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Last modified
1/26/2010 3:15:34 PM
Creation date
10/12/2006 4:39:09 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.101.09
Description
Glen Canyon Dam/Lake Powell
State
AZ
Basin
Colorado Mainstem
Date
12/21/1994
Author
USDOI-USFWS
Title
Final Biological Opinion-Operation of the GlenCanyon Dam as the Modified Low Fluctuation Flow Alternative of the Final Environmental Impact Statement-Operation of Glen Canyon Dam
Water Supply Pro - Doc Type
Biological Opinion
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<br />Physical Habitat - This includes areas of the Colorado River system that are inhabited <br />by fish or potentially habitable for use in spawning, nursery, feeding, and rearing or <br />corridors between these areas~ In addition to river channels, these areas also include' <br />bottomlands, side;channels, secondary channels, oxbows" backwaters, and other areas in <br />the lOO-year floodplain, which when inundated provide spawning, nursery, feeding, and <br />rearing habitats. <br /> <br />Biological Environment - Components of this element include food supply, predation, and <br />competition. . Food supply is a function of nutrient supply, productivity, and availability <br />to each life stage of the species. Predation and competition, although a normal <br />component, may be out of balance because of non-native fish species. <br /> <br />RAZORBACK SUCKER <br /> <br />General Status <br /> <br />The razorback sucker was listed as an endangered species throughout its range on October 23, <br />1991 (U.S. Fish and Wildlife Service 1991b). Once one of the most abundant and widespread <br />fishes of the mainstem rivers in the Colorado River Basin, successful recruitment to adult of this .. <br />monotypic genus is now virtually nonexistent in all natural riverine environments (reviewed in <br />Mincldey et al. 1991; U.S. Fish and Wildlife Service 1991b). Archaeological and historical <br />information reported by the above reviewers identified lower basin records of razorback suckers <br />in Arizona in the San Pedro River, the Gila River near Phoenix, the upper Verde River, <br />Colorado River near Lee's Ferry, and the Salton Sea (California) and Colorado River delta <br />(Mexico). Historic range in Arizona includes all of the mainstem Colorado River, most of the <br />Verde River and San Pedro River, the lower portion of the Salt River, and almost the entire Gila <br />River (Mincldey et al. 1991). <br /> <br />The razorback sucker now inhabits about 25 % of its former range, and of the four "big river" <br />endangered fish, only the bony tail chub is believed to be more rare (U.S. Fish and Wildlife <br />Service 1991b). In the upper basin,the species persists in the San Juan and Colorado River <br />arms of Lake Powell, the Grand Valley area of the Colorado River, and the lower Yampa River <br />and Green River, with the largest concentration in this last area. In the lower basin, the <br />formation of Lake Mohave on the Colorado River in 1954 retained a large number of razorback <br />suckers that now comprise the largest population of the species which Marsh and Mincldey <br />(1992) estimated at approximately 60,000. Mincldey et al. (1991) report that limited numbers <br />of razorback suckers have been. found in Lake Havasu, the Central Arizona Project aqueduct <br />(near the Lake Havasu intake), and from the Colorado River downstream of Parker Dam in <br />irrigation ditches and in Senator Wash Reservoir but that an approximate lO-year reintroduction <br />program in central Arizona rivers has had little success. <br /> <br />Mincldey (1983) reported that:18 .razorback suckers were recorded~by investigators at various <br />localities in Lake Mead from: 1967 to 1980, and in 1990 Jon Sjoberg (Nevada Department of <br />Wildlife, personal communication) reported sighting and capturing small numbers of razorback <br />suckers in westem'Lake Mead. Using helicopters to locate aggregations, 36.razorback suckers <br />in western Lake Mead were captured and tagged in 1992 (Heinrich and Sjoberg 1992; Burke <br /> <br />IS December 1994 nnal biological opinion 1-21-93-F-167 <br /> <br />12 <br />
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