7741

• UCREFRP Catalog Number: 7741
• Author: Burdick, B. D.
• Title: A Plan to Evaluate Stocking to Augment or Restore Razorback Sucker in the Upper Colorado River - Final.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

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A PLAN TO EVALUATE STOCKING TO
AUGMENT OR RESTORE RAZORBACK SUCKER
IN THE UPPER COLORADO RIVER
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INTRODUCTION
Distribution, Abundance, and Status
The razorback sucker (Xyrauchen texanus) is one of several native fishes
that was formerly common and widespread throughout warmwater reaches of the
Colorado River Basin, primarily in the mainstem and large tributaries from
0 Wyoming to Mexico. However, its current range has been reduced by about 75%
(Seethaler 1978; McAda and Wydoski 1980; Bestgen 1990). Razorback sucker
numbers have declined appreciably since human alteration of the aquatic
environment began in the basin near the turn of this century. The continuing
decline of their numbers and apparent unsuccessful recruitment has forced the
razorback sucker closer toward extinction in nature. Because of its
0 precarious position, the U. S. Fish and Wildlife Service (USFWS) listed the
razorback sucker as an endangered species (effective 22 November 1991; Federal
Register, Vol. 56, No. 205, 23 October 1991) under authority of the Endangered
Species Act of 1973 (USFWS 1973). A recovery plan for this species has not
yet been developed. The razorback sucker is presently also protected by the
states of Arizona, California, Colorado, Nevada, and Utah.
Most investigators (e. g., Tyus 1987 et al.; Osmundson and Kaeding 1989a)
consider the razorback sucker to be more rare than the Colorado squawfish
(Ptychocheilus lucius). Although reproduction has been documented in the
Green River (Tyus et al. 1987) in the upper basin and continues in Lake Mohave
in the lower basin (Marsh and Minckley 1989) no juveniles have been captured.
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