7713

• UCREFRP Catalog Number: 7713
• Author: U.S. Fish and Wildlife Service, C. R. F. R. T.
• Title: Colorado Squawfish Recovery Plan.
• USFW Year: 1991.
• USFW - Doc Type: \
• Copyright Material: NO

Importance of Tributaries '
Tributaries of the Green and Colorado Rivers may be especially important to
the continued survival of the Colorado squawfish. Colorado squawfish '
historically or presently occupy tributaries of the Green and Colorado Rivers,
including the Yampa, Duchesne, White, Gunnison, Dolores, and San Juan Rivers
in the-Upper Basin, the Gila River and its tributaries, the Salt, Verde, and ,
other rivers in the Lower Basin. Tagging and telemetry studies indicate- the
Colorado squawfish moves long distances from spawning areas in the mainstem
Green River to feeding and overwintering areas in the Yampa, White, and

Duchesne Rivers (Miller et al. 1982a, 1982b, 1983; Radant et al. 1983; Tyus et '
al. 1982a, 1982b, 1987). Tyus (1986) suggested that tributaries play an
important role in the life history strategy of the Colorado squawfish and
perhaps serve to reduce intraspecific competition. '
Miller et al. (1982a) reported a net movement of juveniles from the Green
River to the White River, while Radant et al. (1983) documented movement of

adult fish between the White and Green Rivers and Green and Yampa Rivers '
during the spawning season. There also is a downstream movement of larval
Colorado squawfish from the Yampa River to the Green River (Haynes et al.
1984; Miller et al. 1982b; Tyus and Haines 1991). Furthermore, a net upstream
movement of adult and juvenile Colorado squawfish from the Green River into
the Yampa River has been suggested by Miller et al. (1982b) and Tyus (]986,
1990).
Colorado squawfish larvae have been collected from the Yampa River within
Dinosaur National Monument each year during the period 1980-88 (Nesler et al.
1988; Tyus and Haines 1991; Wick et al. 1981), and spawning migrations into
the lower Yampa were observed in 1981-88 (Wick et al. 1983; Tyus 1990).
Holden (1980) and Tyus and Karp (1989) indicated that flows from the Yampa
River were important to the recruitment of Colorado squawfish in the Green
River. Analysis of the hydrographs indicates that the Yampa River is the
primary contributor of high spring flows in the Green River which generally
exceeded 12,000 cfs at the Jensen gage. Spring flows of the Yampa River
affect the timing of Colorado squawfish spawning migrations (Tyus 1990).
Reasons for Decline '
Historically, the Colorado River was characterized as a river with wide
seasonal flow fluctuations (Waters 1946). It was known as Rio Colorado, the
great Red River of the West. Over 2,700 km (1,687 miles) long, it is cliff '
bound in canyons throughout much of its course. It drops over 3.2 km
(2 miles) in its journey to the Gulf of California, thereby creating some of
the most turbulent waters found on earth. At Lee's Ferry, Colorado River '
streamflows varied from 750 cfs in 1924 to an estimated 300,000 cfs in 1884
(White and Garrett 1988). Few rivers were so laden with silt. Averaging
0.62 percent silt content by volume, it formerly carried more than '
100,000 acre-feet (12,000 ha-meter) of soil to the Gulf of California each
year. It also is high in mineral salts: carbonates; sulfates; and chlorides
of calcium, sodium, and magnesium.

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