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

581), and a 1.6-km-long lower Lodore Canyon site near Alcove Brook (RK 561). To make fish
composition data from their fixed sites comparable to more recent data (Bestgen and Crist 2000,
this study), we used a subset of our samples collected in a 4.8 RK reach encompassing their fixed
stations. The more recent samples were used only if the sampling segment ended within the
reach; samples started within the reach that ended outside of it were not used. We combined
seine and electrofishing data in each of the 1994 to 1996 and the 2002 to 2004 periods for
comparisons to be consistent with Holden and Crist (1981). Changes in species composition
among the three periods (1978 to 1980, 1994 to 1996, 2002 to 2004) were assessed by
comparing the number and relative abundance of native and introduced species captured in each
period. Differences in habitat availability, collecting gear, and sampling effort may affect
assessments of faunal differences among the three periods. Therefore, our qualitative
assessments of temporal change for those reaches were conservative, but supported by
concurrently considering broader spatial scale patterns of changes in fish distribution and
abundance throughout Lodore Canyon.
RESULTS AND DISCUSSION
Effects of Flaming Gorge Dam on Green River discharge and temperature patterns,
Lodore Canyon.-Four major dam-related events affected physical habitat and the fish
community of the upper Green River: dam installation in 1962, penstock modification in 1978,
flow re-regulation beginning in 1992, and higher peak flows, lower base flows, and drought
events since 1997. Prior to construction of Flaming Gorge Dam, discharge patterns of the Green
River exhibited high spring peaks followed by lower, stable base flows in other seasons,
particularly winter (Fig. 2). Water temperature ranged from a low of 0°C in winter to over 22°C
in summer (Fig. 3) and turbidity increased seasonally from inputs of fine inorganic silts (Vanicek
et al. 1970). Immediate dam effects included inundation of riverine habitat in the reservoir zone.
Downstream, naturally variable and relatively high spring discharge maxima were reduced (Fig.
4). Power plant operations increased base flow levels and daily discharge fluctuations.
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