7103

• UCREFRP Catalog Number: 7103
• Author: Grabowski, S. J. and S. D. Hiebert.
• Title: Green River Trophic Dynamics Study 1987
• USFW Year: 1988.
• USFW - Doc Type: Draft.
• Copyright Material: NO

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METHODS AND MATERIALS

Study area

Three study areas with previously reported differing populations of
larval Colorado squawfish were chosen. These three areas were roughly
one-mile in length and were located at Island Park in Dinosaur National
Monument, at Jensen downstream from the Route U.S. 40 bridge over the
Green River, and at Ouray on the Ouray National Wildlife Refuge (fig. 1).
Previous studies by the USFWS indicated increasing abundance of larval
Colorado squawfish downstream from Island Park to Ouray. Abundance
of larval Colorado squawfish is apparently greatest in the Ouray area.

In 1986, USFWS personnel designated certain backwaters that apparently
persisted from year to year as "reference" backwaters. In 1987, the
"reference" backwater at Island Park did not develop, however, so a
main river site and two backwaters were selected upstream near the
confluence of Garden Creek (BA-332.2) and at Big Island (BA-333.2).
The Garden Creek backwater was initially large but was greatly reduced
in size as river flows decreased during the summer and essentially
was the "small" backwater for comparison at Island Park. Garden Creek
backwater is at RMI (River Mile Index) 332.2. Initially the small
backwater was a backwater off a side channel of the river; this backwater
dried up as riverflows dropped, cutting off the side channel and

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