9678

• UCREFRP Catalog Number: 9678
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1990.
• USFW - Doc Type: Flaming Gorge Studies - Draft Consolidated Report Preliminary.
• Copyright Material: NO

flows on razorback sucker spawn in the Green River should be more fully
evaluated.
Summer (June 22-September 22)
Colorado squawfish
Gradually decreasing flows (as typical of the historic hydrograph),
maintenance of sediment transport regimens, and warming river temperatures of
early and mid-summer are necessary for successful spawn, hatching, and
downstream transport of drifting larvae. The gradual decline of summer flows
following spring scouring maintains natural sediment transport equilibria,
prevents siltation of spawning substrate, aids downstream drift of larvae, and
creates productive nursery areas. Erratic and unseasonal high or low flows
could disrupt larval transport, strand larvae, and alternately flood and
dewater nursery habitats. Relationships between these and other parameters
(e.g., type water year) and spawning need further ,evaluation with respect to
low, average, and high water years.
Humpback chub
Rapidly declining summer flows could adversely affect spawning and nursery
habitat in canyon-bound reaches by concentrating fishes in suboptimal habitats
and increasing the potential for disease, competition, predation and
hybridization. Gradually declining flows following peak spring runoff is
desired. Low flows and associated higher water temperatures may aid growth of
channel catfish, a potential competitor and predator of humpback chub.
Razorback sucker
Recruitment failure of razorback sucker presumably occurs in late spring and
early summer. This failure has been linked elsewhere with predation by
introduced fishes (including common carp and channel catfish), but may also be
associated with loss of warm, flooded bottomlands and reduced river
temperatures. Lower spring flows may favor growth and proliferation of
potential predators.
Autumn and Winter (September 23-March 20)
Colorado souawfish
Historic flows near 56.6 m3/s in late summer and autumn are correlated with
availability of nursery habitat, young fish abundance and growth. Flows
associated with maximizing backwater habitat (quantity and quality) in the
upper Green River should be determined using both Yampa and Green river
flows. Unusually high flows in the late summer and autumn reduce availability
of nursery habitat for young Colorado squawfish. Stable winter flows reduce
ice scouring of shoreline habitats used by adults and young and may reduce
stress to the fish associated with induced movements.
Humpback chub
Habitat use and flow needs of the humpback chub during autumn and winter are
not well understood, but observations in the lower Yampa and Green rivers
during low-flow events noted that Gila species (and channel catfish) were
constrained to pools and semi-isolated eddies. Unusually low-flow conditions
in the autumn and winter should be avoided.
Razorback sucker
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