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The population of endangered razorback suckers Xyrauchen texanus in the middle Green River (upper Colorado River basin) has declined during the last 40 years. The apparent cause for this decline is a lack of successful recruitment. This study used radiotelemetry to evaluate the ability of hatchery-reared razorback suckers to locate spawning areas where wild fish congregate during the ascending hydrographic limb of the snowmelt runoff. Hatchery-reared razorback suckers appeared to show similar reproductive behavior to wild fish. Both wild and hatchery-reared fish were found near the middle Green River spawning area between 1 and 25 May 2000. Hatchery fish occupied the same areas on the spawning site as wild fish,...
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This report represents a river reach application of the reset concept to examine survival and growth of larval razorback sucker and bonytail in floodplains. The floodplain reset concept refers to eliminating residual fish populations from floodplains prior to their connection to the river during spring flood flows. Despite drought conditions, sufficient river flows allowed the evaluation of the reset concept to enhance larval razorback sucker Xyrauchen texanus and bonytail Gila elegans survival during 2003-2004. Species composition in study floodplains shifted from communities dominated by riverine species to to those preferring lentic conditions following recruitment within floodplains. The number, biomass, and...
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Twelve wild adult Colorado pikeminnow (Ptychocheilus lucius), captured in the tailwaters of Taylor Draw Dam on the White River, Colorado, were implanted with radio transmitters and their movement patterns monitored from 1992 to 1994. The spawning migration of these fish was extensive. In 1993, the only full year of the study, the fish migrated an average of 658 km from the White River to spawning sites in the Yampa or Green rivers and back to the White River. Eight of these fish were translocated in the river upstream of the dam in April 1993. These fish and the 4 others below the dam remained in the river until May 1993. All 12 had migrated down the White River to spawning sites in the Green and Yampa rivers by...
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The goal of this study is to define the baseflow needs of endangered fish populations in the Yampa River. The approach taken was to simulate habitat availability associated with several low flow scenarios and relate changes in habitat availability to habitat use by endangered fishes.
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Existing biological information together with a comparison of historical and estimated virgin flow scenarios were synthesized following with reference to the Recovery Implementation Program instream flow review to update the U.S. Fish and Wildlife Services' interim flow recommendations for the Yampa River. Biological information on endangered fish abundance, distribution, and spawing activity, existing fish composition and migratory movement, and ecological concepts related to native fish persistence was integrated to provide the best estimate of flows necessary for the recovery and maintenance of the endangered fishes in the Yampa River and the Upper Colorado River Basin. Flow recommendations were based on the...
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