Boaters fly fishing on the Missouri River in Montana
Clint Muhlfeld, Ph.D.
I am a Research Aquatic Ecologist at the USGS Northern Rocky Mountain Science Center (NOROCK) in West Glacier, Montana. I currently serve as the Acting Center Director of NOROCK in Bozeman, Montana.
Research interests
As a Research Aquatic Ecologist, I study the ecology, evolution, and conservation of freshwater species and ecosystems. My research examines how climate variability, hydrologic change, biological invasions, and habitat alteration influence freshwater biodiversity and ecosystem processes, with particular expertise in cold-water biota. I have led ecological and evolutionary studies across freshwater systems ranging from glacier-fed mountain streams and large river networks to lakes, as well as regional and global assessments of trout and char. My research combines long-term ecological studies, field research, genetics, and quantitative modeling and draws on multiple disciplines, including ecology, fisheries science, genetics, and hydrology.
Science and Products
Filter Total Items: 24
USGS Northern Rocky Mountain Science Center Fiscal Year 2025 Highlights
The USGS Northern Rocky Mountain Science Center (NOROCK) proudly supports Federal, State, Tribal, and other partners by delivering high-quality data, cutting-edge science, and practical tools to support natural resource management. Below are some of NOROCK’s highlights during fiscal year 2025.
Building drought early warning systems for fisheries and water management across the U.S.
As droughts become more frequent and severe, freshwater ecosystems and the valuable fisheries they support face increasing challenges. These impacts can lead to declines in fish populations, threatening biodiversity, recreational fishing, and economies. To address these threats, scientists at the USGS Northern Rocky Mountain Science Center and Montana State University are developing Drought Early...
Leveraging Existing Data to Assess the Vulnerability of Native Salmonid Populations in the Greater Yellowstone Area
Project Overview: Native Yellowstone cutthroat trout and mountain whitefish in the Greater Yellowstone Ecosystem (GYA) are ecologically and socio-economically important species, but are threatened by drought, rising water temperatures, habitat loss, and non-native species. Researchers supported by this North Central CASC project will use climate data and extensive population records to...
Climate change links fate of glaciers and rare alpine stream invertebrates in Glacier National Park
The extensive loss of glaciers in Glacier National Park (GNP) is iconic of the global impacts of climate warming in mountain ecosystems. However, little is known about how climate change may threaten alpine stream species, especially invertebrates, persisting below disappearing snow and ice masses in GNP. Two alpine stream invertebrates – the meltwater stonefly and the glacier stonefly – are...
Assessing the Vulnerability of Native Trout in the Northern Rockies: Linking Science and Management for Climate Adaptation
Trout are one of the most culturally, economically, and ecologically important groups of freshwater fishes in the Rocky Mountain region. However, human impacts and climate change are significantly altering freshwater ecosystems that support native trout species. Despite their broad importance, many of the region’s trout populations are threatened and some require immediate conservation...
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.
Experimental suppression of invasive lake trout: Implications for conservation of imperiled bull trout in Glacier National Park
After 14,000 years of dominance, Glacier National Park’s (GNP) greatest native aquatic predator is at high risk of extirpation (local extinction) in several lakes on the western slopes of the Continental Divide. The decline of threatened bull trout in GNP is directly attributed to the invasion and establishment of nonnative lake trout, which consistently displace bull trout in systems where lake...
Predicting Climate-Induced Expansions of Invasive Fish in the Pacific Northwest: Implications for Climate Adaptation of Native Salmon and Trout
The headwaters of the Columbia River Basin in the Northern Rocky Mountains region is widely recognized as a stronghold for native fish, containing some of the last remaining connected cold-water habitats for species such as the threatened bull trout and native westslope cutthroat trout. However, as temperatures rise, non-native invasive fish species could be poised to prosper in the...
