9411

• UCREFRP Catalog Number: 9411
• Author: Williamson, J. H., D. C. Morizot and G. J. Carmichael.
• Title: Biochemical Genetics of Endangered Colorado Pikeminoow from the Green, Yampa, Colorado, and San Juan Rivers.
• USFW Year: 1998.
• USFW - Doc Type: \
• Copyright Material: NO

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' Conclusions
Our analyses of allozyme variability in Colorado pikeminnow population samples will be presented
' pursuant to five major areas of interest: 1) allelic variability in wild adult Colorado pikeminnow; 2) allelic
variability in juvenile and YOY Colorado pikeminnow individuals; 3) allelic variability in captive hatchery
Colorado pikeminnow populations; 4) genetic management implications in development of hatchery
' populations and use of hatchery fish for reintroduction into natural populations; and 5) implications of
allele frequency estimates in wild and captive Colorado pikeminnow populations for genetic management.
Allozyme variability in wild adults. No clustering of alleles within river basins was apparent,
meaning that alleles were more or less evenly dispersed throughout collection sites. Even with very small
sample size (most likely reflecting scarcity of pikeminnow in the river), the San Juan River sample appears
to have lost genetic diversity, probably through genetic drift accompanying population bottlenecks and
reductions in immigration. The lack of observed genetic differentiation is consistent with hypotheses of
panmixia, but does not exclude the possibility of past differentiation maintained by behavioral isolation but
now precluded by habitat disturbance or anthropogenic barriers. Also, stocking of Colorado pikeminnow
for more than 16 years may have masked any differentiation that existed. Colorado pikeminnow were
stocked into the White River and Colorado River systems with fish produced from Yampa River fish and
into the San Juan River using fish produced from mixed Colorado/Green River broodfish (see Appendix 1;
Table 1).
Allozyme variability in juveniles. Juvenile Colorado pikeminnow could be wild individuals or
reintroduced young Colorado pikeminnow from hatchery stocking in the early to mid 1980s. Allele
frequency data are insufficient to support either hypothesis with certainty.
Allozyme variability in young-of-the-year. While a few individual allele frequency comparisons
approach statistical significance, the vast majority of alleles exhibited a conspicuous lack of geographic
differentiation. Six alleles at frequencies < 0. 10 were found in both Colorado River and Green River
samples; the three basin-restricted alleles all were found at frequencies < 0.01. As in the study of
Ammerman and Morizot (1989), an overall lack of genetic differentiation within and between river basins
is apparent.
Genetic variability in hatchery populations. Ammerman and Morizot (1989) concluded that the
Colorado-Green River DX-F,(81) and Yampa River DX-F2(87) populations reflected allele frequencies
estimated from wild YOY samples; expansion of sampling in this study suggests that founder effects may
have significantly increased and decreased frequencies of the GPI-I*A and ES2*b alleles, respectively,
relative to wild populations. Of the five apparently basin-specific alleles identified to date (GR *b, TPI-I
*a, and TPI-2*a in the Green River and GPI-2 *c and PEPS*B in the Colorado River), only GR*b was
detected in the adult broodfish sampled here. Analysis of the Yampa River DX-F2(91) captive population
' sample proved noteworthy in that six additional polymorphic loci were observed. Liver samples permitted
resolution of LDH-3 and BGAL, both shown to be polymorphic by Ammerman and Morizot (1989).
Newly identified polymorphisms of as yet unknown geographic differentiation were detected at GPDj,
AIEp-1, aGLU-2, and ACP-1, with less common alleles ranging from 0.02 - 0.25.
Implications of allele frequency estimates.- The new polymorphic loci and alleles identified in the
present study compel a reevaluation of the suitability of current hatchery populations maintained as refugia
for future reintroduction. The discovery of several rare alleles that may be liver-specific indicates a need
for full characterization and monitoring of hatchery populations to insure maintenance of genetic
variability. Geographic distributions of uncommon alleles further suggest that hatchery populations be
' derived from Colorado River and Green River and/or Yampa River individuals, rather than the currently
available populations from mixed Colorado River and Green River individuals segregated from a Yampa