I am a USGS emeritus research biologist and affiliate assistant professor in the Department of Ecology at Montana State University. My research is focused on the factors that influence fish abundance, distribution, and life history within, and among watersheds, and how these relationships change in through time.
Research Interests: My interest in the role of disturbance in shaping the aquatic systems has led to research on the interactions among landscape-scale environmental features, instream habitat characteristics, and cutthroat trout abundance and distribution. Currently my research is focused on the effects of fire, timber harvest, invasive species, and climate change on persistence of native trout in the Intermountain West. I have been involved with the lake trout issue in Yellowstone Lake since these invaders were first discovered in 1994 and act as chair of the lake trout suppression independent scientific review panel that was formed 2008.
- Ph.D. Fisheries Science. 1994. Oregon State University
- M.S. Wildlife Science. 1973. Utah State University
- B.S. Biology. 1970. University of New Mexico
Professional societies/affiliations/committees/editorial boards
Honors, awards, recognition, elected offices
Scientific/Oral Presentations, Abstracts
Science and Products
FAQ on Invasive Lake Trout in Yellowstone Lake
Predicting Effects of Climate Change on Native Fishes in Northern Great Plains Streams
Estimating Future Streamflow in Eastern Montana Using the Precipitation-Runoff Modeling System and the RegCM3 Regional Climate Model
Yellowstone Lake Acoustic Biotelemetry Project Home Page
Bob Gresswell's Past Projects
Understanding Extreme Climate Events in the North Central U.S.
The Potential Influence of Changing Climate on the Persistence of Native Salmonids
Fish response to successive clearcuts in a second-growth forest from the central Coast range of Oregon
Invasive Lake Trout reproduction in Yellowstone Lake under an active suppression program
Carbon dioxide-induced mortality of four species of North American fishes
Yellowstone Lake ecosystem restoration: A case study for invasive fish management
A call for global action to conserve native trout in the 21st century and beyond
Revealing migration and reproductive habitat of invasive fish under an active population suppression program
Rapid early development and feeding benefits an invasive population of lake trout
The effectiveness of non-native fish removal techniques in freshwater ecosystems: a systematic review
Application of multistate modeling to estimate salmonid survival and movement in relation to spatial and temporal variation in metal exposure in a large mining-impacted river
A portfolio framework for prioritizing conservation efforts for Yellowstone Cutthroat Trout populations
Fish response to contemporary timber harvest practices in a second-growth forest from the central Coast Range of Oregon
Using carbon dioxide in fisheries and aquatic invasive species management
Science and Products
FAQ on Invasive Lake Trout in Yellowstone LakeThese Frequently Asked Questions and responses were developed by USGS and their partners with the Lake Trout Suppression Scientific Review Panel *. The purpose of these FAQs is to provide answers to several of the more common questions concerning the lake trout suppression program in Yellowstone Lake, within Yellowstone National Park, and provide information about the current status of the program...
Predicting Effects of Climate Change on Native Fishes in Northern Great Plains StreamsThe Northern Great Plains of North America are a region of profound global importance because organisms that live in these semi-arid prairie environments have developed a unique ability to live through conditions of extreme heat, cold, floods, and drought. Prairie streams are essential components of these ecosystems because they provide critical “green lines” of habitat for both aquatic and...
Estimating Future Streamflow in Eastern Montana Using the Precipitation-Runoff Modeling System and the RegCM3 Regional Climate ModelStreams in the Northern Great Plains provide critical “green lines” of habitat for aquatic and terrestrial wildlife. However, changes in water quantity associated with global climate change may transform some prairie streams from essential refuges to habitats no longer capable of supporting fishes. Although studies have examined climate change effects on larger river basins across the United...
Yellowstone Lake Acoustic Biotelemetry Project Home PageFishery biologists and managers are increasingly consumed with the recovery and restoration of native trout and salmon throughout the western United States. These fish historically inhabited a variety of freshwater habitats, but have declined due to habitat degradation, fragmentation and introduction of nonnative species. Introduced fishes constitute a major threat to the persistence of native...
