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Dinosaur National Monument as the highest priority for stocking in Colorado and the . <br />plan calls for 2,665 fish to be stocked per year over the next 6 years (Kesler et al. 2003). <br />Threats to the species include stream flow regulation, habitat modification, predation by <br />introduced nonnative fish species, hybridization, and pesticides and other pollutants <br />(USFWS 2002d). <br />Threats to the Species <br />The primary threats to bonytail are stream flow regulation and habitat modification; <br />competition with and predation by nonnative fishes; hybridization with other native Gila <br />species; and pesticides and pollutants (USFWS 2002d). The existing habitat, altered by <br />these threats, has been modified to the extent that it impairs essential behavior patterns, <br />such as breeding, feeding, and sheltering. The threats to bonytail in relation to flow <br />regulation and habitat modification, predation by nonnative fishes, and pesticides and <br />pollutants are essentially the same threats identified for Colorado pikeminnow. Threats <br />to bonytail in relation to hybridization are essentially the same threats identified for <br />humpback chub. <br />Life History <br />The bonytail is considered a species that is adapted to mainstem rivers, where it has been <br />observed in pools and eddies (Vanicek 1967; Minckley 1973). Spawning of bonytail has <br />never been observed in a river, but ripe fish were collected in Dinosaur National <br />Monument during late June and early July suggesting that spawning occurred at water <br />temperatures of about 18 °C (Vanicek and Kramer 1969). Similar to other closely related <br />Gila species, bonytail probably spawn in rivers in spring over rocky substrates; spawning <br />has been observed in reservoirs over rocky shoals and shorelines. <br />Population Dynamics <br />Bonytail are so rare that it is currently not possible to conduct population estimates. A <br />stocking program is being implemented to reestablish populations in the upper Colorado <br />River basin. From 1996 through 2004, 44,472 subadult bonytail were stocked in the <br />Green and upper Colorado River subbasins. The Recovery Goals (USFWS 2002d) call <br />for reestablished populations in the Green River and upper Colorado River subbasins, <br />each with >4,400 adults that are self-sustaining with recruitment. <br />Critical Habitat <br />Critical habitat was designated in 1994 within the bonytail's historical range in the <br />following sections of the upper Colorado River (59 FR 13374). The PCEs are the same <br />as those described for the Colorado pikeminnow, as is the status of the PCEs. We <br />designated seven reaches of the Colorado River system as critical habitat for the bonytail <br />chub. These reaches total 312 miles as measured along the center line of the subject <br />reaches, representing approximately 14 percent of the historical habitat of the species. <br />Critical habitat includes portions of the Colorado, Green, and Yampa Rivers in the Upper <br />Basin: <br />26