7948

• UCREFRP Catalog Number: 7948
• Author: Martinez, A. M.
• Title: Observed Fin Ray Deformities Resulting from Handling Stress in the Intensive Culture of Razorback Suckers.
• USFW Year: 1995.
• USFW - Doc Type: \
• Copyright Material: NO

Anita M. Martinez
3
The razorback sucker (Xyrauchen texanus), an endemic Colorado River catostomid,
is in danger of extinction due to habitat loss (Carlson and Muth 1989.; Tyus and Karp 1989;
Tyus and Karp 1990; Osmundson and Kaeding 1991), possible competition and predation
by non-native species (Minckley 1983; Marsh-and Brooks 1989; Bestgen 1990), and lack
of recruitment (Tyus 1987; Papoulias 1988; Lanigan and Tyus 1989; Tyus. and Karp 1990).
Hybridization between native, sympatric catostomid species may also be contributing to
the demise of this monotypic genus (Buth and Murphy 1984; Buth et al. 1987; Tyus and
Karp 1990) although this theory has been questioned (Minckley et al. 1991). The
razorback sucker is listed as endangered by the Endangered Species Act of 1973 and is
protected by state statutes in Arizona, California, Colorado, Nevada, New Mexico, Utah,
and Wyoming. A cooperative agreement between the Colorado Division of Wildlife
(CDOW) and U.S. Fish and Wildlife Service in 1993 and 1994 initiated hatchery
production at the CDOW Fish Research Hatchery (FRH) to establish a refugia and a
source of razorback suckers for possible augmentation of wild populations.
Razorback suckers have been reared extensively in earthen ponds containing
plankton and other natural foods (Hamman 1987) and in isolated backwaters of Lake
Mohave (Mueller et al. 1993). Tyus and Severson (1990) examined growth and survival
of intensively cultured larvae age 5 to 45 days fed five commercial fry diets. These
perFormance investiga#ions were continued up to age 126 days by Severson et al. (1992).
Though a recommended diet (Tyus and Severson 1990; Severson et al. 1992) was fed to
razorback sucker larvae reared at the FRH in 1993, approximately 65% of the larvae