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salmoides), and Virgin River chub. Spawning observations at Dexter NFHTC, however, <br />indicated little preference for substrates (George Divine, Service, pers. comm., 1994). <br />Deacon and Hardy (1982) and Hardy and Deacon (1982) also found that highest population <br />densities and greatest spawning success occurred in habitats less impacted by water <br />diversions and other habitat modifications. <br />Deacon and Hardy (1982) showed reduced survival of young woundfm at flows below 5.66 <br />m3/sec (200 cfs) although high initial spawning success below the Washington Fields <br />Diversion, near St. George, Utah, at flows less than 0.57 m3/sec (20 cfs) has been noted <br />(Virgin River Fishes Data Base). Deacon and Hardy (1982) also noted that mean monthly <br />flows of 22.66 m3/sec (800 cfs) or higher during the reproductive period resulted in <br />diminished recruitment. Deacon and Hardy (1982) showed that population density and <br />structure were affected by both level of habitat destruction and flow conditions in the river. <br />Reduced recruitment below major diversions has been attributed to water depletions (Deacon <br />and Hardy 1982). These authors also found that when woundfm populations were severely <br />depleted, such as during the 1977 drought, a 2-year period of favorable water conditions was <br />required to rebuild population densities. <br />Little information presently exists on movement of woundfm. Downstream movement within <br />the river by adults and other life stages has been noted (Thomas Hardy and 3ames Deacon, <br />University of Nevada, Las Vegas, unpub. data), but the extent of upstream movement, if <br />any, is not known. <br />Virgia River chub--The Virgin River population of the Virgin River chub was historically <br />found within the mainstem Virgin River from Pah Tempe Springs, Utah, downstream to the <br />confluence with the Colorado River in Nevada (Cope and Yarow 1875, Cross 1975), and in <br />the Muddy River of Nevada. Its current distribution has been reduced to the mainstem <br />Virgin River from Pah Tempe Springs downstream to the Mesquite diversion, and in the <br />Muddy River system upstream of The Narrows [National Biological Survey (NBS) unpub. <br />data, Nevada Division of Wildlife (NDOW) u~ub. data]. <br />Unlike the woundfin, very little information exists on the life history and ecology of the <br />Virgin River chub. Most literature deals primarily with the taxonomy and distribution of the <br />species. Discussions on the taxonomy of Virgin River chub include Cope and Yarrow <br />(1875), Ellis (1914), Snyder (1915), Tanner (1936), Miller (1946), LaRivers and Trelease <br />(1952), Holden and Stalnaker (1970), and Minckley (1973). Information on the distribution <br />of Virgin River chub is documented in Miller (1946), Holden and Stalnaker (1970), <br />Minckley (1973), Cross (1975), Hickman (1985, 1986, 1987x, 1988), and Hardy et al. <br />(1989). Life history and habitat requirements are discussed in La Rivers (1962), Minckley <br />(1973), Deacon and Minckley (1973), Cross (1978), Schumann (1978), Hickman (1987a), <br />and Hardy et al. (1989). Hickman (1987c) compiled an annotated bibliography for the <br />Virgin River chub which contains most of the known publications and government reports <br />dealing with the species. The following life history section summarizes current information <br />concerning the species' habitat, food habits, reproductive biology, and movement. <br />20 <br />