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50 of 51 fish), which was associated with the period immediately <br />following pikeminnow spawning in the Upper Colorado River. <br />5. Both non-listed native fishes and pikeminnow that passed through the <br />passageway and were released upstream of the diversion dam dispersed <br />upstream. Pikeminnow were found 30 miles upstream of the passageway <br />and other non-listed native fish (flannelmouth sucker and bluehead <br />sucker) were captured as far upstream as 57 miles. <br />6. Telemetry provided data on the fate of some pikeminnow that used the <br />passageway and were released upstream of the dam. Information <br />included the duration of their stay upstream of the diversion dam, <br />documentation of fallback over the dam, and subsequent movements <br />during the presumed pikeminnow spawning season. <br />Telemetered pikeminnow were generally larger than those that used the <br />fishway. However, telemetry did not provide data on pikeminnow use of <br />the passageway nor did it lead investigators to delineate aggregations <br />of pikeminnow during spawning or identify new and verify former <br />spawning areas in either the Gunnison or Upper Colorado rivers. <br />7. The decline of the number of Colorado pikeminnow and three other non- <br />listed native fishes found in the passageway fish trap during the 2- <br />1/2-month period between late-July and mid-October in 1999 and 2000 <br />were not correlated with river water volume or the mean daily <br />discharge. The high flows that occurred during this period apparently <br />were not correlated with the decline of three non-listed native fishes <br />moving through the passageway. <br />There was a trend apparent, however, from 1996 to 2000 during the <br />post-runoff months of July, August, September, and October: the <br />numbers of these three non-listed, native fish declined steadily. One <br />interpretation is that the decline of these three native fishes found <br />in the fish trap during this period was attributed to a slow, long- <br />term attrition or depletion of the numbers of native fish in <br />downstream river reaches as they moved through the passageway. In <br />other words, fish moved through the passageway faster than they moved <br />up to the dam from downstream areas. <br />8. The fish trap is a useful tool and serves as a 'point-source' location <br />for removal of problematic nonnative fish. It allows selective <br />enhancement of habitat use by native fishes from downstream areas. <br />48