Restoration of Bonneville cutthroat trout populations in Great Basin
By Neal W. Darby
neal_darby@nps.gov
Fish and Wildlife Biologist, Great Basin National Park, Nevada
Since ancient Lake Bonneville dried up 8,000 years ago in what is now eastern Nevada and Utah, Bonneville cutthroat trout (Oncorhynchus clarki utah) have persisted in the isolated small mountain streams of the eastern Great Basin. Unfortunately, water diversions, subsistence harvest, and especially stocking with nonnative fish caused the extirpation of the Bonneville cutthroat trout from most of its range. The local extinction was so widespread that the U.S. Fish and Wildlife Service is now conducting a second status review for listing the trout under the Endangered Species Act of 1973. However, Great Basin National Park near Baker, Nevada, on the Nevada-Utah border provided a unique opportunity to promote conservation of the trout and potentially preclude the need for listing it in eastern Nevada.
The Bonneville cutthroat trout was believed to be extinct in Great Basin National Park because past surveys revealed only nonnative hatchery fish or hybrids of the Bonneville cutthroat and rainbow trout (O. mykiss). After the park established a reintroduction program for the trout in 1998, a survey in one stream system of the park in 2000 revealed only fish with strong characteristics of the Bonneville cutthroat trout. Subsequent genetic analysis of fin tissues confirmed the presence of a pure population of the species. The timely discovery of the trout was fortunate because cleansing of the stream system with chemicals to remove the nonnative trout and the hybrids that were thought to be there was planned as the next step in the reintroduction program. Instead of being inadvertently annihilated, the population is now being genetically compared with other populations of the Bonneville cutthroat trout in nearby streams. If appropriate, the preservation of the genetic stock that developed in the park will be attempted.
With discovery of this population, a source stock became available for reintroductions elsewhere in the park. The park established a new population of Bonneville cutthroat trout in a stream of another watershed by transplanting 60 trout from the source stock. Another historical Bonneville cutthroat trout stream has been chemically cleansed to remove the nonnative fish and hybrids in preparation for a reintroduction of Bonneville cutthroat trout in 2001. Private landowners adjacent to the park supported a more diversified fishery and allowed chemical cleansing of streams on their lands. The extension of cleansing beyond park boundaries may facilitate restoration of a native fishery throughout an entire watershed.
The intensive surveys to determine the need for chemical cleansing of streams in the park revealed not only the Bonneville cutthroat trout but also another group of sensitive species, the Great Basin spring snails (Pyrgulopsis spp.). To protect these sensitive organisms from adverse effects of chemicals, the park adjusts the timing and extent of chemical cleansing. Such proactive work prevents the need for listing the species under the Endangered Species Act. It also benefits neighboring federal land agencies, the state, private landowners, and the public by allowing continued multiple land use with fewer restrictions.
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Conservation of the Bonneville cutthroat trout in Great Basin National Park may preclude the need for listing the species as threatened under the Endangered Species Act.
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A stream survey in Great Basin National Park, followed by genetic analysis in 2000, confirmed a pure population of rare Bonneville cutthroat trout. The local population subsequently became a source for restoration of the species in a different park watershed.
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Last Updated: 06/17/2001
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