Abstract:
The Jarbidge River in Idaho and Nevada represents the southern-most habitat occupied
by bull trout across the species range. Bull trout in the Jarbidge River have been isolated
from other populations for over 100 years due to the construction of multiple impassable
dams and several kilometers of unsuitable habitat. Given its unique geographic location
and isolated nature, the conservation of bull trout populations in the Jarbidge River is a
high priority. Although genetic data has been recognized as an important factor for
guiding bull trout recovery planning in the Jarbidge River system, previously genetic
information related to Jarbidge bull trout populations was limited. Our objective in this
study was to provide a fine-scale analysis of genetic variation within and among Jarbidge
bull trout populations. We used a suite of 15 microsatellite loci to characterize genetic
variation within and among six tributaries in the Jarbidge River that contain bull trout.
Estimates of genetic variation within these six populations including allelic richness and
expected and observed heterozygosity tended to be lower than those we had observed for
other populations across the species range. Estimates of effective population size were
less than 50 individuals for all six of the tributary populations. Estimates of variation
among populations indicated that each tributary contains a genetically distinct spawning
population. The greatest level of variation we observed was between tributaries in the
East and West Fork. We observed greater levels of gene flow among West Fork Jarbidge
tributaries than we did among East Fork tributaries and little evidence for gene flow
between the East and West Fork Jarbidge. Genetic population assignments suggest that
individuals migrate among tributaries within the East and West Fork and to a lesser
extent between the two forks.
