Ph.D. Aquatic Ecology. Utah State University
B.S. Biology. University of Utah
B.A. Economics. Bates College
I am a research fisheries biologist with the U.S. Geological Survey’s Northern Rocky Mountain Science Center and an adjunct faculty in the Ecology Department at Montana State University in Bozeman, MT. I am an applied biologist with goals of providing robust information to inform the management and conservation of aquatic ecosystems. My specific research focuses on improving our understanding of how natural and anthropogenic disturbances influence aquatic ecosystems, the interactions between native and non-native species, and how the life-history patterns and template of aquatic systems will be altered under anticipated changes in global and regional climates. Within this framework my research program consists of a combination of field studies and analytical studies to advance conservation and management and at the same time develop new paradigms in aquatic ecology. My research is built upon a premise of strong collaboration and interaction to facilitate effective research.
Mendenhall Project Title: Forecasting the Effects of Climate Change on the Interactions of Native and Nonnative Salmonids.
Science and Products
Integrated Ecohydrological Science in the Northern Rocky Mountains — the variability of water availability and the effects on ecosystems
Our primary goal is to better understand and characterize how stream environments and the ecosystems they support are influenced by climate change and drought in the Northern Rocky Mountains.
Developing stream temperature networks for the Greater Yellowstone to aid in managing aquatic resources under a changing climate
The topographic diversity and extensive area of protected public land within the Greater Yellowstone demonstrate the importance of this region as a natural resource reserve. Understanding the effects of anticipated changes in climate on aquatic resources and means for managing these resources will ultimately require accurate linkages between empirical data and regional climatic patterns. This...
Improving our understanding of forest-road effects on substrate in headwater streams of the Southwest Crown of the Continent
In 2010, Congress established ten decade-long Collaborative Forest Landscape Restoration Program projects to carry out fuel reduction and ecological restoration treatments on public lands across the country. The Southwest Crown of the Continent was selected as one of the locations under this initiative, given the importance of this region to the economic vitality of local communities and the...
Evaluating the linkages between regional climate patterns, local climate data, and native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) and non-native brook trout (Salvelinus fontinalis) growth, survival, and life-history expressions.
Beyond large-scale climate models, it is becoming increasingly important to quantify how regional climate patterns link with in situ stream temperatures and hydrologic regimes and concomitantly, fish behavior, growth, and survival. Here, we are using comprehensive mark-recapture techniques to evaluate how changing climatic conditions are likely to influence native westslope cutthroat trout and...
Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) is an important cultural and economic resource to the Pyramid Lake Paiute Tribe and a Threatened species under the Endangered Species Act. Here we are integrating the food web information with field estimates of Lahontan cutthroat vital rate and growth information to guide future management and recovery efforts within Pyramid Lake and...
Changes in temperature and precipitation patterns under global climate change are expected to expand the range of suitable habitat for non-natives within stream networks, resulting in significant increases in the distribution and abundance of non-natives. However, our understanding of how landscape attributes can affect local thermal and hydrologic patterns suggests that changes in global...
Evaluating the reintroduction potential and limiting factors associated with anadromous fish reintroductions in the Upper Lewis River, WA
Hydropower facilities on the Lewis River, WA eliminated historic runs of anadromous species to the headwaters of the Lewis River. As anadromous reintroductions are considered and implemented, there remains considerable uncertainty in the viability of reintroductions in reservoir and tributary systems where large populations of non-native species persist and where spawning and rearing habitat...
Development of new information to inform fish passage decisions at the Yale and Merwin hydro projects on the Lewis River, Washington—Final report, 2018
The reintroduction of extirpated salmonids to historically occupied areas is becoming increasingly common as a conservation and recovery strategy. Often, reintroductions are implemented after the factors that originally led to species extirpation have been reduced, eliminated, or mitigated. For anadromous Oncorhynchus spp. (Pacific salmon) and O....Al-Chokhachy, Robert K.; Clark, Christopher L.; Sorel, Mark H.; Beauchamp, David A.
Impacts of nonnative Brown Trout on Yellowstone Cutthroat Trout in a tributary stream
Nonnative trout are a considerable threat to native salmonids, yet our understanding of the mechanisms behind interspecific interactions remains limited. We evaluated the impacts of nonnative Brown Trout Salmo salar on a population of Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri in Montana. We contrasted diets,...Al-Chokhachy, Robert K.; Sepulveda, Adam J.
Status and conservation of Yellowstone cutthroat trout in the Greater Yellowstone Area
No abstract available.Al-Chokhachy, Robert K.; Shepard, Bradley; Burckhardt, Jason; Opitz, Scott; Garren, Dan; Koel, Todd M.; Nelson, Lee M.
