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<br />, <br /> <br />19 <br /> <br />Kaeding and OSlllndson {I98n noted that the majority of adult Colorado sQuawfish <br />were captured in gravel pit ponds which are only accessible during the high-flow <br />period. These findings are consistent with spring Colorado sQuawfiSh captures <br />throughout the Green and Colorado River basins (Archer et al. 1986). Colorado <br />sQuawfish appear to seek. out flooded backwater-type habitats in the spring <br />because of their wanner temperature and abundant food sources. Ut il izat ion of <br />these types of habitat is bel ieved to be very important to preparing adult <br />Colorado sQUaWfish for spawning which generally occurs from mid-July through <br />August. While no specific data are available, the Service is concerned that the <br />Qua 1 ity and ivailabil ity of flooded backwater habitats may be further dimini shed <br />as a result of the Muddy Creek. project. <br /> <br />With the decline of high spring flows, Colorado River endangered fishes initiate <br />spawning. Spawning and recruitment appear to be the 1 i fe stages most 1 imiting <br />the survival and recovery of Colorado sQuawfish in the Colorado River. In a <br />recent study of relations between maximum annual river diSCharge and relative <br />abundance of age-Q Colorado sQuawfish, McAda and Kaeding (1989) found that the <br />abundance of age-Q Colorado sQuawfish is correlated with the magnitude of peak. <br />spring flows in the Colorado River. Their analysis suggests a maximum annual <br />streamflow of 30,00II-40,000 cfs (as measured at the Colorado-Utah border) could <br />resul t in increased reprOductive success. The MUddy Creek. project wi 11 reduce <br />the probability of achieving these peak. streamflows. <br /> <br />Humpback. cOOb spawn during or immediately after high spring flow. Spawning is <br />apparently the tinewben separation between humpback chub and roundtail chub <br />(Gilg robust~ has bnXen down in many areas; this could be due to reduced <br />spring flows IlISDI, Bureau of land Management 1989>' This is of greatest <br />concern in Black Rocks and Westwater Canyon, where cumulative depletions of the <br />Muddy Creek project, and other recent or planned development would cause 10 to <br />13 percent "'tion in monthly and instantaneous flow (USDI, Bureau of land <br />Management 1919). <br /> <br />Another consi4eratiOll relative to peak. spring flows during May and June pertains <br />to the effect these flows have on maintaining a suitable cobble substrate for <br />spawning. De Service believes fine sediments may be deposited on cobble areas <br />within the l~le reach that require periodic flushing to provide suitable <br />spawning conditions. Although no specific sediment data is available, the <br />changes in peIk fl~ ckIe to the Muddy Creek project are not expected to <br />appreciably affect the capability of peak flows to flush fine sediment from <br />cobble substrite. <br /> <br />The Service evaluation on the potential impacts of the Muddy Creek project <br />channel mailltlllilllCe was based primarily on analysis conducted by Simons et al. <br />(1983). The7 C1IIlClllded that the upper Colorado River transports a sediment load <br />far below its sedi..t-carrying capacity. As a result, reductions in flows do <br />not result iuggradation in the IS-mile reach. In addition, due to the armored <br />nature of Its dlamel. no degradation is lik.ely to occur within potential <br />discharge rilll!l!S. Due to these conditions, the Service concludes that the Muddy <br />Creek. project Ifill not significantly affect the current channel morphology. <br />