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<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 /> <br />Table 8. Shannon Weaver Diversity, total number of species, number of <br />ephemeroptera, plecoptera and trichoptera taxa (E.P,T.), mean <br />density and density of shallow, middle and deep samples for the <br />Yampa,River, September 1998. <br /> <br /> SW. I TOTAL I MEAN I Shallow Middle Deep <br />DATE INDEX I SPECIES I E.P.T. DENSITY n=2 n-2 n-2 <br /> Cross Mtn Ranch <br />30 Jut 1998 3.44 26 18 39.3 15 152 69 <br />20 Aug. 1998 3.46 28 17 43.8 122 84 57 <br />3 Sept. 1998 3.54 38 24 197.0 419 442 321 <br />8 Oct. 1998 3.64 27 17 48.7 25. 63. 199 <br /> Duffy Tunnel <br />23 Jut 1998 3.93 33 21 82.2 184 215 91 <br />20 Aug. 1998 3.69 39 21 316.2 429 935 532 <br />3 Sept. 1998 3.63 41 23 314.0 412 975 495 <br />8 Oct. 1998 3.56 35 22 345.8 56. 907 IIl2 <br /> <br />.mdicates sample collected in area of riffle dewatered pnor to collection. <br /> <br />September is typically the month with the lowest base flow and the least amount <br />of available rime habitat. Since invertebrate community characteristics were similar at <br />Duffy and Cross Mountain in September, the stations were combined for describing <br />community structure. Mayflies and caddisflies comprised 83 to 92% of the total number <br />of specimens in September (Table 9). Mayfly density and number of taxa decreased <br />with increasing depths. The highest caddisfly and total invertebrate density was at the <br />middle depth (0.4 to 0.6 ft). Density was 60% of the middle depth at both the shallow <br />(0.1 to 0.2 ft) and the deep samples (0.8 to 1.0 ft) (Table 9). The differences in density <br />between depths did not appeared to be due to velocity, since velocities were fairly <br />similar between the middle and deep sites (Table A2.I). <br /> <br />15 <br />