8072

• UCREFRP Catalog Number: 8072
• Author: Burke, T. and G. Mueller.
• Title: Native Fish Work Group 1992 Annual Report.
• USFW Year: 1993.
• USFW - Doc Type: \
• Copyright Material: NO

INTRODUCTION
The razorback sucker, Xyrauchen texanus, is an endangered fish
endemic to the Colorado River basin. The largest remaining
population of this unique species occupies Lake Mohave, a
mainstream Colorado River reservoir in Arizona and Nevada, where it
has been studied since impoundment of the lake in the 1950s
(Minckley 1983, Minckley et al. 1991). The adult population,
estimated to number about 60,000 fish (Marsh 1992), is comprised of
old individuals (McCarthy and Minckley 1987). Although these
reproduce annually and produce abundant larvae, the latter
disappear before attaining juvenile size and there has been no
detectable recruitment in nearly four decades (Minckley 1983,
Minckley et al. 1991). Available evidence suggests that predation
by non-native species on early life stages is among the factors
responsible for this recruitment failure (Marsh and Langhorst
1988). Because of its size and extraordinary genetic diversity
(Dowling and Minckley, in press), the Lake Mohave razorback sucker
population is a focal point for recovery of this critically
imperiled species, and attempts to prevent its extirpation-are
vital to survival of the taxon.
Augmentation is considered a viable management alternative toward
perpetuation of razorback sucker in Lake Mohave. Although
successful propagation and rearing techniques have been developed
(Inslee 1982, Hamman 1987), stocking elsewhere of young fish