SPAWNING AND MOVEMENTS OF RAZORBACK SUCKER, XYRAUCHEN-TEXANUS, IN THE GREEN RIVER BASIN OF COLORADO AND UTAH

Spawing and movements of the razorback sucker, Xyrauchen texanus, were evaluated by radiotelemetry (n = 17 fish) and capture of 230 adults (105 recaptures) in the Green and Yampa rivers, 1987 to 1989. Ripe fish (n = 194) were captured in riffles with cobble, gravel, and sand substrates from mid-April to early June. Recaptured males were ripe from 2 to 28 days and recaptured females from 2 to 15 days. Razorback suckers spawned during ascending and highest spring flows at water temperatures of about 14-degrees-C (range of 9 to 17-degrees-C). Spawning migrations of 30 to 106 km were detected in 17 razorback suckers, but movements were more limited or undetected in other individuals. Flooded lowlands and lower portions of tributary streams presumably served as resting-feeding areas for razorback suckers during the breeding season. Native flannelmouth suckers (Catostomus latipinnis), bluehead sucker (Catostomus discobolus), and putative flannelmouth x razorback sucker hybrids in breeding condition were collected with ripe razorback suckers. Razorback sucker is in peril due to a paucity of spawning adults, hybridization with other suckers, little or no recruitment, and habitat loss.