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<br />Table 19, Mean lengths of all species at the 15-Mile Reach, Colorado River 2000 to 2003, <br /> <br />Colorado River Mean length for all fish collect in cm <br />15-Mile Reach A B C <br />Species 2000 2001 2003 <br />Flannelmouth sucker 38,7 39,6 41,2 <br />Bluehead sucker 32,5 34,2 33.4 <br />Colorado pikeminnow 59.4 63,7 <br />Roundtail chub 24.4 21,8 27,7 <br />White S. + hybrids 26,1 <br />Channel catfish 40.2 41,9 42.4 <br />Carp 42,0 34,5 40,9 <br />Smallmouth bass 12,7 <br />Northern pike <br /> <br />It was rare in the baseline years to capture Age-O roundtail chub, but yearlings (11 to <br />20 cm) were the largest mode (size-group) by far in both 2000 and 2001. Age.1 roundtail <br />chub were rare in 2003 (Figures A I -16 & - I 7), which is an indication their YOY survival <br />was poorer in 2002 than earlier years, Fewer Age-1 chub in the population explains the <br />larger mean size of this species in 2003. <br /> <br />Carp had the highest variation in length distribution over the three years, In 2000 few <br />carp less than 35 cm were observed, but in 2001 there was a large mode from 11 to 20 cm <br />and a gap from 2\ and 35 em. In 2003, there was a large mode of carp between 13 and 35 <br />cm, indicating survival of Age-I carp in 2002 was good (Figures AI-41 & -42), <br /> <br />In both 2000 and 2001, the majority of white sucker were small, less than 20 cm. <br />This was reversed in 2003 when there were much fewer Age-O and Age-I sized fish (Figures <br />A 1-21 & 22). This suggested white sucker spawning success or survival of YOY fish was <br />less in 2002 and 2003 than in the two prior years. Nursery habitat for young fish should have <br />been increased in 2002 with the low flows. However, low flow years were found to have <br />increased abundance of centrarchid predators in the Yampa River, The large increase in <br />smallmouth bass numbers in 2003 suggested predation accounted for reduced Agc-O and <br />Age-I white sucker in the 2003 sample, <br /> <br />The minimum size channel catfish in the population was about 25 cm in both 2000 <br />and 2001. suggesting that channel catfish migrated to this area after they were already 25 to <br />30 cm. The collection of 14- and 16- cm channel catfish in 2003 indicated the spawning <br />conditions (temperature) were improved by the 2002 flows compared to other years, <br /> <br />Variation in the length frequency between years was not observed for largemouth <br />bass suggesting this species reproductivity did equally well in 2003 compared to earlier years <br />(Figures A I -48 & -49), In contrast Age-O small mouth bass numbers were much higher in <br />2003 (Figures AI-53 & -54) than in any of the prior surveys, <br /> <br />30 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />