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~ Table 3. Simpson's Index of Diversity for each sample station, based on all tnacroinvertebrate <br />taxa identified. <br />• Diversity <br />Stdt14II 1!'I3LGl1 October <br />D1 0.30 0.17 <br />D2 0.18 0.16 <br />D3 0.16 0.51 <br />D4 0.13 0.11 <br />DS 4.14 41Q <br />Mean 0.18 0.21 <br />U1 0.17 0.11 <br />U2 0.16 0.18 <br />U3 0.59 0.07 <br />U4 0.01 0.02 <br />U5 9~Z Q.bQ <br />Mean: 0.24 0.20 <br />Note: Simpson's Index of Diversity, b, is calculated as follows: x = F, p,?, where p; is the <br />proportion of the total number of individuals (all species) in species i. <br />Fish Populations: <br />Fish populations were not assessed by this study, however, we contacted Sherman Hebein, <br />Fisheries Biologist with the Colorado Division of Wildlife's Southwest Region headquartered <br />in Montrose. According to Hebein, the Division does not have a regulaz fish sampling <br />program in the North Fork River. The only data that he had from the North Fork in the <br />vicinity of this study was from a survey conducted in July, 1976, at a site approximately 1 <br />mile downstream of Somerset. The survey was conducted using electrofishing methods along a <br />500 ft reach of the river. Six species were recorded, including 1 brown trout, 10 bluehead <br />suckers, 17 white suckers, 5 flannelmouth suckers, 60 speckled dace, and 53 mottled sculpins. <br />The brown trout accounted for only 1 percent of the biomass captured. During the same <br />summer, two other sites farther downstream were surveyed, one a half mile upstream of the <br />confluence with the Gunnison River, and the other just below the Hotchkiss National Fish <br />Hatchery. The most productive of those two sites was the one neaz the hatchery, where they <br />captured 47 rainbow trout, 2 brown trout, 24 mottled sculpins, 3 white suckers, 2 <br />flannelmouth suckers, 8 bluehead suckers, and 1 roundtail chub. At the site near the <br />confluence, they captured 7 mottled sculpins, 26 speckled dace, and 1 roundtail chub. <br />According to a report from the Colorado Division of Wildlife by Woodling (1985), the North <br />Fork should also support populations of longnose dace, longnose sucker, and fathead <br />• 13 <br />