Year of Award

2011

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Chair

Fred W. Allendorf

Committee Co-chair

Robb F. Leary

Commitee Members

Lisa A. Eby

Keywords

conservation genetics, hybridization, sauger, walleye

Publisher

University of Montana

Abstract

Hybridization with non-native walleye may play a substantial role in sauger declines throughout the upper Missouri River drainage of Montana and Wyoming. I identified 11 microsatellite loci to detect interspecific hybridization and describe the genetic population structure of sauger. Two major population groupings of sauger were revealed by principal component analysis. The first consisted of samples from the Missouri and lower Yellowstone River drainages, which showed no evidence for genetic divergence among each other. The second major grouping contained samples from the Bighorn River drainage and the upper Yellowstone River. Samples from the upper Bighorn River drainage were genetically distinct from downstream samples. The Bighorn and upper Yellowstone River samples had substantially lower heterozygosity and allelic richness than the lower Yellowstone and Missouri River samples. Analysis of simulated data sets suggested that 100% of sauger and walleye and 100% of first and second generation hybrids could be correctly identified using these 11 loci. This indicates that my analysis method has the power to discriminate sauger and walleye and to detect hybridization and introgression. I detected only eighteen hybrids out of 925 individuals analyzed. Hybridization appeared recent, as nearly 50% of the hybrids showed significant evidence for having a non-hybrid ancestor within two generations. Only one hybrid was detected in the Missouri River. All others were found in the Yellowstone River drainage, despite a substantially higher rate of walleye stocking in the Missouri River drainage. Environmental conditions in the Yellowstone River drainage may be more conducive to hybridization, or hybrid and walleye survival. The rarity of hybrids, despite massive walleye stocking, is unexpected. Introgression of walleye genes into native sauger does not appear to be an immediate threat. Nevertheless, the presence of hybrids could still be harmful because their production represents wasted reproductive effort. Given my results, I recommend that (1) the transfer of genetically distinct stocks of sauger not take place; (2) historical levels of gene flow among populations be restored; and (3) the walleye fishery in the upper Missouri River drainage be replaced with a sauger or sterile walleye fishery.

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© Copyright 2011 Daniel Michael Bingham