7984

• UCREFRP Catalog Number: 7984
• Author: Maddux, H. R., L. A. Fitzpatrick and W. R. Noonan.
• Title: Colorado River Endangered Fishes Critical Habitat - Draft, Biological Support Document.
• USFW Year: 1993.
• USFW - Doc Type: Salt Lake City, Utah.
• Copyright Material: NO

Table 1 (continued).
COMMON NAME
SCIENTIFIC NAME
Family Cyprinodontidae
Moapa/White River springfish Crenichthys baileyi
Railroad Valley springfish Crenichthys nevadae
Desert pupfish Cyprinodon macularius
Monkey Springs pupfish Cyprinodon sp.
Family Poeciliidae
Gila topminnow
Family Cottidae
Mottled sculpin
Paiute sculpin
Family Mugilidae
Striped mullet
Poeciliopsis occidentalis
Cottus bairdi
Cottus beldingi
Mugil cephalus
Changes to the aquatic resources of the Basin has had a profound effect on the native fish
fauna. Several species and subspecies are extinct, including the Las Vegas dace, Pahranagat
spinedace and Monkey Springs pupfish. Of the remaining species, 44 percent are federally
listed as endangered or threatened and an additional 28 percent identified as candidates to the
Federal lists. Only 20 percent of the native fish fauna has not been identified as potentially
in need of protection under the Act. The Basin States also have acknowledged the need to
protect the native fish species. Over 70 percent of the native species are on State lists of
special status species.
Historically, the native fish fauna of the mainstream Colorado River was dominated by native
minnows (cyprinids) and suckers (catostomids) (Minckley et al. 1986). However, four of
these, the razorback sucker, Colorado squawfish, humpback chub, and bonytail, are now
federally listed as endangered species. These fishes are threatened with extinction due to the
combined effects of habitat loss (including regulation of natural flow, temperature, and
sediment regimes); proliferation of introduced fishes; and other man-induced disturbances
(Miller 1961; Minckley 1973; Carlson and Muth 1989; Minckley and Douglas 1991).
Colorado squawfish populations only in the Upper Basin, where their numbers are relatively
high only in the Green River basin of Utah and Colorado (Tyus 1991a). Razorback sucker
and bonytail chub stocks consist predominately of old adult fish, and they remain only
because of the longevity inherent in these species (USFWS 1990a; Minckley et al. 1991).
6