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I I I I I I I I I I I I I I I I I I I In 2000 the base flows were much lower than in 1998 and] 999 with flows between 30 and 80 cfs on the Yampa for most of the summer. At these flows, runs and rimes become rare at Duffy and most of the river is shallow, composed of wetted and shoal pools (Figure A51). At Duffy only 4% of the habitat is rime at 200 cfs and 57% is rimes at Com Lake at 1400 cfs (Table ]0). Total rime density is 12.5 time greater at Com Lake than Duffy. Duffy and Com Lake have roughly an equivalent amount of shallow rime (0.9%), but Duffy has no . very deep riffle habitat compared to 21% at Com Lake (Table A6). The habitat type most likely associated with adult bluehead sucker is the deep riffle and at Duffy there is only 0.001 halkm. Bluehead density in the Surveyed Site is 0.26 fish per 1000 m2. At Com Lake deep riffle is very common at 1.43 halkm (Table A6) and bluehead density is 21.5 fish per 1000 m2. Table 10. Habitat composition in arealkm and percent for major habitat categories at Duffy and Com Lake based on 2-D flow modeling. CORN LAKE DUFFY CORN LAKE DUFFY 1400 cfs 200 cfs 1400 cfs 200 cfs Habitat Ha/km Halkm Percent Percent Pool 0.393 2.14 6.8% 38.1% Run 1.93 3.24 30.8% 57.6% Riffle 2.98 0.239 56.6% 4.3% Rapid 0.213 0.001 5.8% 0.0% total area 5.52 5.62 Riffles are also the primary habitat for most aquatic macro invertebrates and the very low amount of rime habitat on the Yampa River suggests a much lower potential for macro invertebrate production compared to the Colorado River. Since invertebrate abundance may be limited by habitat abundance, this suggests that their availability as fish forage could be greatly different between the two sites. The very low fish densities observed at Duffy could be an effect of reduced forage potential there. This concept should become clearer after habitat data is available for Sevens and Lily Park. 43