7715

• UCREFRP Catalog Number: 7715
• Author: U.S. Fish and Wildlife Service, C. R. F. R. T.
• Title: Bonytail Chub Recovery Plan.
• USFW Year: 1990.
• USFW - Doc Type: \
• Copyright Material: NO

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introduction program were to monitor fish behavior and collect habitat use
information for future introduction programs. A total of 35 adult bony tail
chubs were implanted with radio transmitters and released during three
different seasons at Island Park in Dinosaur National Monument and at Jensen,
Utah. Preliminary results of the effort suggest hatchery or pond-raised
adult ma h .. ada ting to rive' . nts. However, the
introduction program will be eva ua e at the end of the first year by the
respective agencies and, if necessary, modified.

Reasons for Decline

Miller (1961) indicated that decline of the bony tail chub in the Gila River
system during the first half of the 20th century may have been due to habitat
degradation as a result of overgrazing of grassland and riparian vegetation
and poor land management practices, depletion of ground water, construction of
dams, flow depletions from irrigation and mining, and introduction of
nonnative species. By the early 1900's, much of the lower Gila River was dry.
Droughts in the late 1800's and prolonged flooding in the early 1900's
stimulated the need for flood control and storage of irrigation water on the
mainstem Colorado River and its major tributaries (Fradkin 1981). Hoover
(Boulder) Dam (Lake Mead) was built in 1935, Parker Dam (Lake Havasu) in 1938,
and Davis Dam (Lake Mohave) in 1950, all on the Colorado River. Roosevelt Dam
was constructed on the Salt River in 1913, followed by the Coolidge Dam on the
Gila River in 1928, and other structures on the Salt and Verde rivers between
1925 and 1945 (Rinne 1975). Construction of these dams transformed much of
the mainstem Colorado River and some of its major tributaries into either
lacustrine environments, dry riverbeds, or rivers with flow and temperature
regimes greatly altered from historic conditions. These changes are believed
to be a major cause of decline of the bony tail chub in the Lower Basin.

Decline of the bony tail chub in the Upper Basin occurred more recently, but is
similarly related to water resource development and associated habitat loss
and modification. Vanicek et al. (1970) concluded that reduction in the
numbers and species of native fishes in the Green River trom Flaming Gorge Dam
to the mouth of the Yampa River was due to the lower water temperatures and
altered annual flow and temperature regimes occurring after the dam's closure
in 1962. This is partially substantiated by laboratory studies by Hamman
(1982b) and Marsh (1985), who demonstrated that temperatures lower than 130C
(550F) significantly reduces hatching success. Holden and Stalnaker (1975)
reported a further decrease in the numbers of adult bony tail chub in the Green
River in Dinosaur National Monument after the collections by Vanicek et al.
(1970) (i.e., after 1966). This decline also was attributed to the effects of
the dam, particularly the decrease in summer water temperatures.

A pre-impoundment poisoning project in the Green River where Flaming Gorge
Reservoir now is located is often cited as at least a partial cause for the
loss of native fishes immediately downstream of the reservoir. However, a
comparison of fish species present in Dinosaur National Monument before and
after the program (Binns et al. 1963; Vanicek and Kramer 1969; Vanicek et al.
1970) supports the premise that the effect of the poisoning was of a short-
term nature and not responsible for the almost total loss of the bony tail from
that area within a decade.

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