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1 <br /> <br /> <br /> <br />1 <br />1 <br /> <br /> <br />f? <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br />imbedded scales indicate this species is a more specialized divergence from G. <br />robusta. These adaptations may provide an advantage in swift water <br />environments, and small eyes and a terminal mouth may have been adapted as a <br />result of the high sediment load of the Colorado River system (Minckley 1973). <br />Adult bonytail were usually found in eddies and pools near swift <br />currents over silt and boulder substrates (Vanicek and Kramer 1969; Valdez <br />1985). Chart and Cranney (1993) found adult bonytail in zones of mixing water <br />between eddies and runs, whereas humpback chub occupied deep canyon eddies. <br />Since G. elegans are not discernable from other Gila species at 200 mm <br />total length (TL) and smaller, no conclusions can be made about the specific <br />ecology of subadult bonytail in the wild (Vanicek 1967). Most immature Gila <br />have been caught in low velocity, sheltered habitats over silt or occasionally <br />rubble. At age three, however, Vanicek (1967) noted that young bonytail grew <br />faster in length, and roundtail chub grew larger in weight indicating bonytail <br />are longer and leaner, whereas roundtail chub are shorter and heavier. <br />Chart and Cranney (1993) detected diel movement patterns in bonytail <br />with peak activity occurring during crepuscular periods. Seasonal changes in <br />activity were also evident. In winter, peak movement occurred during mornings <br />and the fish were less active overall. Most gross movement occurred in a <br />general downstream direction. The bonytail that survived through the duration <br />of the study eventually remained in localized areas. Also, high discharge <br />appeared to be correlated with greater movement (Chart and Cranney 1993). <br />In the laboratory, Berry and Pimentel (1985) found that although <br />bonytail were better swimmers than Colorado squawfish (Pytochocheilus lucius), <br />bonytail swimming ability was comparable to many other freshwater fish. <br />Bissonette and Crowl (1995) tested velocity and substrate preferences of age-1 <br />fish in a laboratory setting and found that young bonytail exclusively <br />11 <br />I