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<br />Proposed Water Year 2005-2006 Experimental Actions <br /> <br />01818 <br /> <br />11 <br /> <br />High Experimental Flow <br /> <br />Valdez and Ryel (1995) reported that adult and juvenile HBC found in the mainstream <br />utilize deeper eddies in the fall and winter period (approximately late October through <br />February), therefore they may be less affected by a short duration high flow of the <br />proposed magnitude, Young-of-year HBC emerging from the Little Colorado River may <br />suffer mortality as a result of the high flow event, but monsoonal floods that would <br />transport them into the mainstream largely have ceased by the end of October. The <br />mortality of young-of-year attributable to the high experimental flow is likely not <br />discemable from other hypothesized, more consistent mortality factors associated with <br />the mainstream, including cold temperatures (Valdez and RyeI1995), predation, or loss <br />of habitat. <br /> <br />Non-native Fish Suppression Flows <br /> <br />The non-native fish suppression flows would be extended by one week into April under <br />the Proposed Action, These fluctuations could follow a November-December high flow <br />that would hypothetically rework sediment in sandbars and pools of eddies (Le" <br />backwaters) the latter serving as habitat for young fish. These habitats are most often <br />utilized by young fish emerging from tributaries in spring or summer, The time period <br />proposed does conflict slightly with the life history traits of humpback chub and other <br />native fish found in the Grand Canyon with respect to spawning, Fluctuations into the <br />first week of April might have an effect on larvae that might be dispersed into the <br />mainstream early as a result of tributary flows, Effects of fluctuations would be difficult <br />to segregate from other effects that contribute to larval mortality (temperature, <br />predation) under current mainstream conditions, The physical effects of the fluctuations <br />on the habitats may include either loss or accumulation of sediment in the pools as <br />sediment is transported downstream, <br /> <br />Mechanical Removal of Non-native Fish <br /> <br />Removal of non-native fish species in the Colorado River near the confluence of the <br />Little Colorado River began in January 2002 as an experiment to determine if reducing <br />predator load would benefit recruitment of HBC as well as other native fish that use the <br />Little Colorado River, Because a response in recruitment by native fish, including <br />endangered HBC, will not be likely to be recorded through monitoring until 2006 or <br />2007, the effect of mechanical removal on these target species presently is not known. <br />The methods used have, however, determined that salmonid and carp numbers can be <br />reduced with consistent and considerable effort (Coggins and Yard 2004), <br /> <br />Mechanical removal of non-native fish is accomplished by electrofishing and this <br />method of capture may have short-term negative effects on HBe. Hoop net monitoring <br />