7950

• UCREFRP Catalog Number: 7950
• Author: Williams, J. E. and G. R. Wilde
• Title: Taxonomic Status And Morphology Of Isolated Populations Of The White River Springfish,
• USFW Year: 1981
• Copyright Material: YES

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THE SOUTHWESTERN NATURALIST 25(4): 485-503

FEB. 16, 1981

TAXONOMIC STATUS AND MORPHOLOGY OF
ISOLATED POPULATIONS OF THE WHITE RIVER
SPRINGFISH, CRENICHTHYS BAILEYI
(CYPRINODONTIDAE)

JACK E. WILLIAMS' AND GENE R. WILDE
Department of Biological Sciences,
University of Nevada, Las Vegas,
Las Vegas, NV 89154

ABSTRACT. Crenichthys baileyi (Gilbert) is endemic to a series of isolated springs along the
approximately 325 km pluvial White River system of southeastern Nevada. The preference of
Crenichthys for spring habitats and the drying of the pluvial White River have resulted in isolation
of various populations in the remaining spring habitats. Geographic isolation coupled with the
environmental diversity that prevails among the spring habitats caused considerable morphological
divergence among several spring populations. Taxonomic analyses indicate that several populations
are distinct, and are herein described as new subspecies. Five subspecies of the formerly monotypic
C. baileyi are described. One population of C. baileyi has been extirpated and others are endangered
by loss of habitat through introductions of exotic fish species and physical alterations.

Crenichthys baileyi (Gilbert), the White River springfish, inhabits warm springs
throughout the White River system of southeastern Nevada. In pluvial times, this river
system was trioutary to the Colorado River, but is now disjunct except at its most
southerly extent; there, numerous springs provide water for the Moapa River, which
flows into the Colorado River byway of Lake Mead (Blackwelder 1943, Hubbs and Miller
1948a). The pluvial White River is now represented by the White River Valley,
Pahranagat Valley, and the Moapa River. Flows reduced from pluvial times, 10,000 to
30,000 years ago, and the obligatory spring existence of Crenichthys have resulted in
isolation of populations in the remaining suitable spring habitats along the course of the
pluvial White River (Fig. 1) (Hubbs et al. 1974). Robert R. Miller (pers. comm. to R. H.
Reider) suggested that these springs may have been isolated for approximately 10,000
years.
The spring habitats occupied by C. baileyi vary considerably in temperature and
minimum dissolved oxygen values (Table 1). Temperature and minimum oxygen values
are relatively constant within each spring.
The ability of C. baileyi to thrive in springs of high temperature and low oxygen has
been examined by Hubbs and Hettler (1964). They concluded that the high resistance of
certain C. baileyi populations to environmental stress was due to their unique genetic
makeup. The statement that certain populations have become adapted to their own
particular environment implies that some of these populations may be distinct
taxonomic units. This hypothesis is supported by the experiments of Sumner and Sargent
(1940), where they transferred C. baileyi between Mormon Spring (370C and 0.7 ppm
oxygen) and Preston Spring (21 oC and 3.3 ppm oxygen). Of the over 80 fish from Preston

, Present address: Dept. Fisheries and Wildlife, Oregon State Univ., Corvallis, OR 97331.

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