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233 <br />N <br />W <br />performed using boat-mounted equipment at night <br />near shore along the reservoir's length. Gill nets <br />were set overnight in all major habitats (shallow <br />and deep coves, cliff and sloping areas, surface, bot- <br />tom and midlake). Seining accounted for 85-99% <br />of fishes collected (Martinez'`, Trammell 1991). Typ- <br />ically, larger fish, and all Colorado squawfish, were <br />identified and released. Large samples of small fish <br />were preserved in 10% formalin and returned to the <br />laboratory for identification and enumeration. <br />Results <br />Pre-impoundment species composition <br />Fish samples taken in 1983-1984 prior to closure of <br />Taylor Draw dam were dominated by four native <br />species; roundtail club Gila robusta, speckled dace <br />Rhinichthys osculus, bluehead sucker Catostomus <br />discobolus and flannelmouth sucker Catostomus <br />lattipinnis (Tables 1, 2). Three other native species <br />reported in pre-impoundment collections, Colora- <br />do squawfish, mountain whitefish Prosopium wil- <br />liamsoni and mottled sculpin Cottus bairdi, com- <br />prised no more than 0.5% in 1983 or 1984.OVeran, <br />native species accounted'for over 97% of the fish <br />wOeeted in 1983 (Fig. 2). In 1984, dominance by na- <br />tive species persisted, but not as overwhelmingly as <br />observed in 1983. Species composition above the <br />dam construction site in 1983 was about 88% native <br />and 12% non-native while below the dam axis <br />70.4% of the fish collected were native and 29.6% <br />were non-native. <br />Among introduced species, fathead minnows Pi- <br />mephales promelas were rarely collected in 1983, <br />but after 1984, fathead minnow numbers increased <br />dramatically in samples both above and below the <br />dam axis (Tables 1, 2). The greater proportion of <br />this species below the dam axis may have been due <br />to ponding in the vicinity of the dam construction <br />area that probably enhanced fathead minnow re- <br />production. Additionally, other non-native species <br />were collected including red shiner Cyprinella lu- <br />trensis, common carp Cyprinus carpio, black bull- <br />head Ameiurus melas and channel catfish ktalurus <br />punctatus, none exceeding 1.5%. A single, 200 mm <br />black crappie Pomoxis nigromaculatus was sam- <br />pled below the dam in 1984 (Table 1). These data <br />further substantiated preimpoundment dominance <br />by native fishes within the study area (Fig. 2). <br />Post-impoundment fish community changes <br />The White River fish community began showing in- <br />creased abundance of non-native species in 1984, <br />during construction of the dam: however, marked <br />changes occurred primarily in the reservoir in 1985, <br />the first year of impoundment. Fathead minnows <br />increased from 10.3% in the pre-impoundment res- <br />ervoir basin in 1984 to 60.2% of all fishes collected <br />in the reservoir in 1985 (Table 2). In this initial year <br />of impoundment, relative abundance of other non- <br />native species remained low. The most marked de- <br />crease among native species in the reservoir was ob- <br />served for speckled dace. Comprising about 20% to <br />30% of the fish collected throughout the study area <br />before impoundment. speckled dace accounted for <br />only 1.8% of the fish collected in the reservoir in <br />1985. <br />Subsequent fish collections made in the reservoir <br />in 1987 consisted of 61.2% non-native species (Fig. <br />2). Although fathead minnow numbers dominated <br />samples, and undoubtedly the reservoir's fish pop- <br />ulation, their relative abundance was offset by in- <br />creased collection of stocked rainbow trout Oncor- <br />hynchus mykiss (Table 2). Originally stocked as the <br />reservoir began to fill in 1984. rainbow trout have <br />been stocked annually to provide a sport fishery in <br />Kenney Reservoir. The apparent increase in rela- <br />tive abundance of roundtail club, flannelmouth <br />sucker, and common carp in 1987 seemed due to <br />their susceptibility to gill nets set in shallower <br />depths. Bluehead sucker abundance, however, was <br />much lower in the reservoir in 1987 than in 1985. <br />Numbers of speckled dace collected in 1987 contin- <br />ued to be conspicuously low. <br />Fathead minnows also dominated reservoir fish <br />collections (46,4%) in 1988 (Table 2). Black bull- <br />heads increased from 1.3% in 1985 to'17.2% (over <br />99% young-of-year) in 1988. The presence of adult- <br />sized green sunfish Lepomis cyanellus, bluegill Lep- <br />omis machrochirus. largemouth bass Micropterus