7422

• UCREFRP Catalog Number: 7422
• Author: Valdez, R. A. and W. J. Masslich.
• Title: Winter Habitat Study of Endangered Fish - Green River.
• USFW Year: 1988.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

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DRAFT

1.0 INTROOOCTlOO

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This document is the Final Report subfidtted to the Bureau of Reclamation (BOR)
for Contract No. 6-CS-40-04490, entitled "winter Habitat study of Endangered
Fish - Green River". This report integrates the results of a two-year study
(1986-87 and 1987-88) of winter habitat use by the imperiled Colorado squawfish
and razorback sucker. The results of this investigation are recommended flow
releases for Flaming Gorge Dam for the months of November through March.

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1.1 OBJECTIVES

The objectives of this investigation are to:

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1.

Determine if adult Colorado squawfish and razorback suckers
remain in specific river segments from fall to early spring
in the Green River from the OUray Refuge to Browns Park.

2.

Describe microhabitat (depth, velocity, substrate, cover
and temperature) used by adult Colorado squawfish and
razorback sucker during the winter months (NOvember through
March) .

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3. Develop winter habitat utilization curves based on
microhabitat data collected during the study (Bovee, 1986).

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4. Relate Physical Habitat Simulation (PHABSIM) data output,
and habitat utilization curves developed in item 3 above,
to actual use patterns by Colorado squawfish and razorback
suckers observed in the field, and evaluate weighted
useable area using the Instream Flow Incremental
Methodology (IFIM) (Bovee, 1982). This includes computer
analysis of thePHABSIM effort following calibration of
each instream flow station by the u.s. Fish and wildlife
Service (FWS). This objective is to be accomplished after
the second year of field investigations, 1987-88.

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1.2 BACKGROOND

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This investigation was conducted as part of BOR's ongoing program on endangered
fishes of the upper Colorado River basin. That program is part of the
responsibility of federal agencies as prescribed by the Endangered Species Act
of 1973, as amended in 1978, to protect and, where possible, to promote the
recovery of these fishes.

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Since 1978, intensive investigations have been conducted to collect biological
information on the endangered fishes of the Green and Colorado river systems.
These investigations, principally funded by BOR, have been undertaken to
develop a better understanding of the physical and biological needs of the
endangered Colorado squawfish (Ptychocheilus lucius), humpback chub (Gila
cypha) and bony tail chub (Gila elegans), as well as the federal candidate
species razorback sucker (Xyrauchen texanus). A major portion of this effort

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