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James J Roberts, PhD

James Roberts is a Research Ecologist based out of Sandusky, OH.

James has broad research expertise and investigates the ecological consequences of environmental stressors like climate change and eutrohpication for aquatic systems and specifically fish populations. Currently, he is investigating the potential effects climate change may have on the persistance of Colorado River cutthroat trout (Oncorhynchus clarkii pleuriticus) in stream and lake habitats throughout the Upper Colorado River basin. He has also conducted research in the Laurentian Great Lakes examining the ecological consequences of seasonal hypolimnetic hypoxia, dead zones, in Lake Erie. Specifically, he investigated the effects (behavioral, physiological,and inter-specific) of hypoxia on the benthic fish assemblage of Lake Erie, while focusing on yellow perch. 

Science and Products

link
A cutthroat trout up close. James Roberts photo. USGS.

Climate Change and Trout

Cold-water fishes like trout, salmon, and charr are especially vulnerable to shifting conditions related to climate change; for example, warmer temperatures and more variable hydroclimate. Native cutthroat trout of the southern Rocky Mountains now only occupy a tiny fraction of their historic habitats because of stressors such as non-native fishes, habitat fragmentation, and detrimental land...
By
Ecosystems, Fisheries Program, Fort Collins Science Center
link

Climate Change and Trout

Cold-water fishes like trout, salmon, and charr are especially vulnerable to shifting conditions related to climate change; for example, warmer temperatures and more variable hydroclimate. Native cutthroat trout of the southern Rocky Mountains now only occupy a tiny fraction of their historic habitats because of stressors such as non-native fishes, habitat fragmentation, and detrimental land...
Learn More
link
Cover image SIR 2017-5162

Characterization of Water Quality and Biology in the Fountain Creek Watershed

Monument and Fountain Creeks and their respective watersheds, located in the Front Range of Colorado, serve as important drainages for surface runoff, waste-water treatment operations, and as a water supply for downstream agricultural needs. As population growth continues in these watersheds, more and more pressures are being applied to the receiving streams, especially Fountain Creek.
By
Colorado Water Science Center
link

Characterization of Water Quality and Biology in the Fountain Creek Watershed

Monument and Fountain Creeks and their respective watersheds, located in the Front Range of Colorado, serve as important drainages for surface runoff, waste-water treatment operations, and as a water supply for downstream agricultural needs. As population growth continues in these watersheds, more and more pressures are being applied to the receiving streams, especially Fountain Creek.
Learn More
link
A cutthroat trout up close. James Roberts photo. USGS.

Ecological Responses to Fish Reclamation Treatments

Piscicides have been used in Rocky Mountain stream and lakes to restore native fish populations. In the last two decades concerns over piscicide effects to non-target organisms, primarily aquatic invertebrates, has increased. Although piscicides have been used for more than 70 years the impact to invertebrate assemblages has not been well studied and is largely unknown. Given the importance a...
By
Ecosystems, Water Resources, Environments Program, Fisheries Program, Fort Collins Science Center
link

Ecological Responses to Fish Reclamation Treatments

Piscicides have been used in Rocky Mountain stream and lakes to restore native fish populations. In the last two decades concerns over piscicide effects to non-target organisms, primarily aquatic invertebrates, has increased. Although piscicides have been used for more than 70 years the impact to invertebrate assemblages has not been well studied and is largely unknown. Given the importance a...
Learn More
link
Scientists work on insect traps in the Prairie Pothole region of North Dakota.

Aquatic Ecology and Contaminants

The Aquatic Ecology and Contaminants Team investigates critical ecological processes operating in aquatic and riparian ecosystems and how these processes are affected by human activities. We address questions through a combination of field studies, laboratory experiments, and modeling, while working at multiple levels of biological organization from cells through ecosystems. Topics include land...
By
Fort Collins Science Center
link

Aquatic Ecology and Contaminants

The Aquatic Ecology and Contaminants Team investigates critical ecological processes operating in aquatic and riparian ecosystems and how these processes are affected by human activities. We address questions through a combination of field studies, laboratory experiments, and modeling, while working at multiple levels of biological organization from cells through ecosystems. Topics include land...
Learn More
link
Native westslope cutthroat trout swim in the north fork of the Flathead River in northwestern Montana.

The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
By
Climate Adaptation Science Centers, Climate Adaptation Science Center
link

The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
Learn More
link
Native westslope cutthroat trout swim in the north fork of the Flathead River in northwestern Montana.

