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

abundance or remained rare over the three study periods; speckled dace and roundtail chub
showed particularly large declines. Ten introduced taxa increased in abundance, rainbow trout
declined in abundance, and five others remained similar in abundance between the two earliest
periods. Largest increases were by fathead minnow, sand shiner, white sucker, and hybrid
suckers. Between the 1994 to 1996 and 2002 to 2004 periods, fathead minnow, redside shiner
and all salmonids declined, and sand shiner and red shiner increased dramatically.
Species composition shifts at both sites suggested a progressive shift from a cold water
fish community to one dominated by cool-water or warm-water taxa, with non-native warm water
fish progressively invading and establishing upstream. The number of fish in samples in each of
the upper and lower Lodore Canyon sites in the two earlier periods was similar, but more fish
were sampled in the later 2002 to 2004 period. Although the likely reason for the increase is due
to a larger number of seine samples in the last period, we feel as though the overall trends are
reflective of the entire fish community and not due just to increased sampling in backwaters.
This limited data set of electrofishing and seine captured fish at these two Lodore Canyon
sites showed an opposite trend of declining incidence of hybrid suckers compared to canyon-wide
data collected in the same period. We believe this is an artifact of combining data using different
gear types, because increased abundance of seine-collected small-bodied fish in the recent sample
reduced the percent composition of hybrids, which are most commonly detected among the fewer
relatively large-bodied fish.
SUMMARY
A main tenet of dam re-regulation to create more natural flow and temperature regimes is
that native fishes will benefit (Stanford et al. 1996, Poff et al. 1997, Muth et al. 2000). The data
sets presented here were used to evaluate that hypothesis.
Flow and temperature effects on the Green River fish community between 1994 to 1996
and 2002 to 2004.-Evaluating biotic response to flow and temperature recommendations is a
considerable challenge given the multitude of factors that can affect the distribution and
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