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Fisheries Applied Research and Technical Assistance

 

Helena Field Office

 

Population genetics of bull trout in Warm Springs Creek, upper Clark Fork River, Montana

 

Bull trout in Warm Springs Creek, Montana

Bull trout in Warm Springs Creek, Montana

Twin Lakes Creek, tributary to Warm Springs Creek

Twin Lakes Creek, tributary to Warm Springs Creek

The Clark Fork River system west of the Continental Divide in Montana historically contained one of the largest metapopulations of bull trout (Salvelinus confluentus) throughout the species range.  Warm Springs Creek contains the most-upstream population of Federally-threatened bull trout in the Clark Fork River system.  Since the early 1900s bull trout habitat within the Warm Springs Creek drainage has been extensively fragmented by water development and associated control structures resulting in isolation of bull trout populations in Twin Lakes and Storm Lake Creeks (Figure 1).  Bull trout from Storm Lake and Twin Lakes Creeks may also be entrained into Silver Lake, a reservoir which receives water diverted from those two streams.  Presence of nonnative brook trout, which can both compete and hybridize with bull trout, may represent an additional threat to bull trout in the Warm Springs drainage.

Warm Springs Creek drainage in western Montana, USA

Figure 1.  Warm Springs Creek drainage in western Montana, USA.  In 2008, bull trout tissue samples were collected in Storm Lake Creek, Twin Lakes Creek, upper and lower Twin Lakes, Barker Creek, Foster Creek, Warm Springs Creek, and Silver Lake. Myers Dam is a barrier to upstream passage by fishes.  Diversion structures on Storm Lake Creek and Twin Lakes Creek (upstream from the aqueduct effectively isolate these habitats from the mainstem Warm Springs Creek.  Map by Dan Brewer, USFWS.

The US Fish and Wildlife Service’s 2002 Draft Bull Trout Recovery Plan identifies the collection of genetic data as a priority for recovery planning in many watersheds, but no baseline genetic data were available for bull trout populations in the Warm Springs Creek drainage. Given this, we used genetic makers (microsatellite DNA) to: (a) characterize genetic diversity both within and among remnant bull trout populations in the Warm Springs Creek drainage; and (b) use genetic population assignment techniques to assign individuals of unknown origin entrained in Silver Lake to their most likely population of origin.

In 2008 we collected tissue samples (finclips) from bull trout in various locations in the watershed (Figure 1).  Genetic analyses were conducted by the Conservation Genetics Lab at the US Fish and Wildlife Service’s Abernathy Fish Technology Center, in Washington state.  The data show low levels of genetic variation for bull trout within different tributaries of Warm Springs Creek, likely as a result of population isolation; small effective population sizes; and restricted gene flow among populations (DeHaan et al. 2009).  Silver Lake entrains bull trout from Storm Lake Creek, and bull trout ´ brook trout hybrids were detected in Warm Springs Creek, upper and lower Twin Lakes, and in Silver Lake.  

Project report:  DeHaan, P., L. Godfrey, D. Peterson, and D. Brewer.  2009. Bull trout population genetic structure and entrainment in Warm Springs Creek, Montana. Abernathy Fish Technology Center, US Fish and Wildlife Service, Abernathy, WA. (download report)

Revised Project Report*: DeHaan, P., L. Godfrey, D. Peterson, and D. Brewer.  2010. Bull trout population genetic structure and entrainment in Warm Springs Creek, Montana. Abernathy Fish Technology Center, US Fish and Wildlife Service, Abernathy, WA. (dowload report)

* Note: The revised report includes data from a sub-population of bull trout in the West Fork Warm Springs Creek, and summarizes information on occurrence first generation hybrids between bull trout X brook trout.

Funding:  NorthWestern Energy

Collaborators:  Pat DeHaan and Linda Godfrey, Abernathy Fish Technology Center – US Fish and Wildlife Service; Dr. Doug Peterson (USFWS); Dan Brewer (USFWS); Montana Fish, Wildlife and Parks; USDA Forest Service; and USDA Natural Resources Conservation Service

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Updated 12/13/10