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Distribution, habitat use, and relative abundance of the rare razorback sucker Xyrauchen texanus were evaluated by the capture of 323 of the fish and by the use of radiotelemetric data from six fish. Razorback suckers in the Green River were not uniformly distributed; they were most abundant in flat‐water sections, and none were collected in white‐water canyons. Razorback suckers displayed spawning movements in spring, and three spawning reaches were identified by the collection of 101 fish in breeding condition. Larval razorback suckers were collected downstream of the spawning reaches, but no juveniles were collected, indicating little or no successful recruitment. Spawning preferences were deduced from the capture of 52 ripe razorback suckers, between May 3 and June 15, 1984, and between April 22 and June 5, 1986, over sand and gravel substrates. Water temperatures at the points of capture ranged from 10 to 18°C, averaging 15°C. Catch data suggested that the razorback sucker population is small, and that the species is more rare than the endangered Colorado squawfish Ptychocheilus lucius. Low numbers, little growth, and no apparent recruitment suggest that this species will disappear in nature as old fish die and are not replaced.

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