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

Gila spp. consumed larval fish. After Colorado squawfish become piscivorous,
red shiners, fathead minnows, occasional catostomids, and other introduced
fish species are found in the diet suggesting less dependence on the
relatively abundant chironomid larvae.

Observations from qualitative seine hauls used in this study to collect fish
for food habit studies, revealed young Colorado squawfish in Jensen and Ouray
backwaters, with more fish observed in shallow (about 0.3 m deep), more turbid
backwaters having a relatively wide connection to the river. Bottom
composition of these shallow backwaters was generally muck or gyttja, often
with organic material and some sand.

Shallow backwaters with a large surface area in the Ouray area that were
seasonally permanent after runoff subsided were generally warmer compared to
upstream backwaters at Island Park and Jensen; they had higher concentrations
of nutrients, particulate organic material, and greater densities and weights
of benthic macroinvertebrates, and moderate chlorophyll i levels. Benthic
macroinvertebrates were the principal food source for most young fish, except
suckers. The river is one nutrient source for backwaters. Increased
concentrations of some nutrients in the river at Ouray compared to Jensen,
result from upstream agricultural runoff and return flows.

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