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

cooler in the 1992 to 1996 period compared to 2002 to 2006. This was due to relatively high and
cold flows observed in 1993 and 1995. Green River water temperatures in lower Lodore Canyon
and Mitten Park in the period 2002 to 2006 were similar except for a slightly elevated mid-July
maximum temperature in downstream Mitten Park, reflecting relatively little influence of the
warmer but relatively low Yampa River in those drought years (Fig. 14).
Thus, three actions subsequent to dam closure in 1962 have incrementally modified flows
and temperatures in the Green River upstream and downstream of the Yampa River to a state
that more closely resembles historical, unregulated conditions. The flow and thermal regimes
observed in 2002 to 2006 likely will reflect those that would be realized in low or moderately-
low flow years, under new Flaming Gorge Dam flow and temperature recommendations (Muth
et al. 2000), especially if Flaming Gorge Dam penstock releases are warmer such as in 2006.
Therefore, studies conducted in the five years from 2002 to 2006 (albeit, 2005 baseflows were
average) offered an opportunity to assess fish community response to flows that were at the
lower end of the recommendations spectrum. Amore complete assessment of fish community
response will be possible only with additional years of sampling conducted in average,
moderately-high, or high flow years.
During 2002 to 2006, warmer temperatures in Lodore Canyon resulted in minimal water
temperature differences between the Green River upstream of the Yampa River and the Yampa
River (Table 2), which was a goal of flow and temperature recommendations of Muth et al.
(2000). Minimizing temperature differences may reduce the likelihood of temperature shock
when Colorado pikeminnow larvae are carried from the warm Yampa River flows into the colder
Green River (Berry 1988, Tyus 1991). This problem may be more pronounced when Yampa
River flows are very low and warm and flows in the regulated Green River are higher and colder.
Composition of the fish community in Browns Park, Lodore Canyon, Whirlpool Canyon,
acid Island-Rainbow Park reaches, 2002-2004 and 2005-2006.A total of 209,466 specimens
representing 9 native and 19non-native species and 7 hybrid combinations- were captured by all
sampling gears during 2002 to 2004 (Table 3). An additional 68,466 specimens representing 11
19