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The endangered humpback chub (Gila c ha is an especially adapted <br />omnivore which prefers to inhabit deep turbulent canyon reaches. The fleshy <br />hump on its back resembling the leading edge of an airplane wing is thought <br />to be an adaptation to assist in holding position in fast turbulent currents such <br />as the habitat in the Grand Canyon (Valdez and Ryel 1995). <br />The endangered bonytail chub (Gila ele ans is very streamlined with <br />a distinctively narrow caudal peduncle. Bonytail inhabit both confined and <br />unconfined river reaches and appear to prefer environments also favored by <br />razorback sucker. Very little information about the bonytail chub's life <br />history was obtained prior to its rapid decline throughout the river system. <br />Other endemic, big-river species in danger include the roundtail chub <br />t Gila robust a), an omnivore most commonly found in mid-size tributary <br />f_ <br />rivers. The flannelmouth sucker (Catostomas lati inus inhabits both tributary <br />streams and larger river environments. The flannelmouth sucker is <br />characterized by very large protruding fleshy lips with numerous papilla <br />which assist it in feeding on bottom detritus, its specialty. The bluehead <br />sucker (Catostomus discobolus), a native also found in a small part of the <br />Bonneville basin, has a special blade-like structure on it's lower jaw that <br />functions as a scraper, enabling this species to scrape food items from green <br />algal colonization on rock substrates (Miller 1964). Bluehead sucker are <br />commonly collected in big rivers from swift riffle areas with rock substrate. <br />Razorback fills the floodplain niche <br />The razorback sucker (Xvrauchen texanus) is an endemic genus and <br />species specially adapted for filter feeding on zooplankton in lentic <br />environments. The genus (Xvrauchen) is closely related genetically to the <br />genus (Catatomus) indicating rapid morphological evoluton into a new niche. <br />( R. Behnke, pers. comm.). The close ralationship between these two genuses <br />is also evident by hybridization. <br />°t 8