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Biological Environment <br />Extensive bottomland habitats in this reach are sources of nutrient inputs into the Green <br />River and provide food for razorback sucker. Additionally, historical Yampa River levels of <br />nutrients are maintained. This portion of the Green River also contains large numbers of red <br />shiner, channel catfish, black bullhead, green sunfish, and common carp, all of which are <br />known to compete with and/or prey upon native fishes. Other piscivorous fish species in this <br />reach include Colorado squawfish, northern pike, and walleye. <br />Relationship to Additional Selection Criteria: <br />For the razorback sucker, additional selection criteria were developed to assist in the <br />selection of proposed critical habitat designations. This reach of the Green River meets those <br />criteria. <br />Presence of Spawning Population <br />Adults in spawning condition have been captured at Echo Park, Old Charley Wash, lower <br />Ashley Creek, the mouth of the Duchesne River, the Stewart Lake Drain, and areas in <br />between (Tyus and Karp 1990). <br />Nursery Habitat <br />Echo and Island parks and the Jensen area contain numerous backwater habitats for rearing <br />of young fish. Bottomlands at Escalante, Old Charley Wash, and elsewhere may be <br />important nursery areas (Wick 1992). <br />Historic or Present Distribution <br />This reach contains the largest remaining riverine population of razorback sucker (Lanigan <br />and Tyus 1989). Historically, they were much more abundant than at present. Because of <br />lack of recruitment, the number of razorback suckers remaining in this reach continues to <br />decline (Tim Modde, USFWS, pers. comm.). <br />Maintenance of Rangewide Distribution <br />This area is considered the most important riverine reach remaining for the razorback sucker <br />in the Colorado River basin. <br />Special Management <br />The Bureau of Reclamation and the Service have reached an agreement on the operation of <br />Flaming Gorge Dam to provide for some of the flow requirements of the razorback sucker in <br />the Green River. Flow releases are increased in Spring to allow inundation of some spring <br />51