7315

• UCREFRP Catalog Number: 7315
• Author: Colorado Water Conservation Board.
• Title: State of Colorado Hatchery Feasibility Study for Endangered Fishes of the Colorado River Basin, Vols. 1 & 2.
• USFW Year: 1993.
• USFW - Doc Type: \
• Copyright Material: NO

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REFERENCE NUMBER:

CITATION:

026

Bulb, D.G., R. W. Murphy, and L. Ulmer. 1987. Population
differentiation and introgressive hybridization of the tlannelmouth
sucker and of hatchery and native stocks of the razorback sucker.
Transactions of the American FISheries Society. 116(1):103-110.

SPECIES AND LIFE STAGE:

TOPICS:

KEYWORDS:

RZ. RZ_ADU, RZ_JUV

Research

RAZORBACK SUGKER. GENETICS, INTROGRESSIVE
HYBRIDIZATION, FLANNELMOUTH SUCKER,
ELECTROPHORESIS

SUMMARY: A problem regarding the management of any fish species that is artificially mass-produced
concerns the maintenance of the natural gene pooL Sampling error results in the enhancement
of the frequencies of some alleles and the reduction of others in the necessarily small
subsample of the wild population. This inherent characteristic of hatchery propagation coupled
with the razorback's tendency to hybridize naturally with other catostomids is cause for concern
when considering hatchery augmentation of natural populations.

Flannelmouth specimens for this study were obtained from the Virgin River in Arizona, the
mouth of the Paria River in AZ. the Little Colorado river drainage, AZ. Upper Colorado
River near Grand Junction, CO. Razorback specimens were obtained from Lake Mohave, AZ,
Senator Wash Reservoir, CA, and form Dexter national FISh Hatchery, NM. Brain, liver,
heart, and skeletal muscle tissues were used for electrophoresis. Gene prodUCts compared
included acid phosphatase, alcohol dehydrogenase, creatine kinase, glycerol-3-phosphate
dehydrogenase and several others.

Flannelmouth sucker were polymorphic in 9 of 21 loci in at least one of the geographic
locations. Within each of these locations, genotype arrays were within Hardy-Weinberg
expectations of genetic variability. Between the different geographic locations, statistically
sigJIifi~t structuring of gene flow patterns exisL Indicating geographic limitations of certain
polymorphism, though no complete allelic difference. Razorback sucker were polymorphic in
11 out of 21 loci in at least one of the geographic locations. Within each of these sample
populations genotype arra-ys were within Hardy-Weinberg expectations except for the Dexter
National FISh Hatchery population which shOWed excessive gene restriction in one loci.
Between the different geographic locations no structuring of gene flow patterns was noted.
Four loci were identified that were species-specific and could be used as marker loci. Two of
these four loci have allelic distributions suggesting some gene flow between the two species.
Both alleles are present in both species and the predominant allele in each species is present
in low frequency in the other species. Gene flow is proceeding both from tlannelmouth to
razorback sucker and from razorback to flannelmouth sucker. There is the possibility that both .
alleles at both loci were present in a. common ancestor of the catostomids. Evidence of
introgression in tlannelmouth sucker is found in the Virgin River sample and the upper
Colorado River sample. Introgression is apparently rare enough for the species to maintain
integrity of their respective gene pools in the wild. The current hatchery stock at Dexter has
not been appreciably affected by sampling error in favor of introgressed genes form
flanneJmouth suckers, and has fewer introgressed genes than parental stock from Lake Mohave.
As long as breeding stock continues to be obtained form natural populations, the breeding
program for razorback suckers at Dexter can be quite successful Programs that select
subsequent breeding stock from their own reared stock are ill advised for the razorback.

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