8188

• UCREFRP Catalog Number: 8188
• Author: Muth, R. T., et al.
• Title: Flow and Temperature Recommendations for Endangered Fishes in the Green River Downstream of Flaming Forge Dam.
• USFW Year: 2000.
• USFW - Doc Type: \
• Copyright Material: NO

Final Report

1-1

September 2000

FLOW AND TEMPERATURE RECOMMENDATIONS FOR ENDANGERED FISHES
IN THE GREEN RIVER DOWNSTREAM OF FLAMING GORGE DAM

by

Robert T. Muth, Larry W. Crist, Kirk E. LaGory, John W. Hayse,
Kevin R. Bestgen, Thomas P. Ryan, Joseph K. Lyons, Richard A. Valdez

1 INTRODUCTION

The Green River system of the upper Colorado River basin in Utah and Colorado supports
populations of three endangered fishes - humpback chub Gila cypha, Colorado pikeminnow1
Ptychocheilus lucius, and razorback sucker
Xyrauchen texanus - and it historically
supported the endangered bonytail Gila
elegans (U.S. Fish and Wildlife Service
[USFWS] 1994). Specifically, the system has
two of the remaining six populations of
humpback chub (USFWS 1990a; Valdez and
Rye11995, 1997), the largest populations of
Colorado pikeminnow (USFWS 1991a), and
the largest riverine population of razorback
sucker (USFWS 1998a). One of the last
reported concentrations ofbonytail was in the
Green River within Dinosaur National
Monument, and the species may still exist in
the system in extremely low numbers
(USFWS 1990b). Consequently, the Green
River system is considered vital to recovery
of these federally protected species. The
Green Ri ver downstream of the Yampa River
confluence and portions of the Yampa, White, and Duchesne Rivers have been designated as critical
habitat under provisions of the Endangered Species Act, as amended (USFWS 1994).

Endangered species - A species that is in danger of
extinction throughout all or a significant portion of its
range.

Threatened species - A species that is likely to
become endangered within the foreseeable future
throughout all or a significant portion of its range.

Critical habitat - The specific areas within a
geographical area occupied by a threatened or
endangered species, at the time it is listed, containing
those physical or biological features essential to the
conservation of the species and which may require
special management considerations or protection. May
also include areas outside the geographical area
occupied by the species, at the time it is listed, upon
determination by the Secretary of the Interior that such
areas are essential for the conservation of the species.

Systemwide reductions in spatial and temporal components of habitat complexity, attributed
to past and ongoing alterations in river flow and temperature, have been implicated as major factors
contributing to decline of the endangered fishes (Stanford 1994). Operation of Flaming Gorge Dam,
which is located on the upper main-stem Green River, strongly influences downstream flow and

lColorado pikeminnow is the currently accepted common name for Ptychocheilus lucius, formerly known as
Colorado squawfish (Nelson et al. 1998).