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

captured in a single year (2003) in the 2002 to 2004 period, when substantially more non-native
taxa were captured than in previous years.
The proportion of native fishes was 50% or less in samples in each year in the 2002 to
2004 period. Native taxa numbers in all years were dominated by flannelmouth sucker and
bluehead sucker, particularly in 2003, and fewer numbers of speckled dace and very few (n = 3)
early life stage roundtail chub were collected, and only in 2003. In all samples, mountain
whitefish specimens were juveniles > 50 mm TL.
Large increases in non-native fish in 2002 to 2004 drift net samples were mostly because
of increased abundance of non-native cyprinids and white suckers. In 2002, the large increase
in the number of fish collected was due to red shiner, and those were mostly large juveniles and
adults. In 2003 and 2004, sand shiner, red shiner, and white sucker were the most common non-
native taxa. We also collected young (N = 6, 10 to 24 mm TL) smallmouth bass in drift samples
in 2003, and greater numbers in 2004 (N = 93, 8 to 28 mm TL), but none in 2002. Those small
smallmouth bass represent the first documented reproduction in Lodore Canyon.
In 2003, most fish (60%) were captured the day of and the day following two turbidity
events, one on 22 July and one on 6 August. The 22 July 2003 event was especially severe, as
water clarity was reduced to zero and silt loads were extremely high from runoff in the
Vermillion Creek drainage basin. Most bluehead sucker (53%) and flannelmouth sucker (66%)
captured that year were taken during these events, as were most smallmouth bass (4 of 6) and
sand shiner (74%). About 34% of red shiner captured that year were taken during these two
events. We noted relatively high mortality of those fish in drift net samples collected on 22 July;
usually fish collected in drift nets are alive upon capture and larger suckers present in mid- to
late-July are noticeable. Thus, loss of visibility and outright mortality from sediment loads may
be factors associated with increased transport rates.
A similar high turbidity and increased flow event occurred on 17 July 2004, when a total
of 532 fish of all species (29% of all captured in 2004) were captured. All 2004 smallmouth bass
specimens were captured in the period 17 to 25 July, 87 of 93 (94%) on 17 July. Flow stage
dropped 7 to 8 cm the next day, but turbidity remained high for several days. On 25 July, a
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