The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
By
Climate Adaptation Science Centers, Climate Adaptation Science Center
link

The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
Learn More

Dataset for temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river

The trace element selenium is an essential element with a narrow window between concentrations needed to support life and those that cause toxicity to egg laying organisms. Selenium bioaccumulation in aquatic organisms is primarily the result of trophic transfer through food webs and is poorly predicted by dissolved concentrations in freshwater bodies. To better understand the hydrologic and biolo
By
Wyoming-Montana Water Science Center

Invertebrate community data from native trout lakes and streams in the Southern Rocky Mountains

Native trout in the West suffer a high degree of vulnerability, as highlighted by cutthroat trout, a group of 14 subspecies, most of which have been petitioned for listing under the Endangered Species Act (ESA). In the Southern Rocky Mountains, greenback cutthroat trout (Oncorhynchus clarkii stomias; GBCT) are listed as threatened under the ESA, and few populations remain, in part because of the i
By
Colorado Water Science Center

Multimetric Index macroinvertebrate values from the Fountain Creek Basin, Colorado 2005 to 2016.

These data have been collected as part of a cooperative project in between the U.S. Geological Survey Colorado Water Science Center, Colorado Springs Utility, and Colorado Springs Engineering. This project began in 2005 and has collected macroinvertebrate samples from Fountain Creek and its tributaries to monitor the biological condition of this watershed. Provided in this data release are Multime
By
Fort Collins Science Center

Datasets of ecological communities (invertebrates and fish), streamflow, habitat, and water quality to examine the presence of trends in ecological communities from the Fountain Creek basin, Colorado, USA, 2003-2016.

These data were used for an analysis as part of a long-term project monitoring the biological communities, habitat, and water quality of the Fountain Creek Basin. Biology, habitat, and water quality data have been collected at 10 sites starting in 2003. These data include annual samples of aquatic invertebrate communities, fish communities, water quality, and quantitative riverine habitat collecte
By
Colorado Water Science Center
Filter Total Items: 18

The past as prelude to the future for understanding 21st-century climate effects on Rocky Mountain Trout

Bioclimatic models predict large reductions in native trout across the Rocky Mountains in the 21st century but lack details about how changes will occur. Through five case histories across the region, we explore how a changing climate has been affecting streams and the potential consequences for trout. Monitoring records show trends in temperature and hydrographs consistent with a warming climate
By
Ecosystems, Northern Rocky Mountain Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geology, Geophysics, and Geochemistry Science Center

Fragmentation and thermal risks from climate change interact to affect persistence of native trout in the Colorado River basin

Impending changes in climate will interact with other stressors to threaten aquatic ecosystems and their biota. Native Colorado River cutthroat trout (CRCT; Oncorhynchus clarkii pleuriticus) are now relegated to 309 isolated high-elevation (>1700 m) headwater stream fragments in the Upper Colorado River Basin, owing to past nonnative trout invasions and habitat loss. Predicted changes in climat

Assessing and addressing the re-eutrophication of Lake Erie: central basin hypoxia

Relieving phosphorus loading is a key management tool for controlling Lake Erie eutrophication. During the 1960s and 1970s, increased phosphorus inputs degraded water quality and reduced central basin hypolimnetic oxygen levels which, in turn, eliminated thermal habitat vital to cold-water organisms and contributed to the extirpation of important benthic macroinvertebrate prey species for fishes.
By
Ecosystems, Great Lakes Science Center

Effects of hypoxia on consumption, growth, and RNA:DNA ratios of young Yellow Perch

As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species

Seasonal and interannual effects of hypoxia on fish habitat quality in central Lake Erie

1. Hypoxia occurs seasonally in many stratified coastal marine and freshwater ecosystems when bottom dissolved oxygen (DO) concentrations are depleted below 2–3 mg O2 L-1. 2. We evaluated the effects of hypoxia on fish habitat quality in the central basin of Lake Erie from 1987 to 2005, using bioenergetic growth rate potential (GRP) as a proxy for habitat quality. We compared the effect of hypoxi

Thermal regimes of Rocky Mountain lakes warm with climate change

Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess th
By
Water Resources, Climate Research and Development Program, Land Change Science Program, Colorado Water Science Center

Effects of internal phosphorus loadings and food-web structure on the recovery of a deep lake from eutrophication

