7894

• UCREFRP Catalog Number: 7894
• Author: Loudermilk, W. E. and L. C. Ulmer.
• Title: A Fishery Inventory With Emphasis On Razorback Sucker ‎(
• USFW Year: 1985.
• Copyright Material: NO

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INTRODUCTION
The razorback sucker (Xyrauchen texanus, Abbott) is a native
Colorado River fish currently listed as endangered by the States
s
of California and. Nevada, and is a candidate species for fedF.ral
listing. Because there is no documentation of recruitment in the
upper basin, the Colorado River Fishes Recovery Team has
recommended the razorback sucker be formally classified as
threatened in the upper basin and be evaluated in-1991 for listing
in the lower basin. In 1981, the U.S. Fish and Wildlife Service
(USFWS Region 2) and Arizona Department of Game and Fish entered
into a Memorandum of Understanding to initiate a ten-year stocking
program for razorback suckers in the.Gila, Salt, and Verde rivers
in Arizona. The USFWS (Region 2) agreed not to pursue federal
listing until the success?of the reintroduction program could be
evaluated in 1991.
The continued decline of the razorback sucker has concerned
scientists since the early 1950's (Behnke 1980 Behnke and Benson
1980; Deacon 1968; Dill 1944; Gustafson 1975; Holden and Stalnaker
1975; Mamika 1979; McAda and Wydoski 1980; Miller 1961; Miller et
al. 1982; Minckley and Deacon 1968; Minckley and Kobetich 1973;.
Moffett 1942; Wydoski et al. 1980). The general reasons cited for.
this decline include dams and other riverine modifications which
have altered the historical, chemical, physical and biological
nature of the River. Exotic fish intro4uctions are believed to
have also contributed to an increase in mortality due'to predation
on various razorback sucker life stages.