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I I I I I I I I I I I I I I I I I I I In the main channel the vast majority of fish caught were over 15 cm, however in backwaters the majority of fish were less than 15 cm. Non-native cyprinids as a group were the most common fish sampled in backwater and most of them were deliberately not netted. The next most common species in bad.-waters were roundtail chub (17%), carp (15%), t1annelmouth sucker (10%) and white sucker (9%). Largemouth bass were about 6% and green sunfish were 5% of the total in the backwaters sampled. For fish over 15 cm the most common species were carp, t1annelmouth sucker and white sucker (Table 3). LENGTH FREOUENCY and MEAN LENGTH Length frequency histograms given in Appendix C Figures I, 2 and 3 are for total fish captured in \998 and \999. The length frequency histograms for bluehead sucker were very similar between years on the Yampa River. On the Yampa river the Duffy station in 1999 had 39% bluehead sucker at 40 cm or larger, in contrast to only 2% at the Sevens. The Colorado River had 21% of blue head sucker at and over 40 cm. Duffy also had the highest mean length in 1999 of blue head sucker at 382 mm, Sevens had the smallest mean length of 336 mm and it was 366 mm in the Colorado River (Table 4). Mean lengths between all sites were statistically different at P<O.OOI in 1999 for bluehead sucker. The length frequency histograms were also different for t1annelmouth sucker between the three sites. Duffy in 1999 had the highest percent (44%) offish over 50 cm, and Sevens the lowest at 16%, and it was 28% in the IS-Mile Reach in 1999 (Figure A). The Colorado River had the highest percent (28%) of fish under 40 cm and fish under 40 cm were only 6% for both sites on the Yampa (Appendix C Figures 4,5 and 6). Mean length offlannelmouth sucker in 1999 in the Colorado River was 422 mm and it was 465 and 486 mm for Sevens and Duffy, respectively (Table 4). The higher mean length on the Yampa River reach was a 33