Bob Gresswell's Past ProjectsBob Gresswell's Past Projects
Understanding Extreme Climate Events in the North Central U.S.The climate of the North Central U.S. is driven by a combination of factors, including atmospheric circulation patterns, the region’s complex topography which extends from the High Rockies to the Great Plains, and variations in hydrology. Together, these factors determine the sustainability of the region’s ecosystems and the services that they provide communities. In order to understand the vuln
The Potential Influence of Changing Climate on the Persistence of Native SalmonidsUnderstanding how climate change will influence habitat for interior species of native salmonids is critical for effective management and recovery of these species. The US Department of the Interior, the US Department of Agriculture, state fisheries managers, and non-governmental organizations are increasingly challenged in attempting the recovery and restoration of native trout and salmon through
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Fish response to successive clearcuts in a second-growth forest from the central Coast range of OregonResearch dating back to the 1950 s has documented negative effects from harvesting of primeval forests on stream ecosystems of the Pacific Northwest. By the early 1990 s, state and federal forest practice rules governing timber harvest were modified throughout North America to better protect aquatic habitats and biotic resources, principally salmonids. These rules inspired a generation of studies
Invasive Lake Trout reproduction in Yellowstone Lake under an active suppression programIn Yellowstone Lake, predation by invasive Lake Trout Salvelinus namaycush has caused significant abundance declines in native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri. Lake Trout suppression has been ongoing since 1995; assessment and simulation modeling are used to measure suppression effectiveness and guide efforts. Lake Trout reproduction demographics are linked to these model
Carbon dioxide-induced mortality of four species of North American fishesFisheries managers have a growing interest in the use of carbon dioxide (CO2) as a tool for controlling invasive fishes. However, limited published data exist on susceptibility of many commonly encountered species to elevated CO2 concentrations. Our objective was to estimate the 24-h 50% lethal concentration (LC50) and 95% lethal concentration (LC95) of CO2 for four fishes (Rainbow Trout Oncorhync
Yellowstone Lake ecosystem restoration: A case study for invasive fish managementInvasive predatory lake trout Salvelinus namaycush were discovered in Yellowstone Lake in 1994 and caused a precipitous decrease in abundance of native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri. Suppression efforts (primarily gillnetting) initiated in 1995 did not curtail lake trout population growth or lakewide expansion. An adaptive management strategy was developed in 2010 that
A call for global action to conserve native trout in the 21st century and beyondTrout and char (hereafter, trout ) represent some of the more culturally, economically and ecologically important taxa of freshwater fishes worldwide (Kershner, Williams, Gresswell, & Lobón‐Cerviá, 2019a). Native to all continents in the Northern Hemisphere (as well as western Mediterranean Africa), trout belong to seven genera (Oncorhynchus , Salvelinus, Salmo , Hucho, Parahucho, Brachymystax and
Revealing migration and reproductive habitat of invasive fish under an active population suppression programEndemic species face a variety of threats including predation from non‐native invaders. In some cases, however, invasive species can be managed by directly suppressing populations, and tracking technologies that allow researchers to identify movement patterns and aggregations representative of the population can facilitate suppression activities. In Yellowstone Lake (Yellowstone National Park, Wyo
Rapid early development and feeding benefits an invasive population of lake troutLake trout (Salvelinus namaycush) were discovered in Yellowstone Lake in 1994 and their population expanded dramatically despite intensive suppression. The lake is species-depauperate, with no major lake trout embryo predators. We hypothesized that without this predation threat, lake trout free embryo feeding and growth may be greater than in their native range, leading to increased survival of ag
The effectiveness of non-native fish removal techniques in freshwater ecosystems: a systematic reviewIn aquatic systems, biological invasions can result in adverse ecological effects. Management techniques available for non-native fish removal programs (including eradication and population size control) vary widely, but include chemicals, harvest regimes, physical removal, or biological control. For management agencies, deciding on what non-native fish removal program to use has been challenging
Application of multistate modeling to estimate salmonid survival and movement in relation to spatial and temporal variation in metal exposure in a large mining-impacted riverWe used telemetry and multistate modeling to estimate survival and movement of brown trout Salmo trutta and westslope cutthroat trout Oncorhynchus clarkii lewisi in relation to dissolved copper concentrations in 189 km of the upper Clark Fork River, Montana, a mining-impacted river in western Montana. Annual survival estimates for both brown trout (range, 0.27-0.53) and westslope cutthroat trout
A portfolio framework for prioritizing conservation efforts for Yellowstone Cutthroat Trout populationsManaging and conserving native taxa are becoming increasingly challenging because of mounting threats and limited resources, predicating the need for frameworks to prioritize conservation actions. We integrated attributes of population persistence, genetic status, threats from nonnative species, and threats from climatic shifts to prioritize conservation actions for Yellowstone Cutthroat Trout Onc
Fish response to contemporary timber harvest practices in a second-growth forest from the central Coast Range of OregonWe used a paired-watershed approach to investigate the effects of contemporary logging practices on headwater populations of coastal cutthroat trout (Oncorhynchus clarkii clarkii) and juvenile coho salmon (Oncorhynchus kisutch) in a second-growth Douglas-fir forested catchment in Oregon. Stream habitat and fish population characteristics, including biomass, abundance, growth, size, and movement, w
Using carbon dioxide in fisheries and aquatic invasive species managementTo restore native fish populations, fisheries programs often depend on active removal of aquatic invasive species. Chemical removal can be an effective method of eliminating aquatic invasive species, but chemicals can induce mortality in nontarget organisms and persist in the environment. Carbon dioxide (CO2) is an emerging alternative to traditional chemical control agents because it has been dem