We used monitoring data from Lake Lugano (Switzerland and Italy) to assess key ecosystem responses to three decades of nutrient management (1983–2014). We investigated whether reductions in external phosphorus loadings (Lext) caused declines in lake phosphorus concentrations (P) and phytoplankton biomass (Chl a), as assumed by the predictive models that underpinned the management plan. Additionall
By
Water Resources, Colorado Water Science Center

Nonnative trout invasions combined with climate change threaten persistence of isolated cutthroat trout populations in the southern Rocky Mountains

Effective conservation of Cutthroat Trout Oncorhynchus clarkii lineages native to the Rocky Mountains will require estimating effects of multiple stressors and directing management toward the most important ones. Recent analyses have focused on the direct and indirect effects of a changing climate on contemporary ranges, which are much reduced from historic ranges owing to past habitat loss and no
By
Water Resources, Ecosystems, Fort Collins Science Center, Colorado Water Science Center

Past and future warming of a deep European lake (Lake Lugano): What are the climatic drivers?

We used four decades (1972–2013) of temperature data from Lake Lugano, Switzerland and Italy, to address the hypotheses that: [i] the lake has been warming; [ii] part of the warming reflects global trends and is independent from climatic oscillations and [iii] the lake will continue to warm until the end of the 21st century. During the time spanned by our data, the surface waters of the lake (0–5
By
Ecosystems, Fort Collins Science Center

Indirect consequences of hypolimnetic hypoxia on zooplankton growth in a large eutrophic lake

Diel vertical migration (DVM) of some zooplankters in eutrophic lakes is often compressed during peak hypoxia. To better understand the indirect consequences of seasonal hypolimnetic hypoxia, we integrated laboratory-based experimental and field-based observational approaches to quantify how compressed DVM can affect growth of a cladoceran, Daphnia mendotae, in central Lake Erie, North America. To

Evidence of hypoxic foraging forays by yellow perch (<i>Perca flavescens</i>) and potential consequences for prey consumption

Previous studies in a variety of ecosystems have shown that ecologically and economically important benthic and bentho-pelagic fishes avoid hypoxic (

Changes in biological communities of the Fountain Creek Basin, Colorado, 2003–2016, in relation to antecedent streamflow, water quality, and habitat

The analysis described in this report is part of a longterm project monitoring the biological communities, habitat, and water quality of the Fountain Creek Basin. Biology, habitat, and water-quality data have been collected at 10 sites since 2003. These data include annual samples of aquatic invertebrate communities, fish communities, water quality, and quantitative riverine habitat. This report e
By
Water Resources, Colorado Water Science Center

Pre-USGS Publications

Isaak, D.J., C.C. Muhlfeld, A.S. Todd, R. Al-Chokhatchy, J.J. Roberts, K.D. Fausch, J.L. Kershner, and S.W. Hostetler. 2012 The past as prelude to the future: Retrospective assessments for anticipating future climate vulnerabilities of salmonid fishes in the Rocky Mountain West. Fisheries 37(12): 542-556.
Goto, D., K. Lindelof, D.L. Fanslow, S.A. Ludsin, J.J. Roberts, H.A. Vanderploeg, A.F. Wilson, and T.O. Höök. 2012. Indirect consequences of hypolimnetic hypoxia on
zooplankton growth in a large eutrophic lake. Aquatic Biology 16: 217-227.
Roberts, J.J., P.A. Grecay, S.A. Ludsin, S.A. Pothoven, H.A. Vanderploeg, and T.O. Höök. 2012 Evidence of hypoxic foraging forays by yellow perch (Perca flavescens) and potential consequences for prey consumption. Freshwater Biology 57: 922-937.
Roberts, J.J., T.O. Hook, S.A. Ludsin, S.A. Pothoven, H.A. Vanderploeg, and S.B. Brandt. 2009. Effects of hypolimnetic hypoxia in Lake Erie's central basin on foraging and distribution of yellow perch. Journal of Experimental Marine Biology and Ecology. 131:S132-S142.
Roberts, J.J. and F.J. Rahel. 2008. Irrigation canals as sink habitat for trout and other fishes in a Wyoming drainage. Transactions of the American Fisheries Society. 137:951-961.
Roberts, J.J. and F.J. Rahel. 2005. Accuracy of aerial telemetry in fisheries studies. North American Journal of Fisheries Management. 25:660-666.
Roberts, J.J. 2010. The ecological consequences of hypoxia for yellow perch (Perca flavescens) in Lake Erie. Doctoral Dissertation. 181 pp.