Understanding Climate Impacts on Native and Invasive Fish for Conservation, Management, and Economic Goals in the Northern Rockies
As the origin of three major basins that drain the Columbia, Missouri, and Saskatchewan rivers, Montana is the hydrologic apex for North America. The Northern Rocky Mountain region is home to some of the last remaining interconnected habitats for many native fishes, including the threatened bull trout and native westslope cutthroat trout. The Northern Rockies are also experiencing...
Science in Glacier National Park
Glacier National Park (GNP) is considered a stronghold for a large diversity of plant and animal species and harbors some of the last remaining populations of threatened and endangered species such as grizzly bear and bull trout, as well as non threatened, yet ecologically important species such as bighorn sheep and black bear. The mountain ecosystems of GNP that support these species are dynamic...
Western Waters Invasive Species and Disease Research Program
Researchers at the Northern Rocky Mountain Science Center's Western Waters Invasive Species and Disease Research Program work extensively with federal, state, tribal, regional, and local partners to deliver science to improve early detection and prevention of invasive species and disease; understand complex interactions that promote invasive species and disease, and their impacts (and associated...
Climate Change Impacts on Invasive Species in the Northwest: A Synthesis and Path Forward
Invasive species have increasingly severe consequences for ecosystems and human communities alike. The ecological impacts of invasive species are often irreversible, and include the loss of native species and the spread of disease. Implications for human communities include damaged water transportation systems, reduced crop yields, reduced forage quality for livestock, and widespread...
Montana trout fishing
Boaters fly fishing on the Missouri River in Montana
Trout fishing in Montana
Fly fishing for trout in one on Montana's rivers.
Fly fishing for trout in one on Montana's rivers.
Aquatic insect sampling in Glacier National Park
Researchers taking aquatic insect samples in a high-elevation Glacier National Park stream as part of ecohydrological monitoring efforts to study the effects of climate change on aquatic species and ecosystems.
Researchers taking aquatic insect samples in a high-elevation Glacier National Park stream as part of ecohydrological monitoring efforts to study the effects of climate change on aquatic species and ecosystems.
What a catch!
Angler holding a brown trout caught from a Montana River
Angler holding a brown trout caught from a Montana River
Spawning Westslope Cutthroat Trout in the Flathead
Spawning Westslope Cutthroat Trout in the FlatheadThis is spawning westslope cutthroat trout captured in Langford Creek, North Fork Flathead River, Montana.
Spawning Westslope Cutthroat Trout in the Flathead
Spawning Westslope Cutthroat Trout in the FlatheadThis is spawning westslope cutthroat trout captured in Langford Creek, North Fork Flathead River, Montana.
Science and Products
Filter Total Items: 24
USGS Northern Rocky Mountain Science Center Fiscal Year 2025 Highlights
The USGS Northern Rocky Mountain Science Center (NOROCK) proudly supports Federal, State, Tribal, and other partners by delivering high-quality data, cutting-edge science, and practical tools to support natural resource management. Below are some of NOROCK’s highlights during fiscal year 2025.
Building drought early warning systems for fisheries and water management across the U.S.
As droughts become more frequent and severe, freshwater ecosystems and the valuable fisheries they support face increasing challenges. These impacts can lead to declines in fish populations, threatening biodiversity, recreational fishing, and economies. To address these threats, scientists at the USGS Northern Rocky Mountain Science Center and Montana State University are developing Drought Early...
Leveraging Existing Data to Assess the Vulnerability of Native Salmonid Populations in the Greater Yellowstone Area
Project Overview: Native Yellowstone cutthroat trout and mountain whitefish in the Greater Yellowstone Ecosystem (GYA) are ecologically and socio-economically important species, but are threatened by drought, rising water temperatures, habitat loss, and non-native species. Researchers supported by this North Central CASC project will use climate data and extensive population records to...
Climate change links fate of glaciers and rare alpine stream invertebrates in Glacier National Park
The extensive loss of glaciers in Glacier National Park (GNP) is iconic of the global impacts of climate warming in mountain ecosystems. However, little is known about how climate change may threaten alpine stream species, especially invertebrates, persisting below disappearing snow and ice masses in GNP. Two alpine stream invertebrates – the meltwater stonefly and the glacier stonefly – are...
