7047

• UCREFRP Catalog Number: 7047
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes in the Green River, Utah
• USFW Year: 1991.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

further complicated because of limited life history information. Habitat use
of endangered fishes may only reflect temporary, seasonal, or marginal habitat
availability. Thus, caution must be exercised when determining habitat needs
and limiting factors for fishes in decline, and professional biological
judgement must be recognized as critical in data interpretation. We stress the
need for system-level cognizance and interpretation in evaluating factors that
are potentially limiting species in decline; e.g., a high number of an
endangered species in one restricted location may not justify its delisting.
Based on professional interpretation of the best available data, we
consider the following flow and non-flow related measures as important for
recovery of listed Colorado River fishes in the Green River basin. These are
presented by time of year and species.
Spring (March 21-June 21)
Colorado squawfish
Adult Colorado squawfish utilize inundated shorelines and lowlands during
spring. This natural lowland inundation, and the increased availability of
food and habitat is viewed as important for physiological conditioning. Use of
these habitats may mitigate some of the affects of winter stress, and aid in
offsetting the large energy expenditure required for migration and spawning.
Less-than-annual spawning observed in the fish may be associated with adverse
winter/spring conditions.
Migration is an important component in the reproductive cycle of Colorado
squawfish and migration routes must be protected and barriers discouraged. We
consider migration cues such as high spring flows, increasing river
temperatures, and possible chemical inputs from flooded lands and springs as
important to successful reproduction. The duration, magnitude, and timing of
spring runoff also affects spawning substrates,-and formation of eddy
habitats used by staging fish. High spring flows mobilize nutrients and
sediments, and aids in forming nursery habitat. Ground and surface water in
the spawning areas may provide orientation/piloting cues. High and/or erratic
flows in early spring (March-April) may adversely affect backwater habitats to
the detriment of young Colorado squawfish.
Reduced spring runoff may aid growth of the introduced saltcedar and other
plants which invade flood zones, trap sediments, and thereby increase bank
stabilization. This can decrease habitats of young Colorado squawfish and
other native fishes while increasing habitat and providing environmental
conditions that are more suitable for some introduced fishes.
Humpback chub
The availability and suitability of rocky, canyon-bound habitat used by
humpback chub may be adversely affected by the present alteration of spring.
runoff in the Green River. Spawning of humpback chub occurs shortly after
highest spring discharge at river temperatures of about 20°C in the Yampa
River, and presumably in Gray Canyon area of the Green River. Flow effects on
the availability of shoreline eddy habitat, bank stabilization due to exotic
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