9383

• UCREFRP Catalog Number: 9383
• Author: SWCA, I.
• Title: Recovery Goals for the four Colorado River Endangered Fish Species.
• USFW Year: 2000.
• USFW - Doc Type: Logan.
• Copyright Material: NO

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1.0. INTRODUCTION

'ackground
The U.S. Fish and Wildlife Service (Service), under Section 4(c) of the Endangered
Species Act of 1973, as amended (ESA; 16 U.S.C. 1531 et. seq.), is required to conduct a review
of the status of threatened species and endangered species every 5 years for consideration of
reclassification. Four species of fishes indigenous to the Colorado River Basin are listed as
"endangered" under the ESA, and currently warrant review for possible reclassification. These
are the Colorado pi ow (Ptychocheilus lucius), humpback chub (Gila cypha), razorback
sucker (Xyrauchef! ), and bonytail (Gila elegans).
The Colorado pikeminnow and the humpback chub were first included on the List of
Endangered Species issued by the Office of Endangered Species on March 11, 1967 (32 FR
4001). They were considered "endangered" as provided for by the Endangered Species
Conservation Act of 1969 (16 U.S.C. 668aa), and listed as "endangered" under Section 4(c)(3)
of the Endangered Species Act of 1973. e razorback sucker and bonytail were listed under
final rules published on October 23, 19, FR 54957), and April 23, 1980 (45 FR 27710),
respectively. Recovery plans for Col01ado pI eminnow, humpback chub, razorback sucker, and
bonytail were approved August 6, 1991(USFWS 1991); September 19, 1990 (USFWS 1990a);
December 23, 1998 (USFWS 1998); and September 4, 1990 (USFWS 1990b), respectively.
Critical habitat for all four species was designated March 21, 1994 (59 FR 13374).
Listing ofthe four Colorado River endangered fishes preceded the policy by the Service
in 1996 to clarify the concept of a distinct population segmen S; 61 FR 4722-4725), and the
concept ofDPS was not applied at the time that these species "ere listed. Two or more DPSs
may be considered at the time of reclassification (i.e., downlisting) for each of the four species.
Three elements are considered in the decision to designate DPSs; discreteness, significance, and
conservation status (see Appendix A).
The four species are members of a unique assemblage of fishes native to the Colorado
River Basin consisting of 35 species with 74% level of endemism (Miller 1959). ~
assemblage of the Colorado River is threatened by large mainstem dams and small d~sions,
degraded water quality, habitat modification, and nonnative fish species (Miller 1961; Mincldey

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