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<br />000589 <br /> <br />in the birds. <br /> <br />In conclusion, it is believed that removal of nonnative fish species from <br />floodplain ponds along the Upper Colorado and Gunnison rivers would not <br />cause a significant adverse impact on fish-eating birds because alternate <br />feeding areas are available adjacent to the floodplains where ponds would <br />be reclaimed. Removal of nonnative fish species from some floodplain ponds <br />along the Upper Colorado and Gunnison rivers will not result in complete <br />e 1 i mi nat i on of small fi sh that serve as food for bi rds . Although there <br />would be a minor negative impact to piscivorous bird species, this would be <br />offset with a pos it i ve impact of increased aquat i c invertebrates for <br />shorebirds and waterfowl. <br /> <br />Endanqered Species. Food supplies for young life stages of the endangered <br />fi shes, duri ng the crit i ca 1 peri od when high mortality can occur, are <br />limited in the main channels of rivers in the Upper Colorado River Basin <br />(Wydoski and Wick 1996). Zoopl ankton used for' food by newly hatched <br />endangered fishes are more abundant in backwaters and embaymentsconnected <br />to the river and most abundant in flooded bottomland habitats (Cooper and <br />Severn 1994a, b, c, d; Mabey and Sch i ozawa 1993). However, nonnat i ve fi sh <br />species in such habitats prey on and compete with the young life stages of <br />the endangered fishes. . <br /> <br />Osmundson (1986) found that endangered fishes in riverside ponds along the <br />Colorado River survived and grew well in .ponds free of nonnative fishes. <br />Reclamation of floodplain ponds would remove the potential of predation and <br />competition by nonnative fish species that occurs to young endangered fishes <br />in the backwaters and embayments of the rivers. Reclaimed floodplain ponds <br />would be excellent grow-out facilities for captive-reared endangered fishes <br />prior to release into the rivers of the Upper .Colorado River Basin <br />(Osmundson and Kaeding 1989). <br /> <br />Surveys of floodplain ponds in the Upper Colorado River for Colorado <br />squawfish and razorback suckers in the late 1980's were negative. Only one <br />private pond near DeBeque, Colorado contained razorback suckers that were <br />the offspring of several razorbacks that were stranded after the 100-year <br />floods of 1983 or 1984 receded. However, surveys will be conducted prior <br />to chemical treatment to check for endangered fishes with gears such as <br />electrofishing, trammel nets, and trap nets. Although there is a <br />possibility that an endangered fish in a floodplain pond could be killed by <br />the chemical treatment, it is not anticipated that many (perhaps one or two) <br />endangered fish would be killed through the proposed action. The benefits <br />to endangered fi sh recovery are bel i eved to be greater than the remote <br />poss i bil ity of kill i ng one or several endangered fi sh duri ng chemi ca 1 <br />treatment. <br /> <br />Powdered rotenone to be used in chemical treatment of floodplain ponds would <br />be applied carefully so that drift of the powder is controlled and confined <br />to the target area. Since rotenone is toxic to terrestrial insects that are <br />used as food by endangered species such as the Southwestern willow <br />flycatcher, extra precautions will be taken to prevent treatment of <br />nontarget areas. <br /> <br />20 <br />