NMFS NUMBER: 96-SWR-004
Diversity in California Steelhead Oncorhynchus mykiss)
L. Nielsen, Monique C. Fountain, Vicky Kirby, and Dennis
Marine Fisheries Service, Southwest Region, 501 West Ocean
Boulevard, Suite 4200, Long Beach, California 90802-4213.
TELEPHONE: (562) 980-4033
genetic diversity was revealed for Oregon and California
steelhead populations using 10 microsatellite loci. Fishers
exact tests for population independence supported strong
genetic substructure in sample populations at the southern
extent of this species range. Population genetic structure
depicted with these loci strongly supports biogeographic
structure in coastal steelhead throughout California and
reveals significant separation of Oregon and California
populations into distinct evolutionary units. Two tests
of isolation-by-distance support clear biogeographic structure
in California steelhead populations and southern steelhead
hatchery stocks retain genetic similarity to their original
parental stocks in the Sacramento River. Differentiation
of Sacramento River and San Joaquin River populations
was , however, not possible using these 10 loci. AMOVA
analysis of the genetic diversity found at these ten loci
showed that 88.8% of the diversity was within populations.
Only 8.5% of the allelic diversity was found among populations,
and 2.7% was found among large geographic regions. Altogether
the results indicated that these microsatellite loci are
valuable tools for addressing fine scale population genetic
questions at the basin level, for differentiation of wild
stocks, or looking at hatchery vs. wild interactions.
More loci are needed, however, to answer questions of
life history differences between rainbow trout at the
southern most reaches of their range.