8101

• UCREFRP Catalog Number: 8101
• Author: Lentsch, L. D., Y. Converse, P. D. Thompson, D. T. A. Crowl and D. C. A. Toline.
• Title: Bonytail Reintroduction Plan for the Upper Colorado River Basin - Final Report.
• USFW Year: 1996.
• USFW - Doc Type: Salt Lake City, Utah.
• Copyright Material: NO

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Reintroduction Issues
Hybridization
For successful reintroduction of bonytail into the UCRB, potential
hybridization with humpback chub and roundtail chub must be addressed.
Evidence exists that hybridization takes place to some degree in the wild
between these closely related congeners.
Vanicek and Kramer (1969) caught bonytail and roundtail chub in the same
areas but never in the same gill net. They suggest that spatial, not
temporal, mechanisms separate bonytail from other Gila species. Kaeding et
al. (1990) also believe that the isolating mechanism is spatial based on their
sampling protocol and study design. However, Kaeding et al. (1990) did find
ripe roundtail chub and humpback chub in the same net. Hamman (1982) was able
to artificially produce viable offspring from bonytail X roundtail chub and
bonytail X humpback chub crosses, however, these crosses did not occur
naturally in a hatchery environment. Therefore, ethological mechanisms may
separate spatially and temporally spawning overlap in the Gila complex
(Kaeding et al. 1990).
Viable hybridization of the Gila complex has also been demonstrated in
hatcheries and through genetic investigations (Hamman 1982; Dowling and
DeMarais 1993). Intergrade or hybrid individuals in the wild offer
morphological evidence for natural hybridization (Holden and Stalnaker 1970;
Douglas et al. 1989). Hybridization may be a result of the breakdown of the
integrity of the naturally evolved system (Valdez and Clemmer 1982), or
hybridization may be a natural phenomenon of speciation and biogeography
(Dowling and DeMarais 1993). Human activity, which has resulted in rapid
declines in the number of reproductively active individuals for all Gila
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