James Roberts is a Research Ecologist based in Huron, 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
Publications by this scientist
Stream size, temperature, and density explain body sizes of freshwater salmonids across a range of climate conditions
Fisheries research and monitoring activities of the Lake Erie Biological Station, 2020
Temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river
Mercury and selenium concentrations in fishes of the Upper Colorado River Basin, southwestern United States: A retrospective assessment
Predicting persistence of Rio Grande Cutthroat Trout populations in an uncertain future
Estimating lake–climate responses from sparse data: An application to high elevation lakes
Comparability among four invertebrate sampling methods and two multimetric indexes, Fountain Creek Basin, Colorado, 2010–2012
Changes in biological communities of the Fountain Creek Basin, Colorado, 2003–2016, in relation to antecedent streamflow, water quality, and habitat
Thermal regimes of Rocky Mountain lakes warm with climate change
Effects of internal phosphorus loadings and food-web structure on the recovery of a deep lake from eutrophication
Nonnative trout invasions combined with climate change threaten persistence of isolated cutthroat trout populations in the southern Rocky Mountains
Past and future warming of a deep European lake (Lake Lugano): What are the climatic drivers?
Non-USGS Publications**
zooplankton growth in a large eutrophic lake. Aquatic Biology 16: 217-227.
**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.
Science pages by this scientist
Aquatic Ecology and Contaminants
Ecological Responses to Fish Reclamation Treatments
Climate Change and Trout
Characterization of Water Quality and Biology in the Fountain Creek Watershed
The Past as a Prelude to the Future: Assessing Climate Effects on Native Trout in the U.S.
Data releases by this scientist
Dataset for temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river
Invertebrate community data from native trout lakes and streams in the Southern Rocky Mountains
Fish tissue mercury and selenium concentrations in Upper Colorado River Basin: 1962-2011
Multimetric Index macroinvertebrate values from the Fountain Creek Basin, Colorado 2005 to 2016.
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.
Science and Products
- Publications
Publications by this scientist
Filter Total Items: 19Stream size, temperature, and density explain body sizes of freshwater salmonids across a range of climate conditions
Climate change and anthropogenic activities are altering the body sizes of fishes, yet our understanding of factors influencing body size for many taxa remains incomplete. We evaluated the relationships between climate, environmental, and landscape attributes and the body size of different taxa of freshwater trout (Salmonidae) in the USA. Hierarchical spatial modeling across a gradient of habitatsFisheries research and monitoring activities of the Lake Erie Biological Station, 2020
This report presents biomass-based summaries of fish communities in the West Basin of Lake Erie derived from USGS bottom trawl surveys conducted from 2013 to 2020 during June and September. The survey design provided temporal and spatial coverage that did not exist in the interagency trawl database, and thus complemented the August ODNR-OMNRF effort to reinforce stock assessments with more robustTemporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river
Hydrologic and irrigation regimes mediate the timing of selenium (Se) mobilization to rivers, but the extent to which patterns in Se uptake and trophic transfer through recipient food webs reflect the temporal variation in Se delivery is unknown. We investigated Se mobilization, partitioning, and trophic transfer along approximately 60 river miles of the selenium-impaired segment of the Lower GunnMercury and selenium concentrations in fishes of the Upper Colorado River Basin, southwestern United States: A retrospective assessment
Mercury (Hg) and selenium (Se) are contaminants of concern for fish in the Upper Colorado River Basin (UCRB). We explored Hg and Se in fish tissues (2,324 individuals) collected over 50 years (1962–2011) from the UCRB. Samples include native and non-native fish collected from lotic waterbodies spanning 7 major tributaries to the Colorado River. There was little variation of total mercury (THg) inPredicting persistence of Rio Grande Cutthroat Trout populations in an uncertain future
The Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis (RGCT ) occupies just 12% of its ancestral range. As the southernmost subspecies of Cutthroat Trout, we expect a warming climate to bring additional stressors to RGCT populations, such as increased stream temperatures, reduced streamflows, and increased incidence of wildfire. We developed a Bayesian network (BN ) model using site‐speciEstimating lake–climate responses from sparse data: An application to high elevation lakes
Although many studies demonstrate lake warming, few document trends from lakes with sparse data. Diel and seasonal variability of surface temperatures limit conventional trend analyses to datasets with frequent repeated observations. Thus, remote lakes, including many high elevation lakes, are underrepresented in trend analyses. We used a Bayesian technique to analyze sparse data that explicitly iComparability among four invertebrate sampling methods and two multimetric indexes, Fountain Creek Basin, Colorado, 2010–2012
The U.S. Geological Survey (USGS), in cooperation with Colorado Springs City Engineering and Colorado Springs Utilities, analyzed previously collected invertebrate data to determine the comparability among four sampling methods and two versions (2010 and 2017) of the Colorado Benthic Macroinvertebrate Multimetric Index (MMI). For this study, annual macroinvertebrate samples were collected concurreChanges 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 eThermal 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 thEffects 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. AdditionallNonnative 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 noPast 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 (0–5Non-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.
- Science
Science pages by this scientist
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...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...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...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.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 - Data
Data releases by this scientist
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 bioloInvertebrate 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 iFish tissue mercury and selenium concentrations in Upper Colorado River Basin: 1962-2011
These data were compiled to study mercury and selenium concentrations in fish species and assemblages in lotic waterbodies across the Upper Colorado River Basin. Data were compiled from State and Federal agencies. This data table contains raw concentration data, as well as standardized concentrations corrected for differences based on sample type (i.e., tissue type), species-specific bioaccumulatiMultimetric 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 MultimeDatasets 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 - Multimedia