Little Kern Golden Trout (Oncorhynchus mykiss whitei)

For more information contact Molly Stephens: mrstephens@ucdavis.edu

Background and Significance of Study

The Little Kern golden trout (LKGT) is one of two golden trout subspecies designated as the California State fish. Both golden trout subspecies were endemic to the Kern River watershed prior to European settlement, with the Little Kern form restricted to the Little Kern River above a natural barrier (Evans et al. 1973). Extensive stocking of non-native rainbow trout in the basin during the first half of this century led to the near extinction of the LKGT due to hybridization. Planting of non-native trout ceased in the 1950’s, and the California Department of Fish and Game (CDFG) began surveys in 1965 to initiate restoration efforts. Allozyme electrophoretic analyses begun in 1976 at UC Davis ultimately identified six pure populations of GT-LK occupying only ten miles of stream out of the 100 miles of historic range (Gall and May 1997 and references therein). The Little Kern golden trout was federally listed as a Threatened species under the Endangered Species Act in 1978.

Restoration efforts began in 1975 with the first rotenone treatment by the California Department of Fish and Game. In addition to chemical treatments, restoration measures have included restocking of treated waters with pure LKGT, construction of barriers to the upstream movement of non-native trout, habitat improvement of streams damaged by cattle grazing, public education, and continued monitoring of fish populations, their genetic integrity, and habitat conditions. Although restoration was believed complete in 1996, subsequent genetic analyses identified a number of streams and lakes within the system that had been stocked with one strain of LKGT that contained hybridized trout.

The purpose our research is to identify hybridized populations of GT-LK and quantify levels of introgression with rainbow trout using microsatellite and newly developed SNP markers. This information will be used in the management and conservation of the species.

Little kern golden trout map image

Figure 1. Distribution of Little Kern golden trout broodstock during restoration efforts. (From Gall 1997).

Materials and Methods

  • 28 populations (5 reference Little Kern broodstock, 5 hatchery and wild rainbow trout)
  • 18 O. mykiss microsatellite loci
  • 10 SNP loci

Results

Comparative analysis of SNP and microsatellite data reveal similar estimates of location and levels of rainbow trout introgression (Figure 2). A manuscript detailing results of comparative analysis is in preparation (Stephens et al., in prep).

Little kern golden trout graph of rainbow trout introgression

Figure 2. STRUCTURE Bayesian analysis of Little Kern golden trout SPN data. Populations 1-5 are Little Kern broodstock populations, populations 6-23 and 25 are LKGT populations, and 26-30 are hatchery and wild rainbow trout. Each vertical bar represents an individual fish, with individuals grouped by population number (as in Table 4) on the x-axis. Bar colors represent golden trout (red) and rainbow trout (green), with the proportion of green indicating of the level of rainbow trout introgression in a given individual.

Collaborators

California Department of Fish and Game (CDFG)

U.S. Forest Service (USFS)

Funding is provided by the CDFG and the US Fish and Wildlife Service