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<br />. <br /> <br />. <br /> <br />River due to operations of Flamin9 Gorge Dam may be associated with a loss <br />of effective recruitment to the juvenile stage. Normal seasonal inundation <br />of low-lying lands provides a food base for adults and may be important for <br />future dispersal and rearing of young. Unless higher, warmer flows can be <br />released from Flaming Gorge Dam than are presently occurring with current <br />operations, such seasonal flooding can only be accomplished by flows of the <br />Yampa River. <br /> <br />Humpback chub <br /> <br />Spawning of humpback chub occurred shortly after highest spring discharge at <br />temperatures of about 19.5C (range 14.5-23C) in 1987-1989. These flows are <br />also important to promote development of shoreline eddy habitat used by the <br />fish, and deepening of habitats used later in the year. Interspecific <br />hybridization between chubs may result from alterations of historic <br />conditions during spawning. <br /> <br />SprinQ recommendations <br /> <br />Spawning migrations of Colorado squawfish and razorback suckers require free <br />channel access in their occupied Yampa River range. Uninterrupted flow (no <br />stream blockage without proven fish passage capabilities) should be <br />maintained in the Yampa River from its mouth to Craig, Colorado. <br /> <br />Spring peak flows are associated with reproduction of all the target fish <br />species, and this occurs with ascending (razorback sucker), peak (Colorado <br />squawfish), and descending (humpback chub and Colorado squawfish) flows. <br />Spring peak flows of the Yampa River provide seasonal bottomland habitats, <br />and maintain Colorado squawfish nursery habitats. The loss of razorback <br />sucker recruitment may be related to a reduction of flooded lands. Because <br />all approved projects in the Yampa River are not yet fully operational, it <br />is anticipated that some additional change in these flows and associated <br />effects on the aquatic environment will occur as the environmental baseline <br />flows are implemented. The environmental baseline includes all existing <br />projects, and all projects which have received favorable opinions under <br />Section 7 consultation but are not yet operating (Table 3). Loss of natural <br />spring peaks due to flow regulations were associated with decline or loss of <br />native fish populations in the upper Green, San Juan, and lower Colorado <br />rivers. <br /> <br />High flows are also implicated in restricting the growth of the introduced <br />salt cedar (Tamarix ramosissima), an exotic plant that competes with native <br />riparian vegetation (e.g., cottonwood and willow) and alters important <br />riparian habitat via shoreline stabilization. Changes brought by this plant <br />are not conducive to providing good humpback chub spawning habitat. There <br />is also evidence that high spring flows limit the proliferation of fish <br />species introduced from more mesic environments, while little affecting the <br />more adapted native fish community. <br /> <br />High spring flows mobilize sediments that are delivered to downstream areas, <br />and provide the basis for creating nursery habitat for Colorado squawfish in <br />the upper Green River. Native fishes are adapted to this high sediment <br />load, and the resultant turbidity presumably reduces the efficiency of more <br />visually dependent predators, such as northern pike and walleye. <br /> <br />4 <br />