Assessing the Vulnerability of Native Trout in the Northern Rockies: Linking Science and Management for Climate Adaptation
Trout are one of the most culturally, economically, and ecologically important groups of freshwater fishes in the Rocky Mountain region. However, human impacts and climate change are significantly altering freshwater ecosystems that support native trout species. Despite their broad importance, many of the region’s trout populations are threatened and some require immediate conservation...
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.
Experimental suppression of invasive lake trout: Implications for conservation of imperiled bull trout in Glacier National Park
After 14,000 years of dominance, Glacier National Park’s (GNP) greatest native aquatic predator is at high risk of extirpation (local extinction) in several lakes on the western slopes of the Continental Divide. The decline of threatened bull trout in GNP is directly attributed to the invasion and establishment of nonnative lake trout, which consistently displace bull trout in systems where lake...
Predicting Climate-Induced Expansions of Invasive Fish in the Pacific Northwest: Implications for Climate Adaptation of Native Salmon and Trout
The headwaters of the Columbia River Basin in the Northern Rocky Mountains region is widely recognized as a stronghold for native fish, containing some of the last remaining connected cold-water habitats for species such as the threatened bull trout and native westslope cutthroat trout. However, as temperatures rise, non-native invasive fish species could be poised to prosper in the...
Understanding Climate Impacts on Native and Invasive Fish for Conservation, Management, and Economic Goals in the Northern Rockies
As the origin of three major basins that drain the Columbia, Missouri, and Saskatchewan rivers, Montana is the hydrologic apex for North America. The Northern Rocky Mountain region is home to some of the last remaining interconnected habitats for many native fishes, including the threatened bull trout and native westslope cutthroat trout. The Northern Rockies are also experiencing...
Science in Glacier National Park
Glacier National Park (GNP) is considered a stronghold for a large diversity of plant and animal species and harbors some of the last remaining populations of threatened and endangered species such as grizzly bear and bull trout, as well as non threatened, yet ecologically important species such as bighorn sheep and black bear. The mountain ecosystems of GNP that support these species are dynamic...
Western Waters Invasive Species and Disease Research Program
Researchers at the Northern Rocky Mountain Science Center's Western Waters Invasive Species and Disease Research Program work extensively with federal, state, tribal, regional, and local partners to deliver science to improve early detection and prevention of invasive species and disease; understand complex interactions that promote invasive species and disease, and their impacts (and associated...
Climate Change Impacts on Invasive Species in the Northwest: A Synthesis and Path Forward
Invasive species have increasingly severe consequences for ecosystems and human communities alike. The ecological impacts of invasive species are often irreversible, and include the loss of native species and the spread of disease. Implications for human communities include damaged water transportation systems, reduced crop yields, reduced forage quality for livestock, and widespread...
Montana trout fishing
Boaters fly fishing on the Missouri River in Montana
Boaters fly fishing on the Missouri River in Montana
Trout fishing in Montana
Fly fishing for trout in one on Montana's rivers.
Fly fishing for trout in one on Montana's rivers.
Aquatic insect sampling in Glacier National Park
Researchers taking aquatic insect samples in a high-elevation Glacier National Park stream as part of ecohydrological monitoring efforts to study the effects of climate change on aquatic species and ecosystems.
Researchers taking aquatic insect samples in a high-elevation Glacier National Park stream as part of ecohydrological monitoring efforts to study the effects of climate change on aquatic species and ecosystems.
What a catch!
Angler holding a brown trout caught from a Montana River
Angler holding a brown trout caught from a Montana River
Spawning Westslope Cutthroat Trout in the Flathead
Spawning Westslope Cutthroat Trout in the FlatheadThis is spawning westslope cutthroat trout captured in Langford Creek, North Fork Flathead River, Montana.
Spawning Westslope Cutthroat Trout in the Flathead
Spawning Westslope Cutthroat Trout in the FlatheadThis is spawning westslope cutthroat trout captured in Langford Creek, North Fork Flathead River, Montana.