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Page 20 Species Overview The three fish species are all in the order Cypriniformes. Roundtail chub (Figure 2-3) are in the family Cyprinidae, the minnows. Flannelmouth sucker (Figure 2-4) and bluehead sucker (Figure 2-5) are in the family Catostomidae, the suckers. Common characteristics of endemic, large-river fish including the three fish species, are: 1) fusiform bodies, 2) humped or keeled dorsal surfaces (only present in the endangered Colorado River species, not the three species), 3) leathery skins with embedded scales, and 4) large, often falcate, fins. Such morphological Fi2:ure 2-3 Adult roundtail chub (Gila robusta) features, combined with relatively long life spans, are thought to be adaptations to the harsh, unpredictable physical environment of the Colorado River Basin (Bezzerides and Bestgen 2002, Minckley 1991, Scoppettone 1988, Steams 1993). All three species reach relatively large sizes (ca. 300 - 500 mm), are relatively long- lived, and are thought to require only sporadic recruitment to maintain population stability. Of the three fish species, tlannelmouth sucker can demonstrate long-range movement (ca. hundreds of stream miles) ili!oughout the course of their lives, which is not generally observed for the other two species (Bezzerides and Bestgen 2002). The two catostomids are primarily benthic feeders (Banks 1964; Childs et al. 1998; Grabowski and Hiebert 1989; Greger and Deacon 1988; Minckley 1973; Muth and Snyder 1995), whereas adult roundtail chub are frequently omnivorous and can be piscivorous and insectivorous as large juveniles and adults (Bestgen 1985; Karp and Tyus 1990; Koster 1957; McDonald and Dotson 1960; Neve 1976; Schreiber Figure 2-5 Adult bluehead sucker and Minckley 1981; Rinne 1992; Tyus and Minckley (Catostomus discobolus) 1988; Vanicek and Kramer 1969). Additional life history characteristics, distribution and abundance have been described in numerous texts and publications for roundtail chub (Bestgen and Propst 1989, Brouder et al. 2000, Voeltz 2002), tlannelmouth sucker (Chart 1987, Douglas and Marsh 1998, McKinney et al. 1999), and bluehead sucker (e.g., Bestgen 2000, Cavalli 1999, Holden and Minckley 1980, McAda 1977, McAda and Wydoski 1983). Bluehead sucker are also discussed in Brunson and Christopherson (2001), Jackson (2001), Mueller et al. (1998), and Valdez (1990). Figure 2-4 Adult flannelmouth sucker (Catostomus latipinnis) Flannelmouth and bluehead sucker have most often been recorded in large rivers, though tributary occurrences are often observed for both species (McAda et al. 1977; Fridell et al. 2004; Morvilius and Fridell 2005; Walker and Hudson 2004; Walker and Birdsey 2005). It is currently thought that they also use tributary streams for one or more life history stages (Maddux and Kepner 1988, Weiss et al. 1998). In the past, roundtail chub were observed inmainstem habitats. Today; they are much