Rimrock Lake Bull Trout Population Group
The Rimrock Population Group consists of the three bull trout populations that occupy tributaries to Rimrock Lake. Detailed information on each of these can be found here:
These three populations all make use of shared foraging, migration and overwintering (FMO) habitat in Rimrock Lake, and historically would have used downstream habitat in the Tieton and Naches watersheds. Information on conditions, threats and actions for this shared FMO habitat are detailed in the Rimrock Lake FMO page.
Early 90s helicopter rescue of bull trout in shrinking rimrock pool. Transfer to Clear Lake? Find Report.
Population Genetics
The three Rimrock local populations are moderately genetically differentiated from one another (M. P. Small et al., 2009, p. 13). The level of differentiation within Rimrock is high considering the close proximity of the three spawning tributaries, shared usage of Rimrock Lake as FMO habitat, historic lack of barriers between all three tributaries, and present-day lack of barriers between South Fork Tieton River and Indian Creek. These findings have been broadly interpreted to support the conclusion that there is high site fidelity, and correspondingly, low migration between populations and demographic independence. However, metrics of genetic connectivity are easily misinterpreted as indicators of demographic connectivity when population sizes are large or small (Gagnaire et al., 2015, p. 770; Lowe & Allendorf, 2010, p. 3042). Populations can maintain high differentiation despite substantial migration in the case of low effective population size, and while natal site fidelity is high within Rimrock, it is not complete. Small numbers of individuals collected in each of the Rimrock spawning tributaries originate from one of the other Rimrock populations and other individuals demonstrate admixture suggestive of past gene flow among Rimrock populations (M. Small et al., 2011, p. 17; M. P. Small & Martinez, 2011, p. 6).
Shared Threats?