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<br />374 <br /> <br />CHAPTER 15 <br /> <br /> <br />Figure 15.4 Low log dams in streams are often used to enhance pool habitat for western <br />trouts. (Photograph courtesy of K. Fausch.) <br /> <br />habitats, rather than all areas occupied by a species, need to be identified and <br />designated for preservation. Recovery planning on an ecosystem basis has proven <br />more effective than the conventional species-by-species approach. <br />Restoration of damaged or depleted habitat is also possible. Earlier, we <br />discussed attempts to restore the habitat of the Devils Hole pupfish by shelf <br />construction. Re-creating backwaters, wetlands, embayments, and other habitat <br />types has been suggested to aid recovery of the protected native fishes of the <br />Upper Colorado River system. Use of fishways and other remediation measures <br />has also been suggested to preserve those species. Rinne (1982) described effects <br />of log habitat-improvement structures on Gila trout growth and dispersal; similar <br />techniques have been applied to streams containing other rare western trouts <br />(Figure 15.4). Restoration of aquatic habitat might also include removal of dams, <br />returning channelized streams to their original courses, silt removal, and restora- <br />tion of riparian vegetation. <br />Our case histories included examples of transferring threatened fishes to <br />refugia. One of the earliest transfers was that of the Owens pupfish. Thought to be <br />extinct when it was described in 1948, it was later rediscovered in Fish Slough in <br />Mono County, California (Miller and Pister 1971). To protect the remnants of the <br />species from introduced predatory fishes and competition from mosquitofish, the <br />Owens Valley Native Fish Sanctuary was built by the California Department of <br />Fish and Game in 1969. Owens River fishes were moved to the sanctuary in 1970. <br />Two other refugia were later constructed to receive the Owens pupfish and other <br />native Owens Valley fishes, and all have contributed to their continued existence. <br />Fish in such refugia generally are not representative of endemic native species <br />(Ono et aI. 1983). New selection pressures are expected to adapt them to their <br />refugia and alter their gene pools. Turner (1984), however, found no apparent loss <br />