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EXECUTIVE SUMMARY <br />The purpose of this study was to evaluate whether sub-adult and adult <br />Colorado pikeminnow and other native fishes would move upstream through a series <br />of newly-constructed alternating pools and riffles and a notch in the Grand <br />Valley Irrigation Company (GVIC) Diversion Dam on the Upper Colorado River near <br />Palisade, Colorado. Study direction was modified in August 1998 that resulted <br />in altering tagging techniques for the remainder of 1998 and canceling field <br />sampling for most of 1999. Consequently, most of the stated study objectives <br />were not sufficiently addressed. <br />Methodology for this evaluation relied on two separate techniques, 1) mark <br />and recapture using electrofishing, and 2) telemetry, both applied independently <br />to determine if sub-adult and adult fish would use the passageway to pass by the <br />GVIC Diversion Dam. Sub-adult and adult fish of the most common large-sized, <br />native fishes (flannelmouth sucker, bluehead sucker, and roundtail chub) were <br />inserted with a PIT tag; other common sub-adult and adult nonnative fishes such <br />as common carp and white sucker were marked with an external, individual, <br />serially-numbered Floy° tag. Rainbow trout, brown trout, and sucker hybrids were <br />all marked by clipping the left pelvic fin. Only fish captured downstream of <br />the GVIC Diversion were marked or tagged. Centrarchids and ictalurids captured <br />up- and downstream of the GVIC Diversion Dam as "by-catch" were removed and <br />disposed. Sampling to recapture fish upstream of the diversion dam was conducted <br />once prior to- and 10 times following runoff. Eight days each were dedicated to <br />sampling downstream of the diversion dam to recapture fish prior to- and <br />following runoff. <br />The second method incorporated a digitally encoded telemetry system to <br />follow movements of sub-adult and adult Colorado pikeminnow captured in the 15- <br />mile reach that had been implanted with LOTEK~-coded transmitters. Ground <br />surveillance was used to monitor fish movements from a boat and by a fixed, land- <br />based tracking station and data logger, located at the diversion dam, that <br />constantly monitored and recorded signals automatically from transmitter-tagged <br />fish immediately downstream and immediately upstream of the diversion dam. <br />Summary results from this research were: 1) no transmitter-tagged sub-adult <br />or adult Colorado pikeminnow were documented using the newly-constructed notch <br />to pass by the GVIC Diversion Dam; 2) ten adult Colorado pikeminnow were captured <br />upstream of the diversion dam. It is unknown whether these 10 fish had used the <br />notch at the diversion dam or simply passed over the diversion structure when it <br />was inundated during high water in 1998 or during prior years; 3) 2,505 fish were <br />captured upstream of the diversion dam prior to spring runoff (27 April) and <br />during post-runoff (17 July to 21 October). Of the 1,815 native and nonnative <br />fish that were marked downstream of the GVIC Diversion Dam, only one adult carp <br />was recaptured upstream of the diversion dam. This fish was assumed to have used <br />the drop structure and notch to pass by the diversion dam because there was no <br />water spilling over the diversion dam during the one-week period between marking <br />and recapture; and 4) forty-six fish were recaptured downstream of the GVIC <br />Diversion Dam--forty were native fish and six nonnative fish. Recapture rate was <br />2.5% of all fish marked. <br />viii <br />