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Table 2. Stream taxa identified in macroinvertebrate samples collected in the North Fork of the <br />Gunnison River east of Somerset, Colorado. <br />• <br />('race Order <br />Acarina Hydrocazina <br />(Water mites) <br />Insecta Coeoptera <br />(Beetles) <br />Diptera <br />(True flies) <br />Ephemeroptera <br />(Mayflies) <br />• <br />Plecoptera <br />(Stoneflies) <br />Genus <br />Elmidae (Diving beetles) <br />Chironomidae (Midges) <br />Empididae (Dance flits) <br />Baetidae Baetis <br />Ephemerellidae Drunella grandis <br />Serratella <br />Heptageniidae <br />Leptophlebiidae Paraleptophlebia <br />Perlidae Claassenia sabulosa <br />Perlodidae Isoperla <br />Pteronazcyidae Pteronarcella <br />Trichoptera <br />(Caddisflies) <br />Brachycentridae Brachycentrtu <br />Hydropsychidae Hydropsyche <br />Lepidostomatidae Lepidostoma <br />Leptoceridae Oecetis <br />Counts of macroinvertebrates in the individual replicate samples ranged from 76 at station U2 <br />in October to 663 at station D1 in Mazch. Abundance estimates of the four major <br />macroinvertebrate orders (Ephemeroptera, Plecoptera, Trichoptera, and Diptera) at the sample <br />stations ranged from 327/m2 (station U2) to 1617/m2 (Station U4). These four orders typically <br />accounted for over 80 percent of the total tnacroinvertebrate population. The most common <br />organisms were Brachyceturus caddisfly larvae, Serratella mayfly nymphs, and chironomid <br />larvae. In la[e summer, rocks at the edge of the channel were covered with thousands of <br />Brachycentrus cases. Particulazly conspicuous in the samples were the relatively lazge <br />predaceous nymphs of the stonefly Claassenia sabulosa, which often approached 3 cm in <br />length. Appendix 2 contains all of the count data from the samples that were collected in <br />Mazch and October. <br />9 <br />