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<br />EXECUTIVE SUMMARY <br /> <br />The purpose of thi s 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 /> <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 ictalutids 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 /> <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 />mil e reach that had been implanted wi th LOTEK@ coded transmi tters. Ground <br />surveillance was used to monitor fish movements with a boat and by a land-based <br />tracking station and data logger, located at the diversion dam, that constantly <br />monitored and recorded signals from transmitter-tagged fish immediately <br />downstream and immediately upstream of the diversion dam. <br /> <br />The following conclusions from this research were: 1) no transmitter-tagged <br />sub-adult or adult Colorado pikeminnow were documented using the newly- <br />constructed notch to pass by the GVIC Diversion Dam; 2) ten adult Colorado <br />pikeminnow were captured upstream of the diversion dam, It is unknown whether <br />these 10 fish had used the notch at the diversion dam or simply passed over the <br />diversion structure when it was inundated during high water in 1998 or during <br />prior years; 3) 2,505 fish were captured upstream of the diversion dam prior to <br />spring runoff (27 April) and during post,runoff (17 July to 21 October). Of the <br />1.815 native and nonnative fish that were marked downstream of the GVIC Diversion <br />Dam, only one adult carp was recaptured upstream of the diversion dam. This fish <br />was assumed to have used the drop structure and notch to pass by the diversion <br />dam because there was no water spilling over the diversion dam during the one- <br />week period between marking and recapture; and 4) forty,six fish were recaptured <br />downstream of the GVIC Diversion Dam--forty were native fish and six nonnative <br />fish. Recapture rate was 2.5% of all fish marked. <br /> <br />viii <br />