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<br />have been reported from the Grand Canyon, and adults would be able to seek low velocity .
<br />habitats,
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<br />The proposed action will have no affect on the Razorback Sucker,
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<br />HUMPBACK CHUB (Gila r.ypha Miller)
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<br />Species InformatioD
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<br />S1atIa
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<br />The humpback chub (HBC; Cyprinidae: Gila ~ is an endemic fish species in the Colorado
<br />River basin, The humpback chub was listed as an endangered species by the U,S. Fish and
<br />Wildlife Service (Service) on March 11, 1967 (32 FR4001), The species is under protection of
<br />the Endangered Species Act of 1973 (Public Law 97-304), as amended, A recovery plan was
<br />approved on August 22, 1979, and revised on May 15, 1984 (U,S, Fish and Wildlife Service
<br />1990), Critical habitat was designated for the humpback chub and three other Colorado River
<br />fishes (i.e" Colorado squawfish, razorback sucker, bonytail) on March 21, 1994 (59 FR 13374):
<br />The Service designated seven reaches in the Colorado River Basin as critical habitat for humpback
<br />chub, for a total of379 miles. This represents about 28% of the historic range of the species and
<br />includes portions of the Colorado, Green, and Yampa rivers in the upper basin, and the Colorado
<br />and Little Colorado (LCR) rivers in the lower basin. Critical habitat in the lower basin is entirely
<br />within Marble and Grand canyons and includes the Colorado River from Nautiloid Canyon (RM
<br />34; i.e" distance downstream from Lees Ferry) downstream to Granite Park (RM 208), and the
<br />lower 8 miles of the LCR
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<br />Description
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<br />The humpback chub is a large river cyprinid (minnow) endemic to the Colorado River Basin, It
<br />was first described from specimens taken in Grand Canyon, Arizona (Miller 1946), It is
<br />characterized by a prominent; rounded nuchal hump behind the head, which first fonns in juveniles
<br />and becomes more pronounced as the fish mature and age. The head is small, flattened or
<br />depressed on top, and the mouth is overhung by a fleshy snout. The body is deep and Iatera11y ,
<br />compressed, and tapers rapidly to a long, slender tail ( caudal peduncle) with a deeply forked tail
<br />fin. The color is typically dull grayish-green on the back, silvery sides, and fading to a white belly,
<br />Spawning adults in March~lune are tinged with rosy red on the gill covers, pectoral and pelvic
<br />tins, and belly. Spawning adults also have small pimple-like tubercles on the head and fins, There
<br />are usually 9 principal dorsal tin rays and 10 principal anal tin rays, Scales are deeply embedded
<br />and absent from the nuchal hump, with about 80 in the lateral line, Scales above the lateral line
<br />are deeply embedded and, for the most part, completely isolated from one another, The
<br />pharyngeal arch is small with a short lower ramus, and the tooth pattern is usually 2,5-4,2,
<br />Maximum recorded body size is about 480 mm TL and 1,165 g (Valdez and Rye11997),
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