Cooperative Fish and Wildlife Research Units Program: Montana Fishery
Education, Research and Technical Assistance for Managing Our Natural Resources

Montana Fishery Project

Evaluation of the management actions taken in the Lamar River watershed

August 2020 - May 2024


Participating Agencies

  • National Park Service, Yellowstone

Introduction of nonnative fish species has negatively impacted native fishes throughout the United States and the world (Taylor et al. 1984). Yellowstone National Park is not and exception to this unfortunate trend (Koel et al. 2017) with negative effects cascading through the surrounding aquatic and terrestrial food webs (Koel et al. 2017). Beginning in 1889, over 16 million nonnative fish were stocked into Yellowstone's waters; Almost 3 million in the Lamar River watershed (Varley 1981). The Lamar River watershed is considered the most important riverine stronghold for fluvial Yellowstone Cutthroat Trout by the Yellowstone Cutthroat Trout interagency workgroup (NPS, USFS, USGS, States of Montana, Wyoming, Idaho, Utah, and Nevada). Over the decades, introduced Rainbow Trout have continued to migrate further upstream in the Lamar River watershed, displacing and hybridizing with native Yellowstone Cutthroat Trout (Ertel et al. 2017). Numerous mitigation efforts have since been implemented to suppress and curtail the spread of nonnative Rainbow and hybrid trout and protect remaining Yellowstone Cutthroat Trout (and the species ecological function) to pre-invasion conditions (Ertel et al. 2017). However, long-term monitoring and independent data analysis are critical to evaluate the progress of management actions. This proposed Statement of Work and associated budget would fund a thorough analysis of Yellowstone Cutthroat Trout, Rainbow Trout, and hybrid trout response to the institution of a mandatory catch and kill angling regulation coupled with selective mechanical removal of nonnative trout within the watershed. This would be accomplished through a statistical analysis of new and historic fisheries assessment work and creel surveys and interviews of anglers in the watershed.



1. Develop population estimates of Yellowstone Cutthroat, Rainbow, and hybrid trout populations in different regions of the Lamar River watershed.

2. Determine if management actions (selective removal of nonnatives, angling regulations) being undertaken by the NPS are having the desired effect on the native and nonnative fish populations. Are angling regulations being adhered to?

3. Develop management recommendations for achieving NPS management goals in the Lamar River watershed.