7823

• UCREFRP Catalog Number: 7823
• Author: Miller, W. H., et al.
• Title: Colorado River Fishery Project, Part II, Final Report, Field Investigations.
• USFW Year: 1982.
• USFW - Doc Type: \
• Copyright Material: NO

valley. The Duchesne River enters near Ouray, Utah, draining the south-
ern slope of the Uinta Mountains. The White River enters below the mouth
of the Duchesne, having its headwaters on the western slope of the
Rocky Mountains. Below these principle tributaries, the Green proceeds
120 miles, (193 kilometers) through Desolation and Gray Canyons. The
Price River enters the Green in lower Gray Canyon. The Green River then
enters the Green River Valley near the town of. Green River, Utah. The
San Rafael River enters the Green about 25 miles (40 kilometers) below
the town of Green River. The Green River then proceeds south through
Labyrinth and Stillwater Canyons in Canyonlands. National Park to join the
Colorado River. During its course, the Green River drops from about
14,000 feet (4,300 meter) near its source to about 4,000 feet (1,200
meters) at its mouth, a 10,000-foot (3,000-meter) drop in elevation.
Historically, the Colorado River has been characterized by great
seasonal fluctuations, high turbidities, highly fluctuating temperatures,
and high dissolved solids. The fish fauna of the Colorado River evolved
in such conditions and are adapted to them. However, changes occurring
in the basin have severely altered the aquatic system. These include
the construction of reservoirs, flow diversions, consumptive use, and
the introduction of exotic (i.e. introduced, non-native) species.
The geological history of the upper Colorado River Basin is re-
counted from exposed deposits ranging from Precambrian to recent.
John Wesley Powell (1961) explored the Green River in 1896, described
the geologic origin of the river. The existing system has persisted
since the Pliocene epoch and has been isolated with surrounding basins
• for millions of years (Behnke and Benson, 1980). This period of isola-
tion has been reflected in the fish fauna and Carlson and Carlson (1982)
stated that although Homo sapiens dates back to about 35,000 years,
fossils of Gila and Ptychocheilus similar to our existing native fishes
(Miller 1958) have been traced to the middle Pliocene, or about 8 million
years ago.
Climatic conditions in the upper Colorado River Basin are highly
variable. This is reflected in a precipitation range from about
50 inches (1.3 meters) in the mountains to less than 6 inches
(0.2 meters) in the arid valleys. Iorns et al. (1965) indicated a
contrasting climate between wet, cool, high mountains; drier plateaus and
low mountains with widely fluctuating temperatures; and dry interior
valleys which are hot in summer and very cold in winter. These condi-
tions result in a mixture of plant communities .in the Green subbasin
ranging from alpine meadows and subaipine and montane forest; mountain
brush, pinyon-juniper forests; sagebrush, greasewood; and grassland
communities.
Objectives
The objectives of this study were provided in the joint Bureau
of Reclamation (BR) - Fish and Wildlife Service (FWS) Memorandum of
Understanding (MOU), dated April 16, 1979 (Contract No. 9-07-40-L1016).
Primary emphasis was directed toward habitat requirements and life
history information for endangered fishes; Colorado squawfish
(Ptychocheilus lucius) and humpback chub (Gila cypha). Since then the
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