been a problem and even though Silver King Creek above the falls is closed to all fishing, poaching has been an issue. Even more pressing than fishing pressure though, are concerns about habitat degradation. The Silver King Creek basin has been used extensively for grazing for the past 100 years and this has had an affect on the quality of the riparian habitat. One way that cattle grazing impacts these fish is by adding excessive loads of fine sediments into the streams (Kondolf 1994). This is especially detrimental to the survival of eggs as fine sediments smother them and cause the embryos to suffocate. Another issue in the Silver King Creek basin has been the presence of beavers which are not native but were introduced for trapping purposes. The dams that these animals create and the ponds behind them block spawning movements, silt in redds and can cause up to a 10-fold reduction in Paiute cutthroat numbers (Trotter 2008).
Being that the Paiute cutthroat are still extinct in their native stretch of Silver King Creek, they still are not out of the woods yet. The California Department of Fish and Game (CDFG) has been planning on restoring the Paiutes to this stretch of Silver King Creek below the falls for over a decade, but there have been some major bumps in the road. The first bump came in 2002 when the scheduled restoration was canceled due to a complaint with the U.S. District Court against the use of rotenone to eliminate the nonnative trout in drainage. Rotenone has been used in fisheries management for over 100 years and works by interfering with fish respiration (CDFG 2009). This chemical has long been used by native tribes as a way to catch fish, which are safe to eat since this rotenone is not easily absorbed by humans. In the doses that would been used for this type of project rotenone has not been shown to have any detrimental effects on humans or other mammals. Furthermore rotenone breaks down very quickly in the environment making it a great choice for this type of project. The CDFG tried again in 2005 and had everything in place at the stream to begin with the project with a last minute injunction was filed and the project was cancelled. Since then CDFG, US Fish and Wildlife Service and US Forest Service have been working together on an Environmental Impact Statement for the project with a decision to come down for the project in the near future. With any luck this project will get the green light and the Paiute cutthroat will become the first native trout to be restored to their entire native range.
The Paiute cutthroat is nearly identical to the Lahontan cutthroat in every way except for their spotting pattern. This factor distinguishes the Paiute from all other North American trout, as they are the only trout lacking any body spots. These trout may have some spots on their dorsal, adipose and caudal fins and while they lack body spots, parr marks are often retained into adulthood. The coloration of the Paiute cutthroat tends to be a brownish-olive on the back and transitions to a yellowish color along their sides and white along the belly. These trout typically exhibit a reddish colored band along their lateral line and the same color on their gill plates.
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