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7/14/2009 5:01:47 PM
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UCREFRP
UCREFRP Catalog Number
8234
Author
Marsh, P. C. and M. E. Douglas
Title
Predation by Introduced Fishes on Endangered Humpback Chub and Other Native Species in the Little Colorado River, Arizona
USFW Year
1997
USFW - Doc Type
Transactions of the American Fisheries Society
Copyright Material
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235 <br />Discussion <br />Effects on the native fish component <br />Holden (1979) considered riverine fishes to include <br />obligate and facultative riverine species. He further <br />divided obligate riverine species into species re- <br />quiring rivers for all their ecological needs and <br />those requiring rivers for a portion of their life his- <br />tory. The effect of damming a river on obligate riv- <br />erine species is generally negative and is a major <br />cause in the decline of these species (Holden 1979). <br />Observations made during this study, suggest the <br />most obligate riverine species, i.e. Colorado squaw- <br />fish, speckled dace and bluehead sucker, were most <br />affected by impoundment of the White River. <br />During our study, a single wild Colorado squaw- <br />fish was captured above the dam following its clo- <br />sure. This adult specimen, captured in 1985, was the <br />last wild Colorado squawfish verified in the White <br />River above Taylor Draw Dam. Adult Colorado <br />squawfish from the White River undertake exten- <br />sive potamodromous migrations for spawning in <br />the Green and Yampa rivers (Martinez', Tyus 1990). <br />Martinez' reported the migrations of one adult Col- <br />orado squawfish captured near Rangely, Colorado, <br />in 1983. This fish, recaptured near known spawning <br />sites in the Yampa River in 1984, was subsequently <br />caught by an angler in the White River near its orig- <br />inal capture site in 1985, thus confirming at least <br />700 km of upstream and downstream movements in <br />three rivers (Martinez) . The effect on Colorado <br />squawfish, formerly resident in the river above the <br />dam prior to impoundment, becomes obvious. Fur- <br />ther, stocking there does not seem a long-term solu- <br />tion to maintaining this species in its historic range <br />above Taylor Draw Dam (Trammell 1991, Trammell <br />et al. 1993). <br />The decline in relative abundance of both speck- <br />led dace and bluehead sucker following impound- <br />ment is probably attributable to their obligate river- <br />ine life histories. Speckled dace, a more lotic adapt- <br />ed species (Minckley 1973, Woodling,' Sublette et <br />al. 1990), and bluehead sucker, largely limited to <br />relatively swift-flowing waters over cobble or grav- <br />el (Baxter & Simon 1970, McAda & Wydoski 1983, <br />Sublette et al. 1990), displayed an affinity for flow- <br />ing habitats in the White River (Chart 1987). While <br />their reduced abundance in the reservoir could be <br />attributed to their lotic preferences, reductions of <br />these species below the dam in 1989-1990 was not as <br />readily explained. <br />Chart (1987) reported speckled dace reproduc- <br />tion to be especially high below the dam in 1985. He <br />suggested that habitat preference of adult speckled <br />dace should preclude competition with the burge- <br />oning fathead minnow population, but young <br />speckled dace would likely face considerable com- <br />petition from this species. Red shiner, the most <br />abundant species below the dam in 1989-1990, may <br />be a serious competitor with native species in the <br />Colorado River Basin (Holden 1979, Nesler7). The <br />combined effects of fathead minnow and red shiner <br />(Karp & Tyus 1990) may have contributed to the re- <br />duction of speckled dace. Because speckled dace <br />are short-lived (few live beyond 3 years, Sigler & <br />Sigler 1987), mortality of their young due to compe- <br />tition and lack of recruitment may explain their de- <br />mise below the dam. <br />Chart (1987) suggested bluehead suckers in the <br />lower reaches of the White River in Colorado came <br />from reproduction by this species in and above the <br />vicinity of Kenney Reservoir. This belief was sub- <br />stantiated by Lanigan & Berry (1981) who showed <br />bluehead suckers in the White River in Utah were <br />scarce, composing less than 0.5% of all fish collect- <br />ed. During our investigation, bluehead suckers <br />were most abundant above the dam axis from 1983 <br />to 1985. Chart (1987) attributed the reduction in <br />young-of-year bluehead suckers below the dam in <br />1985 to poor drift of larvae through the reservoir. <br />He further reasoned that this loss of supplemental <br />recruits from upstream spawning areas would result <br />in the long-term decline of bluehead suckers below <br />the dam. This mechanism explained the stark re- <br />ductions of this species below the dam in 1989-1990. <br />e Woodling, J.1985. Colorado's little fish: a guide to the minnows <br />and other lesser known fishes in the state of Colorado. Colorado <br />Division of Wildlife, Denver: 77 pp. <br />Nesler, T.P 1991. Endangered fishes investigations. Job Pro- <br />gress Report. Federal Aid in Fish and Wildlife Restoration Pro- <br />ject SE-3. Colorado Division of Wildlife. Fort Collins. 69 pp.
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