9556

• UCREFRP Catalog Number: 9556
• Author: Bestgen, K. R., K. A. Zelasko and C. T. Wilcox.
• Title: Non-native fish removal in the Green River, Lodore and Whirlpool canyons, 2002-2006, and fish community response to altered flow and temperature regimes, and non-native fish expansion.
• USFW Year: 2007.
• USFW - Doc Type: 115,
• Copyright Material: NO

INTRODUCTION
Introduction and establishment ofnon-native fish in western rivers of the USA is a major
threat to conservation of native fish assemblages (Minckley and Deacon 1968, Stanford and
Ward 1986, Moyle et al. 1986, Carlson and Muth 1989, Minckley and Deacon 1991, Olden et al.
2006). In the upper Colorado River Basin, non-native fish invasions began over 100 years ago,
with introduction of channel catfish Ictalurus punctatus, common carp Cyprinus carpio, and
salmonids for sport fishery purposes. In the 1960's, small-bodied species such as red shiner were
relatively rare in the Green River sub-basin of the Upper Colorado River Basin (Vanicek et al.
1970), but by the 1970's were expanding rapidly (Holden and Stalnaker 1975a and 1975b). By
the 1980's, red shiner was a dominant species in low-velocity habitat used by early life stages of
native fishes, and potential negative effects of that species and other small-bodied fishes have
been documented (Haines and Tyus 1990; Dunsmoor 1993; Ruppert et al. 1993; Muth and
Snyder 1995; Bestgen et al. 1997; 2006). More recently, piscivores such as smallmouth bass
Micropterus dolomieu and northern pike Esox lucius have established and are common in the
lower Yampa River and the upper and middle Green River basins (Anderson 2002; 2005,
Bestgen et al. 2006, Finney 2006). The predatory threat of these large-bodied taxa is substantial
and control programs have been initiated to reduce their abundance and negative effects on
native fishes.
Altered flow, sediment, and temperature regimes in regulated rivers have also been
implicated as factors responsible for reduced distribution and abundance of native aquatic biota
in the Colorado River Basin (Petts 1984, Ward 1989, Ward and Stanford 1995, Stanford et al.
1996, Poff et al. 1997). In these snow-melt dominated streams, dams reduce spring discharge
maxima, which disrupts channel-flood plain interactions and channel forming processes. Deep-
releases from reservoirs reduce spring, summer, and autumn water temperature downstream from
dams and cause shifts in composition of fish and invertebrate communities from warm
stenothermic native species to non-indigenous cold-tolerant eurytherms (Holden 1979, Ward and
Stanford 1979, Stanford et al. 1996). Remnant populations of native fishes may persist as long-
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