7165

• UCREFRP Catalog Number: 7165
• Author: Miller, W. H., H. M. Tyus and C. A. Carlson.
• Title: Fishes of the Upper Colorado River System
• USFW Year: 1982.
• USFW - Doc Type: Present and Future.
• Copyright Material: NO

Fishes of the San Rafael River system were
discussed by McAda et at (1980). Native fishes were
dominant in the tributary streams and middle sec-
tion of the San Rafael River, while introduced fishes
were dominant near the mouth of the river.
Fishes of the Upper Main-stem Colorado
Sub-basin
Joseph et at (1977) considered native and in-
troduced fishes of the Upper Main-stem Colorado
and factors affecting area streams. Introduction of
non-native fishes and waterflow reductions were the
main factors involved in declines of native species,
and oil shale development will surely add another
major obstacle to their survival.
The Gunnison River at one time contained all
threatened or endangered fishes of the Upper Col-
orado System except the Kendall Warm Springs
dace and the humpback chub. With the introduction
of non-native fishes, the abundance and distribution
of these native fishes was drastically curtailed
(Joseph et at 1977). Part of the Gunnison River was
once a world-famous trout fishery. Wiltzius (1978)
reviewed many studies done on the Gunnison after
1927 and discussed the quality and quantity of the
trout fisheries since the 1880's. Introduction of
several species, together with continued stocking
and other factors, played a role in changing the fish
fauna. Wiltzius also considered the effects of Blue
Mesa and Morrow Point reservoirs on the fishery of
the Gunnison. The fisheries in the tailwaters of
dams forming these and other major reservoirs in
the Upper Basin were discussed by Mullan et at
(1976).
Holden and Stalnaker (1975b) discussed the native
and introduced fishes of the Dolores, including their
abundance and distribution. The Dolores River
System appeared to have little importance regard-
ing preservation of rare and endangered fish species
and was far from its natural state due to irrigation
and severe pollution.
General notes on fishes of the Upper Main-stem
Colorado near Moab, Utah, were provided by Taba
et at (1965). Holden and Stalnaker (1975a) collected
near Moab, at three other sites on the Upper Main-
stem Colorado, and at one station on the Gunnison
River.
Fishes of the San Juan Sub-basin
Joseph et at (1977) stated that many of the native
large-river endemics of the San Juan River were
much reduced in distribution and abundance and
that some were probably extirpated. Navajo Dam
construction appeared to exert the major impact,
and competition from introduced species was
another significant factor. Koster (1960) and Minck-
ley and Carothers (1979) reported Colorado
squawfish captures from the San Juan River.
Fish encountered in the Glen Canyon area on the
Colorado River before construction of Glen Canyon
Dam included 17 species; only six were native
(Woodbury 1959). Major faunal collections came
from the tributaries as the river at this point was
rapid, showing much scouring and providing little
habitat for flora and fauna.
Water impoundment behind Glen Canyon Dam
began in January 1963. Largemouth bass were
stocked in the resultant Lake Powell in 1963 and
1964, and abundant stocks have been maintained by
natural reproduction (Miller and Kramer 1971).
Rainbow trout were also introduced in 1963; yearly
stocking continued but in later years was restricted
to the lower reservoir (May 1973). Introduction of
other fishes occurred in part to provide an abun-
dant, vulnerable food source for the four major cen-
trarchids (largemouth bass, black crappie, bluegill,
and green sunfish) in the reservoir (May and Thomp-
son 1974; May et at 1975). All resident species ex-
perienced changes in their food habits as feeding on
introduced threadfin shad increased. Introductions
of striped bass in 1974 and 1975 have provided
another species to the fishery. May and Gloss (1979)
studied depth distribution of major gamefishes in
Lake Powell in relation to oxygen and temperature
profiles. They referred to earlier, largely-
unpublished research on physical, chemical, and
biological characteristics of the reservoir. Diversity
of habitat in Lake Powell and of its community of
endemic and introduced fishes was emphasized. Pot-
ter (1980) provided an ecological description of Lake
Powell, stressing management of the resource.
Holden and Stalnaker (1975a) collected just below
Glen Canyon Dam and reported on fishes of that
area. Minckley and Carothers (1979) reported collec-
tion of razorback suckers near the mouth of the
Paria River.
ACKNOWLEDGEMENTS
We greatly appreciate reviews of drafts of this
paper by Robert Behnke, Harold Tyus, and William
Miller. The assistance of Darrel Snyder was par-
ticularly helpful.
5