February 15-18, 2009 Washington State Convention Center Seattle ...

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MANAGEMENT OF GENETIC DIVERSITY IN PADDLEFISH Polyodon spathula
POPULATIONS AND PROPAGATION
Brian L. Sloss*, Ryan P. Franckowiak, Ed Heist and Robert Klumb
Wisconsin Cooperative Fishery Research Unit
U.S. Geological Survey
College of Natural Resources
University of Wisconsin-Stevens Point
Stevens Point, WI 54481 USA
bsloss@uwsp.edu
The genetic integrity of native populations of paddlefish (Polyodon spathula) can be threatened by propagation through two
primary avenues: the use of genetically divergent source populations as broodstock and the propagation of genetically depauperate
individuals due to insufficient broodstock numbers or crossing/rearing strategies. The basic information necessary to
conduct genetically-sound propagation of paddlefish is to understand the levels and distribution of genetic diversity throughout
the paddlefish’s range and the genetic impact of different crossing and rearing strategies to allow for predictive management of
the genetic diversity of propagated paddlefish. Studies using mitochondrial DNA and microsatellite DNA, although not sufficient
to recognize cohesive stocks of paddlefish, have shown significant genetic structure throughout the paddlefish’s native
range suggesting multiple genetic management units should be enforced.
An example of a genetic assessment prior to wild propagation in one of these units is a series of studies conducted in association
with the upper Missouri River paddlefish propagation. The objectives were twofold: 1) to determine if significant differences
existed among broodsources (Gavins Point tailrace, Niobrara River/Missouri River confluence, and Lake Francis Case/White
River) used in the USFWS’s Missouri River paddlefish propagation conducted at the Gavins Point Dam National Fish Hatchery,
and 2) to determine if male reproductive success significantly deviated from random expectation when a mixed-milt design
(traditional) versus a split-egg lot design (experimental) were used by testing larval fish using genetic paternity analysis. The
number of males used in the three replicate mixed-milt crosses ranged from 4 to 9 whereas the split-lots used 5 males each. All
potential broodsources were genetically similar based on tests of genic differentiation and none deviated from the paddlefish
harvested in a snag fishery located near Gavins Point. Significant male contributions (χ 2 p max -value < 0.0001) were observed
among all traditional crosses with male contribution ranging from 86% to