Science and Products

  • Science
    link
    A cutthroat trout up close. James Roberts photo. USGS.

    Climate Change and Trout

    Cold-water fishes like trout, salmon, and charr are especially vulnerable to shifting conditions related to climate change; for example, warmer temperatures and more variable hydroclimate. Native cutthroat trout of the southern Rocky Mountains now only occupy a tiny fraction of their historic habitats because of stressors such as non-native fishes, habitat fragmentation, and detrimental land...
    By
    Ecosystems, Fisheries Program, Fort Collins Science Center
    link

    Climate Change and Trout

    Cold-water fishes like trout, salmon, and charr are especially vulnerable to shifting conditions related to climate change; for example, warmer temperatures and more variable hydroclimate. Native cutthroat trout of the southern Rocky Mountains now only occupy a tiny fraction of their historic habitats because of stressors such as non-native fishes, habitat fragmentation, and detrimental land...
    Learn More
    link
    Cover image SIR 2017-5162

    Characterization of Water Quality and Biology in the Fountain Creek Watershed

    Monument and Fountain Creeks and their respective watersheds, located in the Front Range of Colorado, serve as important drainages for surface runoff, waste-water treatment operations, and as a water supply for downstream agricultural needs. As population growth continues in these watersheds, more and more pressures are being applied to the receiving streams, especially Fountain Creek.
    By
    Colorado Water Science Center
    link

    Characterization of Water Quality and Biology in the Fountain Creek Watershed

    Monument and Fountain Creeks and their respective watersheds, located in the Front Range of Colorado, serve as important drainages for surface runoff, waste-water treatment operations, and as a water supply for downstream agricultural needs. As population growth continues in these watersheds, more and more pressures are being applied to the receiving streams, especially Fountain Creek.
    Learn More
    link
    A cutthroat trout up close. James Roberts photo. USGS.

    Ecological Responses to Fish Reclamation Treatments

    Piscicides have been used in Rocky Mountain stream and lakes to restore native fish populations. In the last two decades concerns over piscicide effects to non-target organisms, primarily aquatic invertebrates, has increased. Although piscicides have been used for more than 70 years the impact to invertebrate assemblages has not been well studied and is largely unknown. Given the importance a...
    By
    Ecosystems, Water Resources, Environments Program, Fisheries Program, Fort Collins Science Center
    link

    Ecological Responses to Fish Reclamation Treatments

    Piscicides have been used in Rocky Mountain stream and lakes to restore native fish populations. In the last two decades concerns over piscicide effects to non-target organisms, primarily aquatic invertebrates, has increased. Although piscicides have been used for more than 70 years the impact to invertebrate assemblages has not been well studied and is largely unknown. Given the importance a...
    Learn More
    link
    Scientists work on insect traps in the Prairie Pothole region of North Dakota.

    Aquatic Ecology and Contaminants

    The Aquatic Ecology and Contaminants Team investigates critical ecological processes operating in aquatic and riparian ecosystems and how these processes are affected by human activities. We address questions through a combination of field studies, laboratory experiments, and modeling, while working at multiple levels of biological organization from cells through ecosystems. Topics include land...
    By
    Fort Collins Science Center
    link

    Aquatic Ecology and Contaminants

    The Aquatic Ecology and Contaminants Team investigates critical ecological processes operating in aquatic and riparian ecosystems and how these processes are affected by human activities. We address questions through a combination of field studies, laboratory experiments, and modeling, while working at multiple levels of biological organization from cells through ecosystems. Topics include land...
    Learn More
    link
    Native westslope cutthroat trout swim in the north fork of the Flathead River in northwestern Montana.

    The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

    Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
    By
    Climate Adaptation Science Centers, Climate Adaptation Science Center
    link

    The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

    Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
    Learn More
    link
    Native westslope cutthroat trout swim in the north fork of the Flathead River in northwestern Montana.

    The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

    Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
    By
    Climate Adaptation Science Centers, Climate Adaptation Science Center
    link

    The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.

