The Effects of Long-term Hatchery Releases on Snake River Basin
Steelhead Populations
Melanie M. Paquin
NOAA/ Northwest Fisheries Science Center, Seattle, WA 98112
Poster Abstract:
Pacific Coast Steelhead Management Meeting
Boise, Idaho
March 4-6, 2008
This study compares the genetic variation among two groups of Snake River
Basin steelhead populations: those with little or no hatchery influence (wild), and
those with varying levels of influence from hatchery fish (naturally-produced).
Wild and naturally-produced populations were used to test the hypothesis that
introgression by steelhead hatchery fish has altered the naturally occurring
genetic variation among Snake River Basin steelhead populations. Fifty-one
steelhead populations from throughout three Snake River sub-basins, the Lower
Snake, Clearwater, and Salmon Rivers, were analyzed. Analysis of 14
microsatellite loci was used to estimate levels of gene flow and to identify
geographic areas that contain genetically differentiated populations. Regression
analyses were performed between genetic and geographic distance using
fixation index (FST) pairwise comparisons and river Km distance. These analyses
show overall genetic variation is low within the Lower Snake River Sub-basin
relative to the other two sub-basins. More importantly, patterns of genetic
variation between the two population categories, wild and naturally-produced,
within sub-basins were similar. This suggests that hatchery introgression,
especially from non-indigenous hatchery sources, has not dramatically influenced
the genetic structure of the Snake River steelhead populations. The results
reported here are consistent with recent studies of reproductive success in
hatchery-origin steelhead that suggest that non-indigenous or highly
domesticated stocks may have relatively little success reproducing in the wild.