8178

• UCREFRP Catalog Number: 8178
• Author: Anderson, R. and G. Stewart.
• Title: Riverine Fish Flow Investigations.
• USFW Year: 1999.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

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Table 8. Shannon Weaver Diversity, total number of species, number of
ephemeroptera, plecoptera and trichoptera taxa (E.P. T.), mean
density and density of shallow, middle and deep samples for the
Yampa.River, September 1998.

S.W. TOTAL MEAN Shallow Middle Deep
DATE INDEX SPECIES E.P.T. DENSITY n=2 n=2 n=2
Cross Mtn. Ranch
30 Jul. 1998 3.44 26 18 39.3 15 152 69
20 Aug. 1998 3.46 28 17 43.8 122 84 57
3 Sept 1998 3.54 38 24 197.0 419 442 321
8 Oct. 1998 3.64 27 17 48.7 25* 63* 199
Duffy Tunnel
23 Jul. 1998 3.93 33 21 82.2 184 215 91
20 Aug. 1998 3.69 39 21 316.2 429 935 532
3 Sept. 1998 3.63 41 23 314.0 412 975 495
8 Oct. 1998 3.56 35 22 345.8 56* 907 1112

*indicates sample collected in area of riffie dewatered prior to collection.

September is typically the month with the lowest base flow and the least amount
of available riffle habitat. Since invertebrate community characteristics were similar at
Duffy and Cross Mountain in September, the stations were combined for describing
community structure. Mayflies and caddisflies comprised 83 to 92% of the total number
of specimens in September (Table 9). Mayfly density and number of taxa decreased
with increasing depths. The highest caddisfly and total invertebrate density was at the
middle depth (0.4 to 0.6 ft). Density was 60% of the middle depth at both the shallow
(0.1 to 0.2 ft) and the deep samples (0.8 to 1.0 ft) (Table 9). The differences in density
between depths did not appeared to be due to velocity, since velocities were fairly
similar between the middle and deep sites (Table A2.I).

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