    Salmonids (a family of fish that includes salmon, trout, and char) are a keystone species for both aquatic and terrestrial ecosystems, and can be an early warning indicator of ecosystem health. Salmonids also have strong societal values and contribute enormously to regional economies and Native American cultures. Today, many native salmonid populations are small, highly fragmented, and isolated fr
    Learn More
  • Data

    Dataset for temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river

    The trace element selenium is an essential element with a narrow window between concentrations needed to support life and those that cause toxicity to egg laying organisms. Selenium bioaccumulation in aquatic organisms is primarily the result of trophic transfer through food webs and is poorly predicted by dissolved concentrations in freshwater bodies. To better understand the hydrologic and biolo
    By
    Wyoming-Montana Water Science Center

    Invertebrate community data from native trout lakes and streams in the Southern Rocky Mountains

    Native trout in the West suffer a high degree of vulnerability, as highlighted by cutthroat trout, a group of 14 subspecies, most of which have been petitioned for listing under the Endangered Species Act (ESA). In the Southern Rocky Mountains, greenback cutthroat trout (Oncorhynchus clarkii stomias; GBCT) are listed as threatened under the ESA, and few populations remain, in part because of the i
    By
    Colorado Water Science Center

    Multimetric Index macroinvertebrate values from the Fountain Creek Basin, Colorado 2005 to 2016.

    These data have been collected as part of a cooperative project in between the U.S. Geological Survey Colorado Water Science Center, Colorado Springs Utility, and Colorado Springs Engineering. This project began in 2005 and has collected macroinvertebrate samples from Fountain Creek and its tributaries to monitor the biological condition of this watershed. Provided in this data release are Multime
    By
    Fort Collins Science Center

    Datasets of ecological communities (invertebrates and fish), streamflow, habitat, and water quality to examine the presence of trends in ecological communities from the Fountain Creek basin, Colorado, USA, 2003-2016.

    These data were used for an analysis as part of a long-term project monitoring the biological communities, habitat, and water quality of the Fountain Creek Basin. Biology, habitat, and water quality data have been collected at 10 sites starting in 2003. These data include annual samples of aquatic invertebrate communities, fish communities, water quality, and quantitative riverine habitat collecte
    By
    Colorado Water Science Center
  • Publications
    Filter Total Items: 18

    The past as prelude to the future for understanding 21st-century climate effects on Rocky Mountain Trout

    Bioclimatic models predict large reductions in native trout across the Rocky Mountains in the 21st century but lack details about how changes will occur. Through five case histories across the region, we explore how a changing climate has been affecting streams and the potential consequences for trout. Monitoring records show trends in temperature and hydrographs consistent with a warming climate
    By
    Ecosystems, Northern Rocky Mountain Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geology, Geophysics, and Geochemistry Science Center

    Fragmentation and thermal risks from climate change interact to affect persistence of native trout in the Colorado River basin

    Impending changes in climate will interact with other stressors to threaten aquatic ecosystems and their biota. Native Colorado River cutthroat trout (CRCT; Oncorhynchus clarkii pleuriticus) are now relegated to 309 isolated high-elevation (>1700 m) headwater stream fragments in the Upper Colorado River Basin, owing to past nonnative trout invasions and habitat loss. Predicted changes in climat

    Assessing and addressing the re-eutrophication of Lake Erie: central basin hypoxia

    Relieving phosphorus loading is a key management tool for controlling Lake Erie eutrophication. During the 1960s and 1970s, increased phosphorus inputs degraded water quality and reduced central basin hypolimnetic oxygen levels which, in turn, eliminated thermal habitat vital to cold-water organisms and contributed to the extirpation of important benthic macroinvertebrate prey species for fishes.
    By
    Ecosystems, Great Lakes Science Center

    Effects of hypoxia on consumption, growth, and RNA:DNA ratios of young Yellow Perch

    As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species

    Seasonal and interannual effects of hypoxia on fish habitat quality in central Lake Erie

    1. Hypoxia occurs seasonally in many stratified coastal marine and freshwater ecosystems when bottom dissolved oxygen (DO) concentrations are depleted below 2–3 mg O2 L-1. 2. We evaluated the effects of hypoxia on fish habitat quality in the central basin of Lake Erie from 1987 to 2005, using bioenergetic growth rate potential (GRP) as a proxy for habitat quality. We compared the effect of hypoxi

    Thermal regimes of Rocky Mountain lakes warm with climate change

    Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess th
    By
    Water Resources, Climate Research and Development Program, Land Change Science Program, Colorado Water Science Center

    Effects of internal phosphorus loadings and food-web structure on the recovery of a deep lake from eutrophication

