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<br />1993). Direct evidence or predation includes native fishes obtained <br />from stomach contents of nonnative fishes and by Yisual observation of <br />predation. The loss of early-life history stages of the razorback <br />sucker has been linked to predation by nonnatiye fishes. While it is <br />not likely that nonnative fishes that have become established in the <br />Upper Colorado River Basin can be eliminated, preventive measures and <br />active control programs could be implemented to reduce the abundance of <br />nonnative fishes in riverine and adjacent floodplain habitats. <br />Consequently, then, reducing the abundance of nonnative fishes would <br />reduce the potential for predation and competition on endangered <br />fishes. Removal and disposal of all nonnative game fishes will be <br />coordinated with representatives from the Colorado Division of <br />Wildlife. <br /> <br />Efforts to capture fish will be staggered and no more than one-third of <br />the native fishes will be captured and marked prior to runoff, during <br />late-March through mid-April; the other two-thirds will be captured and <br />marked after runoff, during July. The reason for this is that fish <br />captured and marked prior to runoff could be swept far downstream <br />outside the target study area and could take some time before migrating <br />upstream to the diversion dam or may never return. Also, key criteria <br />identifies that the passage structure at GVIC should be designed to <br />pass fish upstream particularly during low flows, which routinely occur <br />during July, August, and September. Therefore, it is important to <br />capture and mark a majority of the fish downstream of the diyersion <br />structure during summer low-flow conditions and determine if they will <br />use the passage structure and move upstream past GVIC during this time. <br /> <br />Therefore, the first year of the evaluation will concentrate on <br />capturing and marking fish downstream of the GVIC Diversion Dam and <br />sampling upstream of the dam to recapture tagged fish. During the <br />first year, all sub-adult and adult fish that will be marked will be <br />captured within 2 river miles downstream of the diversion structure. <br />After evaluating results of the number of fish recaptured up- and <br />downstream of the diversion structure during the first year, some fish <br />may be captured and marked upstream of the diyersion structure during <br />the second year to determine if fish can move downstream past the <br />diversion structure. <br /> <br />Sampling to recapture tagged fish will be conducted biweekly following <br />initial marking, up-, downstream, and in the immediate vicinity of GVIC <br />diversion dam. Upstream sampling to recapture fish will be between the <br />GVIC Diyersion Dam and Price-Stubb Dam; downstream sampling will be <br />conducted from GVIC to 32 Road (riyer mile 176.4). Every effort will <br />be made to recapture as many fish as possible with electrofishing to <br />determine if marked fish had passed up- or downstream of the GVIC <br />Diversion Dam. More effort will be placed sampling upstream of the <br />diversion dam attempting to recapture tagged fish that had moved from <br />the downstream reach. During low-flow periods during July, August, and <br />September, a Smith-Root@, barge-electrofishing unit would be used to <br />sample immediately below the GVIC Diversion Dam in an attempt to <br />recapture marked fish, Larger electrofishing boats cannot negotiate <br />the shallow-water areas immediately downstream of the diversion dam <br />during low flows. <br /> <br />5 <br />