8022

• UCREFRP Catalog Number: 8022
• Author: Muth, R. T., et al.
• Title: Reproduction and Early Life History of Razorback Sucker in the Green River, Utah and Colorado, 1992-1996.
• USFW Year: 1998.
• USFW - Doc Type: 34,
• Copyright Material: NO

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fish larvae under varied Green River discharges during our annual sampling periods. The latter
included ephemeral shoreline embayments (e.g., backwaters) and particularly ponded lower
sections of flooded tributary streams, side canyons, washes, canals, or channels, These habitats
generally persist through at least mid-summer and are primary nursery areas for fish larvae in
spring and early summer under the present regulated flow regime of the Green River.
Collections were concentrated in the Escalante, Jensen, and Ouray reaches (C, D, and E)
of the middle Green River and in the lower two reaches (G and H) of the lower Green River
(Figure 1). Sites within reaches C-E that were intensively sampled on a regular basis throughout
the investigation included Cliff Creek (an intermittent tributary stream joining the Green River at
RK 487.5, Escalante), Stewart Lake Drain (an outlet canal from Stewart Lake at RK 481.7,
Jensen), Sportsmans Drain (an outlet canal from Unitah Sportsmans Club Lake at RK 477.4,
Jensen), Greasewood Corral (a side channel at RK 405.6, Ouray), and the inlet canal to the Old
Charlie Wash managed wetland (Mod de 1997) at RK 405.4, Ouray. Established sampling sites
in reaches G and H included washes and backwaters at or just upstream or downstream from the
mouth of the San Rafael River (RK 152.1-156.2, reach G), and Millard Canyon (RK 53.9), a
wash-backwater-side channel complex at Anderson Bottom-Bonita Bend (RK 49.9-50.7), and
Holeman Canyon (RK 45.1) in the middle Stillwater Canyon reach (H). Sampling in reaches A
(Echo Park) and B (Island-Rainbow Park) ofthe middle Green River was mostly opportunistic
and occurred at irregular intervals during the investigation. Backwaters and washes in the Green
River Valley reach (F) of the lower Green River were sampled in 1996 primarily to assess
transport of razorback sucker larvae into the lower Green River from the middle Green River.
Flooded and backwater habitats had low or no water velocity, and typically had
predominantly silt and sand or silt and mud substrates and sparse to dense emergent macrophytes
near shoreline. These habitats generally averaged less than 1 m deep, were moderately turbid,
and often had low-velocity eddies at their interface with the main channel. Water temperatures in
these habitats at sunrise and in late afternoon or early evening were routinely recorded only on
sampling dates in 1996. Sunrise temperatures ranged from 15 to 230C (mean, 180C) in the
middle Green River and from 11 to 280C (mean, 180C) in the lower Green River. Temperatures

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