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

vegetation overgrowth, and abundance of channel catfish and other potential
competitor and predator non-native fishes, presumably influences humpback chub
habitat in the Green River. The few captures of humpback chub in Whirlpool
Canyon in recent years (relative to earlier decades) indicates a general
decline of Gila in that system. This may be due to cooler temperatures,
changes in the aquatic food base, and other influences of Flaming Gorge Dam
operations.
Razorback sucker
Razorback suckers spawn in the Jensen area of the upper Green River and
utilize the increasing and highest spring flows that are maintained by runoff
from the Yampa River. Curtailment of spring runoff in the mainstream Green
River downstream from Flaming Gorge Dam has been associated with the loss of
recruitment in this species. Flooding of lowlands during spring runoff is
considered beneficial to adults and may be important for dispersal and rearing
of young. Shallow, flooded areas also heat more rapidly than the river, and
thus may provide more favorable rearing conditions. Flaming Gorge releases
should provide spring flooding of spawning areas and lowlands to aid in
reestablishment of razorback sucker. Influence of spring flows on razorback
sucker spawning, recruitment, growth, and survival 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 believed important 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 flows and other parameters
and spawning need further evaluation with respect to low, average, and high
water years. Historic flows near 56.6 m3/s in late summer and autumn are
correlated with availability of nursery habitat, young fish abundance and
growth. Abnormally high flows from Flaming Gorge have resulted in a loss of
habitat and significantly low standing crops of young fish. Flows associated
with maximizing backwater habitat (quantity and quality) in the Green River
should be provided. Daily water fluctuations associated with power releases
may strand fish, lower backwater productivity, and encourage the encroachment
of woody vegetation in the floodplain. The relationship between daily flow
fluctuations in the upper Green River and quality and quantity of shoreline
habitats used by young Colorado squawfish should be more fully evaluated.
29