Determination of the Origin of Bull Trout below Cabinet Gorge Dam
Lukas P. Neraas and Paul Spruell
Wild Trout and Salmon Genetics Lab, University of Montana, Missoula, MT 59812
ABSTRACT --Migratory bull trout (Salvelinus confluentus) that
spawned in the Clark Fork River drainage historically inhabited Lake Pend
Oreille as subadult and adult fish. If
this premise is correct, the construction of Cabinet Gorge Dam disrupted the
connectivity of the Pend Oreille / Clark Fork metapopulation.
We used eight microsatellite loci to compare bull trout collected at the
base of Cabinet Gorge Dam to fish sampled both above and below the dam. These
data were analyzed using Cavalli-Sforza and Edwards' (CSE) chord distance and
Paetkau’s individual assignment test. The
CSE UPGMA and Paetkau’s individual assignment test suggest that Cabinet Gorge
bull trout are genetically more similar to tributaries sampled from above the
dam. This relationship suggests that the risks associated with
passing a limited number of radio tagged adults are minimal compared to the
potential genetic and demographic benefits to populations located above the dam.
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