7394

• UCREFRP Catalog Number: 7394
• Author: Grabowski, S. J. and S. D. Hiebert.
• Title: Some Aspects of Trophic Interactions in Selected Backwaters and the Main Channel of the Green River, Utah 1987 - 1988.
• USFW Year: 1989.
• USFW - Doc Type: Denver, Colorado.
• Copyright Material: NO

METHODS AND MATERIAL

Study Area

Three widely separated areas in an 84-mile reach of the Green River, near
Vernal, Utah, with a range of backwater types and with previously reported
differing populations of larval Colorado squawfish were selected for the study
with assistance of USFWS and USBR personnel. The three study areas were
located at Island Park in Dinosaur National Monument, at Jensen downstream
from the Route US 40 bridge over the Green River, and at Ouray on the Ouray
National Wildlife Refuge (fig. 1). Previous studies by the USFWS and the Utah
Department of Natural Resources indicated increasing abundance of larval
Colorado squawfish in backwaters downstream from Island Park to Ouray.
Abundance of larval Colorado squawfish was greatest in Ouray area backwaters.

In 1986, USFWS personnel familiar with the river designated certain backwaters
that apparently persisted from year to year as "reference" backwaters,
cnadidates for long-term study. They also defined five categories of
backwaters, including ephemeral, deep side channel, tributary, wash, and
flooded bottom. In 1987, the "reference II 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). Garden Creek backwater was initially large but decreased
substantially in size as river flows decreased during the summer and
eventually became the "small" backwater at Island Park. Initially the small
backwater was a backwater off a side channel of the river; this backwater
dried up as riverflows dropped, resulting in a cut-off side channel. This was

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