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The EPT index was employed to assist in the analysis of the data. It is a direct measure of <br />taxa richness among species that are typically considered more sensitive to pollution or <br />other perturbations. This measurement is simply given as the total number of identified taxa <br />in the orders Ephemeroptera, Plecoptera and Trichoptera found at each station. The EPT <br />and richness metrics were used to measure numbers of taxa present at each location. The <br />difference between EPT and richness values is that the EPT only includes taxa from <br />Orders that are considered to be sensitive to disturbances, and richness includes all taxa. <br />Results obtained by these metrics provide a description of changes in community <br />complexity throughout the study area. These results are most valuable when compared <br />among sites within the same system. <br />Taxa richness was also reported for each sampling event during the study. This <br />measurement is reported as the total number of different taxa collected on each date from <br />each sampling location. It is similar to the EPT index, except that it includes all different <br />identifiable benthic macroinvertebrate species. It is useful for describing differences in <br />habitat complexity or aquatic conditions between rivers or site locations. Taxa richness and <br />EPT index values indicated similar trends among the sites on each sampling occasion <br />(Figure 39 and 40). Overall, major aquatic macroinvertebrate groups were well <br />represented at all sites in the study area. Values were generally lower immediately below <br />the reservoir and increased at sites downstream. A slight decline in these metric values <br />occurred at RFR-C. As expected, changes in the physical environment resulted in the <br />loss and replacement of certain taxa along a longitudinal gradient. <br />Biomass values provide information in terms of weight of macroinvertebrates produced by <br />habitat at each site. Density and biomass provide a means of measuring and comparing <br />productivity at each sampling location. Benthic macroinvertebrate density and biomass <br />were used as an indication of production at each site location. Although these <br />measurements are closely related they do not always indicate the same trends. The <br />density value is based on the mean number of individuals that were collected by <br />quantitative sampling, whereas biomass is a function of the number and weight of <br />individuals. <br />Draft Final Report, Fryingpan and Roaring Fork Rivers February 12, 2003 <br />Miller Ecological Consultants, Inc. Page 46