    We used monitoring data from Lake Lugano (Switzerland and Italy) to assess key ecosystem responses to three decades of nutrient management (1983–2014). We investigated whether reductions in external phosphorus loadings (Lext) caused declines in lake phosphorus concentrations (P) and phytoplankton biomass (Chl a), as assumed by the predictive models that underpinned the management plan. Additionall
    By
    Water Resources, Colorado Water Science Center

    Nonnative trout invasions combined with climate change threaten persistence of isolated cutthroat trout populations in the southern Rocky Mountains

    Effective conservation of Cutthroat Trout Oncorhynchus clarkii lineages native to the Rocky Mountains will require estimating effects of multiple stressors and directing management toward the most important ones. Recent analyses have focused on the direct and indirect effects of a changing climate on contemporary ranges, which are much reduced from historic ranges owing to past habitat loss and no
    By
    Water Resources, Ecosystems, Fort Collins Science Center, Colorado Water Science Center

    Past and future warming of a deep European lake (Lake Lugano): What are the climatic drivers?

    We used four decades (1972–2013) of temperature data from Lake Lugano, Switzerland and Italy, to address the hypotheses that: [i] the lake has been warming; [ii] part of the warming reflects global trends and is independent from climatic oscillations and [iii] the lake will continue to warm until the end of the 21st century. During the time spanned by our data, the surface waters of the lake (0–5
    By
    Ecosystems, Fort Collins Science Center

    Indirect consequences of hypolimnetic hypoxia on zooplankton growth in a large eutrophic lake

    Diel vertical migration (DVM) of some zooplankters in eutrophic lakes is often compressed during peak hypoxia. To better understand the indirect consequences of seasonal hypolimnetic hypoxia, we integrated laboratory-based experimental and field-based observational approaches to quantify how compressed DVM can affect growth of a cladoceran, Daphnia mendotae, in central Lake Erie, North America. To

    Evidence of hypoxic foraging forays by yellow perch (<i>Perca flavescens</i>) and potential consequences for prey consumption

    Previous studies in a variety of ecosystems have shown that ecologically and economically important benthic and bentho-pelagic fishes avoid hypoxic (

    Changes in biological communities of the Fountain Creek Basin, Colorado, 2003–2016, in relation to antecedent streamflow, water quality, and habitat

    The analysis described in this report is part of a longterm project monitoring the biological communities, habitat, and water quality of the Fountain Creek Basin. Biology, habitat, and water-quality data have been collected at 10 sites since 2003. These data include annual samples of aquatic invertebrate communities, fish communities, water quality, and quantitative riverine habitat. This report e
    By
    Water Resources, Colorado Water Science Center

    Pre-USGS Publications

    Isaak, D.J., C.C. Muhlfeld, A.S. Todd, R. Al-Chokhatchy, J.J. Roberts, K.D. Fausch, J.L. Kershner, and S.W. Hostetler. 2012 The past as prelude to the future: Retrospective assessments for anticipating future climate vulnerabilities of salmonid fishes in the Rocky Mountain West. Fisheries 37(12): 542-556.
    Goto, D., K. Lindelof, D.L. Fanslow, S.A. Ludsin, J.J. Roberts, H.A. Vanderploeg, A.F. Wilson, and T.O. Höök. 2012. Indirect consequences of hypolimnetic hypoxia on
    zooplankton growth in a large eutrophic lake. Aquatic Biology 16: 217-227.
    Roberts, J.J., P.A. Grecay, S.A. Ludsin, S.A. Pothoven, H.A. Vanderploeg, and T.O. Höök. 2012 Evidence of hypoxic foraging forays by yellow perch (Perca flavescens) and potential consequences for prey consumption. Freshwater Biology 57: 922-937.
    Roberts, J.J., T.O. Hook, S.A. Ludsin, S.A. Pothoven, H.A. Vanderploeg, and S.B. Brandt. 2009. Effects of hypolimnetic hypoxia in Lake Erie's central basin on foraging and distribution of yellow perch. Journal of Experimental Marine Biology and Ecology. 131:S132-S142.
    Roberts, J.J. and F.J. Rahel. 2008. Irrigation canals as sink habitat for trout and other fishes in a Wyoming drainage. Transactions of the American Fisheries Society. 137:951-961.
    Roberts, J.J. and F.J. Rahel. 2005. Accuracy of aerial telemetry in fisheries studies. North American Journal of Fisheries Management. 25:660-666.
    Roberts, J.J. 2010. The ecological consequences of hypoxia for yellow perch (Perca flavescens) in Lake Erie. Doctoral Dissertation. 181 pp.