James J Roberts, PhD
James J Roberts is a Research Fisheries Biologist based in Huron, OH.
James has broad research expertise and investigates the ecological consequences of stressors like invasive species, climate change, and eutrophication for aquatic systems and specifically fish populations. There are three overall themes his research is split between (Invasive species, native fish ecology/conservation, and climate changes effects) which are all related to the conservation and management of aquatic species and systems.
Currently, he is investigating the movement, behavior, and habitat use of Grass Carp, an invasive species in the Great Lakes. 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 studied the effects (behavioral, physiological, and inter-specific) of hypoxia on the benthic fish assemblage of Lake Erie, while focusing on yellow perch. Previously, James has explored the potential effects climate change may have on the persistence of Cutthroat Trout in stream and lake habitats throughout the Southern Rocky Mountain region."
Professional Experience
Research Fisheries Biologist, USGS 2020-present; Great Lakes Science Center
Fish Biologist, USGS 2015-2020; Colorado Water Science Center
Research Ecologist-Mendenhall Fellow, USGS 2012-2015; Fort Collins Science Center
Education and Certifications
Ph.D. University of Michigan
M.S. University of Wyoming
B.S. University of Michigan
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Filter Total Items: 22
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
Authors
Fabio Lepori, James Roberts
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
Authors
James Roberts, Kurt D. Fausch, Mevin Hooten, Douglas P. Peterson
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
Authors
Fabio Lepori, James Roberts
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.
Authors
Donald Scavia, J. David Allan, Kristin K. Arend, Steven Bartell, Dmitry Beletsky, Nate S. Bosch, Stephen B. Brandt, Ruth D. Briland, Irem Daloğlu, Joseph V. DePinto, David M. Dolan, Mary Anne Evans, Troy M. Farmer, Daisuke Goto, Haejin Han, Tomas O. Höök, Roger Knight, Stuart A. Ludsin, Doran Mason, Anna M. Michalak, R. Peter Richards, James Roberts, Daniel K. Rucinski, Edward Rutherford, David J. Schwab, Timothy M. Sesterhenn, Hongyan Zhang, Yuntao Zhou
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
Authors
James Roberts, Kurt D. Fausch, Douglas P. Peterson, Mevin Hooten
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
Authors
Daniel J. Isaak, Clint C. Muhlfeld, Andrew S. Todd, Robert Al-chokhachy, James Roberts, Jeffrey L. Kershner, Kurt D. Fausch, Steven W. Hostetler
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
Authors
Daisuke Goto, Kara Lindelof, David L. Fanslow, Stuart A. Ludsin, Steven A. Pothoven, James Roberts, Henry A. Vanderploeg, Alan E. Wilson, Tomas O. Höök
Evidence of hypoxic foraging forays by yellow perch (Perca flavescens) 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 (
Authors
James Roberts, Paul A. Grecay, Stuart A. Ludsin, Steve A. Pothoven, Henry A. Vanderploeg, Tomas O. Höök
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
Authors
James Roberts, Stephen B. Brandt, David Fanslow, Stuart A. Ludsin, Steven A. Pothoven, Donald Scavia, Tomas O. Höök
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
Authors
Kristin K. Arend, Dmitry Beletsky, Joseph DePinto, Stuart A. Ludsin, James Roberts, Daniel K. Rucinski, Donald Scavia, David J. Schwab, Tomas O. Höök
Non-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.
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.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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Filter Total Items: 22Effects 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. AdditionallAuthorsFabio Lepori, James RobertsNonnative 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 noAuthorsJames Roberts, Kurt D. Fausch, Mevin Hooten, Douglas P. PetersonPast 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 (0–5AuthorsFabio Lepori, James RobertsAssessing 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.AuthorsDonald Scavia, J. David Allan, Kristin K. Arend, Steven Bartell, Dmitry Beletsky, Nate S. Bosch, Stephen B. Brandt, Ruth D. Briland, Irem Daloğlu, Joseph V. DePinto, David M. Dolan, Mary Anne Evans, Troy M. Farmer, Daisuke Goto, Haejin Han, Tomas O. Höök, Roger Knight, Stuart A. Ludsin, Doran Mason, Anna M. Michalak, R. Peter Richards, James Roberts, Daniel K. Rucinski, Edward Rutherford, David J. Schwab, Timothy M. Sesterhenn, Hongyan Zhang, Yuntao ZhouFragmentation 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 climatAuthorsJames Roberts, Kurt D. Fausch, Douglas P. Peterson, Mevin HootenThe 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 climateAuthorsDaniel J. Isaak, Clint C. Muhlfeld, Andrew S. Todd, Robert Al-chokhachy, James Roberts, Jeffrey L. Kershner, Kurt D. Fausch, Steven W. HostetlerIndirect 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. ToAuthorsDaisuke Goto, Kara Lindelof, David L. Fanslow, Stuart A. Ludsin, Steven A. Pothoven, James Roberts, Henry A. Vanderploeg, Alan E. Wilson, Tomas O. HöökEvidence of hypoxic foraging forays by yellow perch (Perca flavescens) 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 (AuthorsJames Roberts, Paul A. Grecay, Stuart A. Ludsin, Steve A. Pothoven, Henry A. Vanderploeg, Tomas O. HöökEffects 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 speciesAuthorsJames Roberts, Stephen B. Brandt, David Fanslow, Stuart A. Ludsin, Steven A. Pothoven, Donald Scavia, Tomas O. HöökSeasonal 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 hypoxiAuthorsKristin K. Arend, Dmitry Beletsky, Joseph DePinto, Stuart A. Ludsin, James Roberts, Daniel K. Rucinski, Donald Scavia, David J. Schwab, Tomas O. HöökNon-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.**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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