Ash Meadows National Wildlife Refuge (AMNWR) was established by the U.S. Fish and Wildlife Service (with the assistance of The Nature Conservancy) in 1984 to protect one of the highest concentrations of endemic flora and fauna in North America (Pister, 1985; Sada, 1990). Prior to federal acquisition, Ash Meadows had been anthropogenically altered, and non-native species had been introduced to the detriment of native species; reports and published literature document the negative effects to the Ash Meadows flora and fauna (Deacon and others, 1964; U.S. Department of the Interior, 1971; Landye, 1973; Pister, 1974; Soltz and Naiman, 1978; Taylor, 1980; Williams and others, 1985; Williams and Sada, 1985; Baugh and others, 1986; Hershler and Sada, 1987; Knight and Clemmer, 1987; Sada, 1990; Deacon and Williams, 1991; Scoppettone and others, 2005; Kennedy and others, 2006). Such activities led to the extinction of the endemic Ash Meadows poolfish (Empetrichthyes merriami) (Miller, 1961; Soltz and Naiman, 1978), and subsequently the federal government listed three local endemic fish as endangered pursuant to the Endangered Species Act (U.S. Fish and Wildlife Service, 1989)—Warm springs pupfish (Cyprinodon nevadensis pectoralis), Ash Meadows Amargosa pupfish (Cyprinodon nevadensis mionectes), and Ash Meadows speckled dace (Rhinichthys osculus nevadensis).

Public ownership of a large portion of Ash Meadows provided the opportunity to restore the landscape to some semblance of its historical condition. Elimination of invasive aquatic species may be more difficult than landscape restoration, and their persistence can cause additional native fish decline or extirpation (Taylor and others, 1984; Moyle and others, 1986; Miller and others, 1989; Minckley and Deacon, 1991; Olden and Poff, 2005). Chemical treatment to remove invasive fishes is often unsuccessful (Meffe, 1983; Rinne and Turner, 1991; Meronek and others, 1996). In Ash Meadows, there has been some success in chemical eradication of localized populations of largemouth bass (Micropterus salmoides) and black bullhead (Ameiurus melas) (St. George, 1998, 1999; Weissenfluh, 2008b), as well as convict cichlid (Archocentrus nigrofasciatus) and sailfin molly (Poecilia latipinna) (Weissenfluh,2008a). However, there has been less success in removing western mosquitofish (Gambusia affinis) from Ash Meadows’s larger spring systems, and sailfin molly maintains strongholds in several spring systems (Scoppettone and others, 2011b). Perhaps the more destructive invasive species are two invertebrates: red swamp crayfish (Procambarus clarkii) and red-rim melania (Melanoides tuberculata). Following the appearance of red swamp crayfish within the Warm Springs Complex, Warm Springs pupfish was believed to be extirpated from one spring system (St. George, 2000) and near extirpation in two others (Darrick Weissenfluh, Ash Meadows National Wildlife Refuge, oral commun., 2008, 2011). Crayfish also were demonstrated to greatly suppress the Bradford Springs population of Ash Meadows speckled dace population (McShane and others, 2004). Red-rim melania is known to displace native snail populations (Mitchell and others, 2007), and has been implicated as an agent of extinction of native Ash Meadows spring-snails (Donald Sada, Desert Research Institute, oral commun., 2011). Both invasive invertebrates are difficult to control or eradicate (Mitchell and others, 2007; Freeman and others, 2010).

Habitat restoration that favors native species can help control non-native species (McShane and others, 2004; Scoppettone and others, 2005; Kennedy and others, 2006). Restoration of Carson Slough and its tributaries present an opportunity to promote habitat types that favor native species over non-natives. Historically, the majority of Ash Meadows spring systems were tributaries to Carson Slough. In 2007 and 2008, a survey of Ash Meadows spring systems was conducted to generate baseline information on the distribution of fishes throughout AMNWR (Scoppettone and others, 2011b). In this study, we conducted a follow-up survey with emphasis on upper Carson Slough. This permitted us to gauge the early effects of spring system restoration on fish populations and to generate further baseline data relevant to future restoration efforts.