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Whirlpool Canyon reaches 1 and 2, respectively, and two were from Island-Rainbow Park. Capture rates by electrofishing were 0.39 fish/h for reaches LD1 through LD4. The length- weight relationship calculated for large juvenile and adult Colorado pikeminnow captured in the Green River, Lodore Canyon, 1994 to 1996 was: Weight(g) = 39.04 *eo.0065*rc ( ), r' = 0.98. The length-weight relationship calculated for large juvenile and adult Colorado pikeminnow captured in the Green River, Lodore Canyon, 2002 to 2004 was: Weight (g) = 64.09 *eo-"" *' c->, r' = 0.94. Length-weight relationships showed Colorado pikeminnow from Lodore Canyon were, on average, heavier at length in the 1994 to 1996 period than fish from the 2002 to 2004 period (Fig. 44). The shape of the curve for the 1994 to 1996 period was not affected by the largest fish. We detected PIT tags in 22 of the 41 Colorado pikeminnow we captured compared to only 2 out of 17 in the 1994 to 1996 period. Three of the four individuals captured and recaptured during this study were at large sufficiently long (captured in different sampling trips, one fish was captured in the same trip) to observe changes in length or weight. The three fish were at large about an average of 2 months of the summer growing season and despite negligible changes in TL, gained 4, 12, and 46% in weight. Young Colorado pikeminnow were captured in seine samples from the upstream Whirlpool Canyon reach in Echo Park (N = 5, 28 to 50 mm TL) and in the lower end of the Island-Rainbow Park reach (N = 15, 33 to 89 mm TL). Twelve of the 20 young pikeminnow were collected in 2002. Seven of these 12 were collected in spring 2002, which means they were produced in 2001. One young Colorado pikeminnow was collected in 2003 and seven were captured in 2004. 50