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

several non-native species and when summer flow levels were relatively higher and cooler. We
then compare trends in native fish abundance over the same time periods. We attempt to sort out
the relative effects of expanding populations of non-native fishes on native ones as well as
changes in flow and temperature regimes between the periods 1994-1996 and 2002-2006,
particularly in 2005 and 2006 when non-native fish removals were increased (Christopherson et
al. 2005, this study). We also discuss means, in part, to understand the overlapping and
potentially confounding effects of simultaneous fish removal and flow and thermal regimes on
non-native and native fishes.
The reach of the Green River, Utah and Colorado, downstream of Flaming Gorge Dam
offers an opportunity to evaluate effectiveness of actions to re-establish native fishes. This is an
ideal study area because more natural hydrologic and temperature regimes designed to benefit
native fishes have been implemented over a series of years. The Green River also has a source
pool of native fishes downstream, including the mostly unregulated and tributary Yampa River
and regulation-attenuated downstream reaches of the Green River, to re-colonize upstream
reaches. Furthermore, descriptions of the fish community are available from immediate pre-dam
(pre-1962) and post-dam (1964-1966) periods, as well as before and after installation of a
temperature control device (1978-1980). Additional sampling was conducted from 1994 to 1996
and in 2002-2004 that further evaluated changes in the fish community following
implementation of flow and temperature recommendations contained in biological opinions on
operation of Flaming Gorge Dam (U. S. Fish and Wildlife Service 1992, Bestgen and Crist 2000,
Muth et al. 2000, Bestgen et a1. 2006).
The newest set of flow and temperature recommendations for the Green River was
developed (Muth et al. 2000) and those recommendations were officially implemented in 2006
(Record of Decision, U. S. Bureau of Reclamation, 2006). Annual peak and base flow
recommendations were developed for each of five hydrologic conditions that ranged from dry to
wet, based on exceedance probabilities: dry (90 to 100% exceedance), moderately dry (70 to
90% exceedance), average (30 to 70% exceedance), moderately wet (10-30% exceedance), and
wet (0-10% exceedance). Flaming Gorge Dam spring peak release recommendations range from
3