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Filters: partyWithName: Bestgen, Kevin R (X) > Extensions: Citation (X) > Types: Journal Citation (X)

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ABSTRACT-In the Gila River drainage of southwestern New Mexico, roundtail chub (Gila robusta) were historically widespread and relatively common in mainstream and larger tributary habitats. Natural and human-induced habitat alterations and establishment of non-native predator fishes are believed to be the primary reasons for the current reduced range and abundance of this species. Roundtail chub has been extirpated from the San Francisco River, a major tributary of the Gila River. It persists mainly in reaches of the Gila River drainage that are free of non-native predators or where natural flow regimes and periodic flooding might act to suppress introduced predator populations and maintain habitat variability....
The Iowa darter (Etheostoma exile) was first captured in Little Yampa Canyon, Yampa River, Colorado, by electrofishing in autumn 2003, and abundance of this nonnative species increased during 2004?2007. The Iowa darter also expanded downstream 229 river km, based on captures of young fish in a drift net at the confluence of the Yampa and Green rivers in 2005, and in light traps in the Green River near Jensen, Utah, in 2005?2007. Likely introduction of the Iowa darter via bait-bucket transfer suggests that additional legal deterrents might be needed to reduce further illicit introductions of potentially problematic nonnative fishes in the Colorado River Basin. Published in The Southwestern Naturalist, volume 53,...
Predation experiments, field studies, and individual-based-model (IBM) simulations revealed factors that affected the survival and recruitment of early life stages of endangered Colorado pikeminnow Ptychocheilus lucius in the Green River basin, Utah and Colorado. Small-bodied, nonnative red shiners Cyprinella lutrensis attacked Colorado pikeminnow larvae an average of once per minute, and predation success approached 30% in laboratory aquaria. Attack rate was also high in mesocosm experiments; turbidity and alternative prey reduced predation success. Distributions of hatching dates derived from otolith daily increment analysis showed that large cohorts of Colorado pikeminnow larvae that hatched in the Green River...
Historically widespread and abundant throughout warm water reaches of the Colorado River basin, the endemic razorback sucker (Xyrauchen texanus) is now rare and listed as endangered (United States Fish and Wildlife Service, 1991). Mainstem dams that alter habitat and introduction of non-native fishes which prey upon or compete with early life stages are among the large-scale ecological disturbances that have negatively affected the razorback sucker (Tyus, 1987; Minckley et al., 1991). Rarity of larval and especially juvenile razorback suckers in collections, and presence of only aged adults in remaining populations indicates recruitment failure (McCarthy and Minkley, 1987; Lanigan and Tyus, 1989; Minckley et al.,...
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The endangered bonytail Gila elegans, a large-bodied, main-stem cyprinid endemic to the Colorado River Basin of the American Southwest, was once widespread and abundant in warm-water-stream reaches. Negative effects of altered flow and temperature regimes downstream of dams, other habitat changes, and establishment of nonnative fishes have reduced populations of native fish throughout the basin, and wild bonytails may be extirpated. Hatchery reared bonytails are stocked in formerly occupied habitat to rebuild depleted populations, but their ecology is poorly understood. In 2002?2007, sampling in the middle Green River from upstream and downstream of stocking locations in Dinosaur National Monument documented survival...
Colorado squawfish (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus) were formerly widespread and abundant in large streams and rivers throughout the Colorado River Basin (Miller, 1961; Minckley, 1973; Holden and Wick, 1982). Self-sustaining populations of Colorado squawfish are extant in the Upper Colorado River Basin (Holden and Wick, 1982) and are federally listed as endangered (United States Department of Interior, 1974). Razorback sucker, proposed for federal listing as an endangered species (United States Department of Interior, 1990), occurs sporadically in the Upper Colorado River Basin (Tyus, 1987; Lanigan and Tyus, 1989) and in some mainstream Colorado River reservoirs in the Lower Colorado...
Capture?recapture sampling of 819 km of streams in the Green River subbasin, Utah and Colorado, of the Colorado River basin was conducted in 2000?2003 to estimate population demographic parameters and recovery status for endangered Colorado pikeminnow Ptychocheilus lucius. Parameter estimates from a Huggins robust-design, multistratum model suggested a basinwide decline in the abundance of adult (total length, ?450 mm) Colorado pikeminnow. Reductions were most severe in the middle Green River (59%) and White River (63%), the two largest population segments. Reductions were less severe in the Yampa River (29%), Desolation?Gray Canyon (11%), and lower Green River reaches (36%). In 2001, the first year the entire subbasin...
Understanding the mechanisms by which nonnative species successfully in vade new regions and the consequences for native fauna is a pressing ecological issue, and one for which niche theory can play an important role. In this paper, we quantify a com prehensive suite of morphological, behavioral, physiological, trophic, and life-history traits for the entire fish species pool in the Colorado River Basin to explore a number of hypotheses regarding linkages between human-induced environmental change, the creation and mod ification of ecological niche opportunities, and subsequent invasion and extirpation of species over the past 150 years. Specifically, we use the fish life-history model of K. O. Winemiller and K....
Growth and survival of Colorado squawfish, Ptychocheilus lucius, larvae under fluctuating 18, 22, and 26 degrees C (5 degrees C diel fluctuations) and constant 18, 22, 26 degrees C, and 30 degrees C temperature conditions and ration size corresponding to 12.5, 28, 64,142, 320 brine shrimp nauplii fish(-1) day(-1) was determined from laboratory experiments. Growth was optimal at 31 degrees C and high at temperatures of 26 degrees C to 30 degrees C, at the highest food abundance. Lowest growth was under lowest food rations and highest temperatures. Growth of Colorado squawfish larvae declined substantially at temperatures < 22 degrees C. Neither growth nor survival was significantly different between fluctuating or...
We used tag?recapture data to estimate apparent survival and capture probability for 119,129 hatchery-reared, federally endangered razorback suckers Xyrauchen texanus stocked into upper Colorado River basin streams during 1995?2005. Effects investigated included reach, year, and season of stocking; fish total length (TL) at time of stocking; survival in the first year after stocking versus in subsequent years; and sampling effort. Recapture data were also used to describe poststocking movement. First-year survival rate for stocked razorback suckers of average TL (252.5 mm) was low: 0.05 (95% confidence interval [CI], 0.042?0.071). Total length at stocking and first-year survival were positively correlated; survival...
    map background search result map search result map Survival, Condition, Habitat Use, and Predation on Stocked Bonytails (Gila elegans) in the Green River, Colorado and Utah Survival, Condition, Habitat Use, and Predation on Stocked Bonytails (Gila elegans) in the Green River, Colorado and Utah