8182

• UCREFRP Catalog Number: 8182
• Author: Bestgen, K. R. and L. W. Crist.
• Title: Response of the Green River Fish Community to Construction and Re-regulation of Flaming Gorge Dam. 1962-1996\
• USFW Year: 2000.
• Copyright Material: NO

redside shiner were rare or very rare in reaches 1 through 3. Abundance of native fishes,
particularly flannelmouth and bluehead suckers and speckled dace, increased dramatically.
A distinct "break" in the Lodore Canyon fish community occurred in reach 4, where the
cool-water tolerant community was replaced by one dominated by warm-water species. In reach
4, sand and red shiners first appeared in large numbers, and fathead minnow and redside shiner
were once again abundant. Re-appearance of abundant fathead minnow and redside shiner
populations in reach 4 of Lodore Canyon was likely a response to increased availability of low-
velocitybackwater habitat compared to upstream reaches 1 through 3. The substantial numbers
of red and sand shiners found in reach 4 was likely also a threshold response to warmer water
temperatures. Although no detailed habitat assessments were conducted, most seine samples in
reaches 1 through 3 were from eddies and low velocity channel margins; sandy-bottomed
backwaters were found almost exclusively in reach 4. Red and sand shiners remained rare or
non-existent in reaches 1 through 3 since 1980 and were very rare in Browns Park despite access
and presence of backwaters. Native fish species richness in reach 4 was similar to upstream
reaches, but their relative abundance was much reduced.
Longitudinal changes in the Lodore Canyon fish community, electrofishing samples.--
Sampling with electrofishing gear in Lodore Canyon revealed essentially the same patterns
observed for seine sampling data--more cold- or cool-water tolerant species upstream and a more
species rich fish community composed of cool- or warm-water taxa downstream. Relative
abundance of native fishes was reasonably even throughout reaches 1 through 4 and ranged from
51 to 63 % of the fishes captured. This suggested that habitat for adults of most of those
dominant native fishes was evenly distributed throughout Lodore Canyon. Common carp, which
occupied mainly slow eddies and deep backwaters, were relatively uncommon in reaches 2 and 3
where those habitats were uncommon.
Increased relative abundance offish with small body size in downstream reaches of
Lodore Canyon maybe due to increased habitat diversity, namely more shallow riffles. Prey of
suitable size (s 300 mm TL) for adult northern pike and Colorado pikeminnow were most
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