9549

• UCREFRP Catalog Number: 9549
• Author: Bestgen, K. R., K. A. Zelasko, R. I. Compton and T. Chart.
• Title: Response of the Green River Fish Community to Changes in Flow Temperature Regimes from Flaming Gorge Dam since 1996 based on sampling conducted from 2002 to 2004.
• USFW Year: 2006.
• USFW - Doc Type: 115,
• Copyright Material: NO

Stream flow and water temperature data collection and presentation.-Most temperature
data were from lower Lodore Canyon and Mitten Park (pers. comm., G. Smith, U. S. Fish and
Wildlife Service, Denver, Colorado). Flow data were from U. S. Geological Survey gauges.
First, we describe the major changes in flow and temperature regimes in Lodore and Whirlpool
canyons as a result of construction and operation of Flaming Gorge Dam. We characterized flow
differences in the historical period (Lodore Canyon, Greendale gauge, # 09234500, 1951 to
1962; Whirlpool Canyon, Jensen gauge # 09261000, 1946 to 1962), a post-impoundment period
(1962 to 1991), a post-Biological Opinion period (1992-1996), and a recent (1997 to 2004)
period which was thought to represent conditions that affected the fish communities during this
investigation. We used the Jensen, Utah gauge to characterize Whirlpool Canyon and Island-
Rainbow Park flows because the few small tributaries present between Whirlpool Canyon and
the downstream gauge will not affect flow estimates appreciably.
Fish sample data analysis and presentation.-Composition of the fish community in the
study area (Fig. 1) was calculated for samples collected in the 2002 to 2004 period for each gear
type. Longitudinal and temporal shifts in community composition were characterized by
partitioning samples into reaches both for small-bodied fishes captured primarily by seining and
for large-bodied fishes captured primarily by electrofishing in the periods 1994 to 1996 and 2002
to 2004. Samples were from eight contiguous Green River reaches: a Browns Park reach, four 8-
RK Lodore Canyon reaches, upper and lower Whirlpool Canyon reaches (9 and 8 RK) and the
Island-Rainbow Park reach (10 RK); electrofishing samples were collected only in Lodore and
Whirlpool canyons.
Change in numerically dominant native and non-native fishes in reaches was compared
among study periods 1994 to 1996 and 2002 to 2004 and reaches to facilitate detection of
longitudinal shifts in community composition. We defined relative abundance as the percent
composition that a particular species represented in a sample. For seine samples, catch-per-unit-
effort (CPUE) was number of fish of a particular species divided by area sampled per seine haul
(density). For electrofishing samples, CPUE was number of fish captured per amount of time
sampled. For trammel net samples, CPUE was fish captured per net hr. We did not measure
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