Quantifying long-term population growth rates of threatened bull trout: challenges, lessons learned, and opportunities
Temporal symmetry models (TSM) represent advances in the analytical application of mark–recapture data to population status assessments. For a population of char, we employed 10 years of active and passive mark–recapture data to quantify population growth rates using different data sources and analytical approaches. Estimates of adult population...Budy, Phaedra; Bowerman, Tracy; Al-Chokhachy, Robert K.; Conner, Mary; Schaller, Howard
No evidence for ecological segregation protecting native trout from invasive hybridization
We appreciate the comments of Young et al. (2017) on our recent paper (Muhlfeld et al., 2017) concerning spatiotemporal dynamics of hybridization between native westslope cutthroat trout (Oncorhynchus clarkii lewisi; WCT) and introduced coastal rainbow trout (Oncorhynchus mykiss irideus; RBT). Nevertheless, we believe there is no evidence for “...Kovach, Ryan; Muhlfeld, Clint C.; Al-Chokhachy, Robert K.; Amish, Stephen J.; Kershner, Jeffrey L.; Leary, Robb F.; Lowe, Winsor H.; Luikart, Gordon; Matson, Phil; Schmetterling, David; Shepard, Bradley; Westley, Peter A. H.; Whited, Diane; Whiteley, Andrew R.; Allendorf, Fred W.
Evaluating species-specific changes in hydrologic regimes: an iterative approach for salmonids in the Greater Yellowstone Area (USA)
Despite the importance of hydrologic regimes to the phenology, demography, and abundance of fishes such as salmonids, there have been surprisingly few syntheses that holistically assess regional, species-specific trends in hydrologic regimes within a framework of climate change. Here, we consider hydrologic regimes within the Greater Yellowstone...Al-Chokhachy, Robert K.; Sepulveda, Adam J.; Ray, Andrew M.; Thoma, David P.; Tercek, Michael T.
Legacy introductions and climatic variation explain spatiotemporal patterns of invasive hybridization in a native trout
Hybridization between invasive and native species, a significant threat to worldwide biodiversity, is predicted to increase due to climate-induced expansions of invasive species. Long-term research and monitoring are crucial for understanding the ecological and evolutionary processes that modulate the effects of invasive species. Using a large,...Muhlfeld, Clint C.; Kovach, Ryan P.; Al-Chokhachy, Robert K.; Amish, Stephen J.; Kershner, Jeffrey L.; Leary, Robb F.; Lowe, Winsor H.; Luikart, Gordon; Matson, Phil; Schmetterling, David A.; Shepard, Bradley B.; Westley, Peter A. H.; Whited, Diane; Whiteley, Andrew R.; Allendorf, Fred W.
Climate, invasive species and land use drive population dynamics of a cold-water specialist
Climate change is an additional stressor in a complex suite of threats facing freshwater biodiversity, particularly for cold-water fishes. Research addressing the consequences of climate change on cold-water fish has generally focused on temperature limits defining spatial distributions, largely ignoring how climatic variation influences...Kovach, Ryan P.; Al-Chokhachy, Robert K.; Whited, Diane C.; Schmetterling, David A.; Dux, Andrew M; Muhlfeld, Clint C.
Life history characteristics and vital rates of Yellowstone Cutthroat Trout in two headwater basins
The Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri is native to the Rocky Mountains and has declined in abundance and distribution as a result of habitat degradation and introduced salmonid species. Many of its remaining strongholds are in headwater basins with minimal human disturbances. Understanding the life histories, vital rates,...Uthe, Patrick; Al-Chokhachy, Robert K.; Zale, Alexander V.; Shepard, Bradley B.; McMahon, Thomas E.; Stephens, Tracy
Influence of climate drivers on colonization and extinction dynamics of wetland-dependent species
Freshwater wetlands are particularly vulnerable to climate change. Specifically, changes in temperature, precipitation, and evapotranspiration (i.e., climate drivers) are likely to alter flooding regimes of wetlands and affect the vital rates, abundance, and distributions of wetland-dependent species. Amphibians may be among the most climate-...Ray, Andrew M.; Gould, William R.; Hossack, Blake R.; Sepulveda, Adam J.; Thoma, David P.; Patla, Debra A.; Daley, Rob; Al-Chokhachy, Robert K.
Conservation of native Pacific trout diversity in western North America
Pacific trout Oncorhynchus spp. in western North America are strongly valued in ecological, socioeconomic, and cultural views, and have been the subject of substantial research and conservation efforts. Despite this, the understanding of their evolutionary histories, overall diversity, and challenges to their conservation is incomplete. We review...Penaluna, Brooke E.; Abadía-Cardoso, Alicia; Dunham, Jason B.; García de León, Francisco J; Gresswell, Robert E.; Luna, Arturo Ruiz; Taylor, Eric B.; Shepard, Bradley B.; Al-Chokhachy, Robert K.; Muhlfeld, Clint C.; Bestgen, Kevin R.; Rogers, Kevin H.; Escalante, Marco A; Keeley, Ernest R; Temple, Gabriel; Williams, Jack E.; Matthews, Kathleen; Pierce, Ron; Mayden, Richard L.; Kovach, Ryan; Garza, John Carlos; Fausch, Kurt D.
Linkages between unpaved forest roads and streambed sediment: why context matters in directing road restoration
Unpaved forest roads remain a pervasive disturbance on public lands and mitigating sediment from road networks remains a priority for management agencies. Restoring roaded landscapes is becoming increasingly important for many native coldwater fishes that disproportionately rely on public lands for persistence. However, effectively targeting...Al-Chokhachy, Robert K.; Black, Tom A.; Thomas, Cameron; Luce, Charlie H.; Rieman, Bruce; Cissel, Richard; Carlson, Anne; Hendrickson, Shane; Archer, Eric K.; Kershner, Jeffrey L.