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WSP11688
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Last modified
1/26/2010 3:18:31 PM
Creation date
10/12/2006 5:06:38 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.104.I
Description
Flaming Gorge
State
UT
Basin
Yampa/White/Green
Date
11/25/1992
Author
USDOI-USFWS
Title
Final Biological Opinion on the Operation of Flaming Gorge Dam - (Part 1 of 2)
Water Supply Pro - Doc Type
Biological Opinion
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<br />} <br /> <br />18 <br /> <br />In Dinosaur, humpback chub spawn in spring and early summer fallowing highest <br />spring flows at river temperatures about 20 .C (Karp and Tyus 1990a). This <br />included Hay and June in low (e.g., 1987 and 1989) and average (e.g., 1988) <br />flow years but extended into July during the 1986 high-flow year. Ripe fish <br />are predominantly captured in shoreline eddy habitats in the upper 30 miles of <br />Yampa Canyon, and there is some indication that these fish remain in or near <br />specific eddies for extended periods and return to the same eddy during the <br />spawning season in different years (Karp and Tyus 1990a). It is unknown where <br />humpback chubs deposit eggs, but the use of shoreline eddies that are <br />associated with boulder/sand substrates is considered important to the <br />breeding requirements of humpback chub in Dinosaur. Availability .of shareline <br />eddy habitat is greatest with spring flooding and decreases thereafter with <br />decreasing summer flows; these habitats are formed and maintained by spring <br />runaff. Loss .or reduction of spring runoff could reduce availability of <br />spawning habitat and consequently adversely affect humpback chub reproduction. <br />Habitat alternation also may promate hybridization with other species (Valdez <br />and Clemmer 1982). Flow reductions (absence of spring peak) and decreased <br />temperatures were implicated as factors curtailing successful spawn and <br />increasing competition in the Colorado River (Kaeding and Zimmerman 1983). <br /> <br />Larval and Juvenile <br /> <br />Larval and yaung-of-year humpback chub are generally found in law velacity <br />microhabitats associated with backwaters and eddies. Fish graw from 7.5- <br />10.5 cm during their first year of life, and by age-2 many are 200 mm <br />(8 inches). Hales begin reaching sexual maturity at age-2 and females at <br />age-3. Once humpback chubs reach sexual maturity growth slows considerably. <br /> <br />BONYTAIL CHUB <br /> <br />status and Distribution <br /> <br />Historically, the bony tail chub occurred thraughout the Colorado River main <br />stem and its major tributaries, including the Gila and Salt Rivers in the <br />lower basin and the Green, Yampa, White, Gunnison, and San Juan Rivers in the <br />upper basin. Recent collections indicate the fish is extremely rare and is <br />extirpated from much of its former range, although individual fish are still <br />occasianally collected from the upper and lower basins. Supplemental stacking <br />from hatchery fish and maintaining stocks in hatcheries may be necessary to <br />preclude this species from becoming extinct. The recovery goal for bony tail <br />chub (U.S. Fish and Wildljfe Service 1990b) is to .prevent immediate <br />extinction.. <br /> <br />Adults <br /> <br />Habitat requirements of the bony tail chub in the Green River basin are little <br />known. Fish collections in Echo Park (Dinosaur) before and after closure of <br />Flaming Gorge Dam indicated that the species was present in moderate numbers <br />at the confluence of Yampa and Green Rivers (Vanicek 1967). But, more recent <br />investigations in that area yielded few captures. Holden and Stalnaker (1975) <br />reported the capture of 36 bony tail chubs in Yampa (lower 10 miles) and upper <br />Green Rivers from 1968 to 1970. Holden and Crist (1981) collected one <br />
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