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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Alteration of flow and temperature regimes associated with the closure of Glen
Canyon Dam (Lake Powell) also is implicated as a factor in the loss of
bony tail chub populations there; bony tail chub were fairly common in Lake
Powell immediately after closure, but declined soon afterward (Utah State
Department of Fish and Game 1964, 1969).

Introductions of nonnative fishes probably also have contributed to decline of
the bony tail chub. Tyuset al. (1982b) reported that rivers of the Upper
Basin have been colonized in recent times by at least 42 nonnative fish
species. Kaeding et al. (1986) suggested that the synergistic effect of
increases in nonnative fishes and altered flow/temperature regimes adversely
impacted the bony tail chub. Valdez et al. (1982) suggested that loss of
habitat for Gila species in the Upper Basin could result in severe
interspecific competition.

The apparent ability of bony tail chubs to hybridize with the roundtail and
humpback chubs under hatchery conditions also may be a factor in the decline
of the bony tail chub (Stalnaker and Holden 1973). The very small number of
bony tail chub remaining in the Colorado River basin increases the likelihood
of hybridization with more abundant species of Gila.

In summary, habitat alteration caused by dams, water depletions from
irrigation, interactions with nonnative fishes, and hybridization with other
Gila have been suggested as the major factors in the decline of the bony tail
chub in the Colorado River basin.

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