Cooperative Research Units
Education, Research And Technical Assistance For Managing Our Natural Resources
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Assess the recovery of westslope cutthroat trout and Arctic ...


September 2017 - June 2021


Native populations of Westslope Cutthroat Trout Oncorhynchus clarkii lewisi and Arctic Grayling Thymallus arcticus in Yellowstone National Park were reduced or eliminated through competition, predation, and hybridization with nonnative fishes that were historically stocked by managers, ostensibly to enhance sportfishing. National Park Service (NPS) fisheries managers carried out conservation actions aimed at restoring Westslope Cutthroat Trout (WCT) and Arctic Grayling populations in two watersheds in Yellowstone National Park, including East Fork Specimen Creek in the Gallatin River drainage and Grayling Creek in the Madison River drainage. Conservation actions included 1) building barriers impassable to upstream fish movement to isolate watersheds; 2) applying rotenone, a lethal fish toxicant, to eliminate all fish from the watersheds above the barriers; and 3) reintroducing native fish to the isolated watersheds.

NPS fisheries managers plan to continue restoration efforts of WCT and Arctic Grayling in additional park watersheds, but first want to understand how past conservation efforts performed to guide future restoration actions. Therefore, the goal of this research project is to assess the recovery and status of the reintroduced populations of WCT and Arctic Grayling in East Fork Specimen and Grayling creeks. Our specific objectives are to 1) assess population abundance, size structure, condition, individual growth, and reproductive success of WCT and Arctic Grayling; 2) determine the spatial distributions of restored WCT and Arctic Grayling in relation to the reintroduction sites; 3) determine how population size structure and condition of recovering WCT in East Fork Specimen Creek compare to those of the hybridized WCT population they replaced; and 4) estimate the genetic population structure of recovering Westslope Cutthroat Trout relative to the contributions of the various WCT donor sources (Last Chance, Geode, and Muskrat creeks, and Sun Ranch Hatchery). Attainment of these objectives will provide NPS fisheries managers with information needed to better manage these populations and to guide future restoration efforts elsewhere in the Park.


Current Staff

Federal Staff: 101

Masters Students: 239

Phd Students: 154

Post Docs: 55

University Staff: 241

5 Year Summary

Students graduated: 695

Scientific Publications: 1962

Presentations: 4417



Funding Agencies

  • Yellowstone National Park


Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey