9698

• UCREFRP Catalog Number: 9698
• Author: Borley, K., and M.M. White.
• Title: Mitochondrial DNA variation in the endangered Colorado pikeminnow
• USFW Year: 2006.
• USFW - Doc Type: a comparison among hatchery stocks and historic specimens.
• Copyright Material: YES

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918

BORLEY AND WHITE

FIGURE I.-Colorado pikeminnow collection locations in
the Colorado River basin: (1) Yampa River (74YC stock); (2)
Green River (81 YC, in part); (3) Colorado River (81 YC, in
part); (4) Colorado River (91YC); (5) Colorado River; (6) San
Iuan River; and (7) White River. Approximate sample
locations of the museum specimens are indicated by acronyms
for the collecting institutions: Brigham Young University
(BYU), California Academy of Science (CAS), Kansas
University (KU), Tulane University (TV), and University of
New Mexico (UNM) (see Table 2 for additional details).

Discussion

Our results are consistent with the presence of a
single Colorado pikeminnow ESU within the Colorado
River basin. Widespread interbasin transfers of hatch-
ery-reared fish (Morizot et al. 2002) would tend to
homogenize allele and haplotype frequencies across the
drainage. Our data for the Colorado pikemirmow also
suggest a genetic bottleneck. Several issues probably

contributed to the limited haplotype variation observed
in Colorado pikeminnow. First, the hatchery brood-
stocks were founded with a very small number of
females (Morizot et al. 2002), and genetic diversity is
known to rapidly decline in captive populations when
the number of breeding adults is small (Vrijenhoek
1996). Second, the Colorado pikemirmow has under-
gone a precipitous decline in population size and range
(Osmundson and Burnham 1998); this decline would
have resulted in loss of genetic variation.
Our survey of museum specimens suggests that low
levels of variation predate the population decline and
stocking history of the Colorado pikeminnow in the
1900s. The Colorado River may have been subjected to
a severe drought approximately 7,500 years ago
(Tarboton 1995). Such long-term drought is thought
to have significantly impacted fish faunas, whose
recovery may take decades or centuries (Matthews
1998). As part of an evaluation of the hypothesis that
such drought events would have long-term impacts on
genetic variation, Douglas et al. (2003) concluded that
the patterns of variation observed in the flarmelmouth
sucker Catostomus latipinnis, another Colorado River
endemic, were consistent with such a drought scenario.
Their data supported occirrrence of a rapid population
expansion after a bottleneck at the end of the
Pleistocene. The same drought that affected the
flannelmouth sucker may have impacted genetic
variation in Colorado pikeminnow and other Colorado
River endemics. Garrigan et al. (2002) attributed low
levels of mtDNA variation in bony tails Gila elegans to
population bottlenecking but found no evidence of
such bottlenecking in humpback chub G. cypha or
razorback suckers Xyrauchen texanus.
Low-frequency alleles are the most prone to genetic
drift in a bottleneck (Nei et al. 1975). Previous
allozyme studies of wild Colorado pikeminnow found
rare basin-specific alleles (Ammerman and Morizot

TAB
and N
pikemi
mainta
Center

Primer

ArgBL
ND4L1
ND4L1
NAP2(

1989;
found
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basin -:
hatche
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stock
obtaim
rado) E
preseni
Lo'h
minno'
such Vi
mtDNl
captive
inheritl
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mtDNf
populal
mtDNl
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present
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2002).
(Morizt
with fj
persona

TABLE 2.-Sample number, collection information, and haplotype for the museum samples of Colorado pikeminnow
sequenced and then compared with three year-classes maintained at Dexter National Fish Hatchery and Technology Center, New
Mexico. Included with the museum samples were those from Brigham Young University (BYU), California Academy of
Sciences (CAS), Kansas University (KU), Tulane University (TV), and University of New Mexico (UNM).

Sample # Museum # River Location State Year Haplotype
BYU2 25282 Green Emery County Utah 1934 A
BYU3 176314 Green Daggett County Utah 1964 A
BYU4 176315 Green Daggett County Utah 1964 A
CAS2 SU 3833 Colorado Yuma Arizona 1890 A
CAS4 SU 33212 Colorado San Bernardino California 1938 A
KUI 5445-1 Green Uintah County Utah 1959 A
KU2 5445-2 Green Uintah County Utah 1959 A
TU2 108940 Green Jensen Utah 1976 A
TU3 108940 Green Jensen Utah 1976 A
UNM767 767 San Juan Navajo Dam to Colorado New Mexico 1961 A
UNM3234 3234 San Juan Rio Arriba New Mexico 1959 A

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Yampa,
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(Green I
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