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<br />>"'" <br />"""'~ <br />~i;-"',?' <br /> <br />mainstream habitats in the Lower Colorado River exceed 900F (Dill 1944). <br /> <br />~' <br /> <br />RBS diet varies by age class and habitat type, but few data are available on <br />the diet of larval and juvenile RES (Bescgen 1990). Larval RES are known to <br />feed on phytoplankton and zooplankton, and (in fluvial habitats) on chironomid <br />larvae. Adult RES in 1entic habitats feed on benthic and planktonic algae and <br />macroinvertebrates, while adult RBS in rivers feed primarily on benthic algae <br />and invertebrates. <br /> <br />" <br /> <br />RBS spawn earlier in the season than do most other native, warm water Colorado <br />River fish (Minckley 1973, 1991). Lake Mohave RES spawn from November into <br />May, with the peak of spawning activity between January and March when water <br />temperatures were stable (50 to 540F) or rising from 50 to 590F (Bozek et al., <br />1984). In riverine situations in the Upper Basin, RBS begin spawning on the <br />rising limb of the spring (April-May) hydrograph, and spawn for an extended <br />period through the spring runoff. Although it occurred throughout the day, <br />spawning activity is most intense at dusk. <br /> <br />; <br />f~ <br /> <br />c" <br />~~ <br /> <br />RES are susceptible to parasitic bacteria, protozoa and copepods. Minckley <br />(1983) and others have reported a high incidence of blindness in one or both <br />eyes; however the reasons for this condition are not clear (Bestgen 1990) . <br /> <br />~; <br />"- <br />~ <br />,,~ <br />~, <br /> <br />", <br />" <br />rti <br />\~ <br /> <br />Impacts of the test flow <br /> <br />" <br />!~, <br /> <br />The test flow will have no effect on the remaining RBS population in the <br />Colorado River in Grand Canyon. Remaining RBS are mature or senile fish, <br />which survived comparable or higher mainstream flows in 1965, 1973, 1980, and <br />1~83-1~86, and possibly during the pre-dam era. The older fish are capable of <br />finding suitable refugia, and the lack,of recruitment of this species <br />indicates that no young razorback sucker are in the system or at risk during <br />the test flow. Because RES spawn somewhat earlier than HBC, the early date of <br />the test flow may stimulate some additional RBS spawning activ~ty. <br /> <br />h~ <br />;;~ <br />f.', <br /> <br />" <br />,. <br /> <br />r-" <br /> <br />~,., <br /> <br />L <br /> <br />BALD EAGLE SPECIES ACCOUNT <br /> <br />~;" <br />"-\I <br />:$" <br />~':'-" <br />f]i; <br />11:': <br />~";, I <br />1s~~ ' <br />,'\ <br />f.!:~ <br />i:~~ <br />,;-;: <br />~ <br />t <br />~:? ' <br />f:~.~ <br /> <br />Distribution and Abundance <br /> <br />The bald eagle (Accipitridae: Haliaeetus leucocechalus) has suffered <br />population declines from habitat loss, mortality from shooting and poisoning, <br />and reduced reproductive success from ingestion of contaminants (U.S. Fish and <br />Wildlife Service 1983), and it was recognized as a threatened and declining <br />species in 1967. This species occurs throughout North America from Alaska to <br />northern Mexico, and commonly breeds in the northern portion of its range <br />(Stahlmaster 1987). Although bald eagles face numerous threats throughout the <br />48 states, they have recovered from dramatic population declines over the past <br />several decades. Consequently, the U.S. Fish and Wildlife Service downlisted <br />the bald eagle from endangered to threatened status (U.S. Fish and Wildlife <br />Service 1995) . <br /> <br />, ~, <br /> <br />12 <br />