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<br />In the, Grand Canyon area, razorback: suckers rarely, have been collected. Carothers and <br />Minckley (1981) collected one and observed three in or near the Paria River (1978-1979). A <br />razorback -sucker WaS collected.in and released. near RM 1 08 in' the mainstem (1984 ) and, at the <br />mouth of the LCR, one was captured in 1989 and five were PIT tagged in 1990 (Dennis Kubly, <br />Arizona Game and Fish Department, personnel communication). <br /> <br /> <br />1992).. No razorback suckers were reported from a 1991 survey of selected locations in eastern <br />Lake Mead (Baucom 1991). <br /> <br />t";' <br /> <br />Adults <br /> <br />.:" <br /> <br />Because adult razorback suckers are the second largest native fish in the Colorado basin, average <br />total length in Lake Mohave was 550 mm for males and 620 mm for females (Marsh and <br />Minckley.1992), it has been feasible to implant them with radio or ultrasonic transmitters to <br />track movements and habitats utilized. Marsh and Minckley (1991) found radio-tagged <br />individuals transplanted to the Gila River above San Carlos Reservoir, Arizona to use mid- <br />channel habitats that were wide runs with sand substrate. Quieter habitats such as backwaters, <br />eddies, and deep pools were selected by few fish. Radio-tagged razorback suckers (Tyus 1987) <br />used the mid-channel sand bars of the flat-water reaches of the upper Green River' and lower <br />Duchesne River in summer rather than deep pools. Velocities of these habitats were slow (0.5 <br />m/s) and depths were about 1.5 m. Of the over 300 razorback suckers captured in the Tyus <br />study, none used the white-water canyon reaches. A study of reintroduced adult and subadult <br />razorback suckers radiotracked in the upper Verde River, Arizona, found these fish occupied <br />habitats with slower mean current velocity (0.03 m/s) and shallower mean depths (0.72 m) than <br />reported from upper basin studies; however, in both studies, preference for sand substrates was <br />similar (Clarkson et aI. 1993). Two of the Verde River radiotagged suckers moved more than <br />60 km downstream after reintroduction. <br /> <br />,_f,_ <br /> <br /> <br />"--; <br /> <br />,-;.~.." <br /> <br />Recollections of first-hand observers from the early 1900's, reported by Minckley (1973) and <br />Minckley et aI. (1991), w.ere that razorback suckers were in eddies, backwaters, or deep holes <br />and were sometimes fished by snagging. Holden and Stalnaker (1975) in a study of the <br />Colorado River from the upper Yampa and Green Rivers down to men Canyon, Marble <br />Canyon, and Grand Canyon on the Colorado River found razorback suckers only in "stagnant <br />or quiet-water areas." They identified one concentration site as wash conflUences during high <br />water of early summer in Canyonlands National Park. Bestgen (1990) remarked on the greater, <br />perhaps even year-round, use of lentic and backwater habitats by razorback suckers compared <br />to the other "big river" fishes. Further evidence of this apparent preference for "quite-water" <br />may be the success in raising and maintaining razorback suckers in ponds and lakes that has been <br />observed by many who work with the species. <br /> <br />j~{ <br />~-.;< <br />"." <br />it": <br /> <br />tlt <br />~': <br />i;>t <br />~~~ <br />r~1 <br />~~ <br /> <br />Minckley (1991}described-the different adaptations to feeding. for the three native Grand Canyon <br />suckers and .stated .that the:razorback,sucker..possessa ."protrusible mouth and special gill rakers <br />for sieving. plankton or detritus." Marsh, (1987) examined stomachs (n=32) of adulrrazorback <br />suckers and found planktonic crustaceans, diatoms, filamentous algae,. and detritus demonstrating <br />feeding occurs both on plankton and benlhic organisms. Dill (l944):found razorback sucker <br /> <br /> <br />IS December 1994 fmal biological opinion 2-21-93-F-167 <br /> <br />13 <br />