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<br />Humpback chub <br /> <br />Humpback chub appear to spawn following the seasonal peak flow at <br />temperatures of about 190 C. Seasonally high flows are important in <br />constructing and maintaining shoreline eddy habitats used by humpback chub <br />throughout the year. <br /> <br />Spring Recommendations <br /> <br />Spring peak flows are associated with reproductive activities of all the target <br />endangered species occupying the Yampa River. Spring peak flows of the <br />Yampa River connect floodplain habitats thus providing seasonal bottomland use <br />by endangered fishes in both the Yampa and Green rivers. The decline of <br />razorback sucker may be due to the loss of floodplain habitat in the low gradient <br />reaches of the Green River and Yampa rivers. Evidence also su9gel?ts that high <br />flows impede establishment of exotic fish species, particularly in canyon bound <br />reaches of the Yampa River. <br /> <br />Spring high flows transport sediments and that are delivered downstream to <br />nursery habitat sites for Colorado squawfish in the middle Green River. High <br />flows are also implicated in reducing encroachment of the introduced salt cedar, <br />and exotic plant that competes with native riparian vegetation. Given the needs <br />for high spring flows the Service recommends that existing flows (minus the <br />baseline depletion) be provided for the recovery of endangered fishes in the <br />Yampa River.. <br /> <br />Summer (June 22 - September 22) <br /> <br />Colorado squawfish <br /> <br />A gradual decline in summer flows following spring scouring of cobble <br />substrates provides an environment that facilitates spawning, incubation, larval <br />emergence, and downstream drift of larvae, as well as, enhance growth and <br />development of embryos and larvae. High spring flows help to create <br />downstream nursery areas, but these habitats are maintained as productive fish <br />habitats by declining flows. Sufficient flows are necessary for return migration <br />of postspawning adults past low flow obstacles in the river channel. Variability <br />in flow among years and months should provide greater benefits to native <br />fishes, as observed in Yampa Canyon. <br /> <br />Humpback chub <br /> <br />Extremely low summer flows could adversely affect spawning and nursery <br />habitat of the humpback chub in Yampa Canyon by concentrating fishes in <br />suboptimal habitats and increasing the potential for disease, competition, <br />predation, and hybridization. Variability in flow among years should provide <br />greater benefits to native fishes, as observed in Yampa Canyon. <br /> <br />31 <br />