Theodore Kennedy, Ph.D.
I use food webs to describe ecosystem response to river regulation and biological invasions. I have been with USGS since 2004, providing science in support of the Glen Canyon Dam Adaptive Management Program.
Professional Experience
11/04 - present: Research Ecologist, Grand Canyon Monitoring and Research Center, Southwest Biological Science Center, US Geological Survey, Flagstaff, AZ
1/04 - 11/04: Postdoctoral researcher, Arizona State University
1/03 - 1/04: Postdoctoral researcher, Grand Canyon Monitoring and Research Center, Southwest Biological Science Center, US Geological Survey, Flagstaff, AZ.
Education and Certifications
9/96 - 12/02: Ph.D. in Ecology, Dept. of Ecology, Evolution, and Behavior, University of Minnesota. Dissertation title: The causes and consequences of plant invasions
1/90 - 12/94: B.S. in Ecology, California Polytechnic State University at San Luis Obispo, cum laude.
Science and Products
Filter Total Items: 15
Angel Lichen Moth Abundance and Morphology Data, Grand Canyon, AZ, 2012 Angel Lichen Moth Abundance and Morphology Data, Grand Canyon, AZ, 2012
Two unique datasets on the abundance and morphology of the angel lichen moth (Cisthene angelus) in Grand Canyon, Arizona, USA were compiled to describe the phenology and life history of this common, but poorly known, species. The abundance data were collected from 2012 to 2013 through a collaboration with river runners in Grand Canyon National Park. These citizen scientists deployed...
Flow management for hydropower extirpates aquatic insects, undermining river food websData Flow management for hydropower extirpates aquatic insects, undermining river food websData
Two unique datasets were gathered to document whether flow management for hydropower affects the abundance and diversity of aquatic insect assemblages. The first dataset was collected in Grand Canyon from 2012-2014 by citizen scientists rafting the Colorado River. Simple light traps were set out each night in camp and used to capture the adult life stages of aquatic insects that emerged...
Flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western North AmericaData Flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western North AmericaData
This data is a compilation of fishery monitoring data collected by state agencies over several decades in tailwaters downriver of dams in Colorado, Utah, Montana, Wyoming, Idaho, New Mexico, Arizona, California, and Oregon. Specifically, the data contained herein is summary data used in four generalized linear mixed models that were developed to assess the biological and hydrologic...
Filter Total Items: 62
Applied citizen science in freshwater research Applied citizen science in freshwater research
Worldwide, scientists are increasingly collaborating with the general public. Citizen science methods are readily applicable to freshwater research, monitoring, and education. In addition to providing cost-effective data on spatial and temporal scales that are otherwise unattainable, citizen science provides unique opportunities for engagement with local communities and stakeholders in...
Authors
Anya Metcalfe, Theodore Kennedy, Gabriella Mendez, Jeffrey Muehlbauer
As the prey thickens: Rainbow trout select prey based upon width not length As the prey thickens: Rainbow trout select prey based upon width not length
Drift-feeding fish are typically considered size-selective predators. Yet, few studies have explicitly tested which aspect of prey “size” best explains size selection by drift-foraging fish. Here, we develop a Bayesian discrete choice model to evaluate how attributes of both prey and predator simultaneously influence size-selective foraging. We apply the model to a large dataset of...
Authors
Michael Dodrill, Charles Yackulic, Theodore Kennedy, Michael Yard, Josh Korman
Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin
River biodiversity is threatened globally by hydropower dams, and there is a need to understand how dam management favors certain species while filtering out others. We examined aquatic invertebrate communities within the tailwaters 0–24 km downstream of seven large hydropower dams in the Colorado River Basin of the western United States. We quantified aquatic invertebrate dominance...
Authors
Erin Abernathy, Jeffrey Muehlbauer, Theodore Kennedy, Jonathan Tonkin, Richard Van Driesche, David Lytle
Water storage decisions will determine the distribution and persistence of imperiled river fishes Water storage decisions will determine the distribution and persistence of imperiled river fishes
Managing the world’s freshwater supply to meet societal and environmental needs in a changing climate is one of the biggest challenges for the 21st century. Dams provide water security, however, the allocation of dwindling water supply among reservoirs could exacerbate or ameliorate the effects of climate change on aquatic communities. Here, we show that the relative sensitivity of river...
Authors
Kimberly Dibble, Charles Yackulic, Theodore Kennedy, Kevin Bestgen, John Schmidt
Net-spinning caddisfly distribution in large regulated rivers Net-spinning caddisfly distribution in large regulated rivers
Most of the world's large rivers are dammed for the purposes of water storage, flood control, and power production. Damming rivers fundamentally alters water temperature and flows in tailwater ecosystems, which in turn affects the presence and abundance of downstream biota.We collaborated with more than 200 citizen scientists to collect 2,194 light trap samples across 2 years and more...
Authors
Anya Metcalfe, Jeffrey Muehlbauer, Theodore Kennedy, Charles Yackulic, Kimberly Dibble, Jane Marks
Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a fish population Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a fish population
Somatic growth exerts strong control on patterns in the abundance of animal populations via effects on maturation, fecundity, and survival rates of juveniles and adults. In this paper, we quantify abiotic and biotic drivers of rainbow trout growth in the Colorado River, AZ, and the resulting impact on spatial and temporal variation in abundance. Inferences are based on approximately 10...
Authors
Josh Korman, Michael Yard, Maria Dzul, Charles Yackulic, Michael Dodrill, Bridget Deemer, Theodore Kennedy
Macroinvertebrate oviposition habitat selectivity and egg-mass desiccation tolerances: Implications for population dynamics in large regulated rivers Macroinvertebrate oviposition habitat selectivity and egg-mass desiccation tolerances: Implications for population dynamics in large regulated rivers
Aquatic insects exhibit complex life cycles that include egg, larval, adult, and, in some instances, pupal stages. Disturbances at any of these life stages can affect overall population dynamics. Yet, efforts to understand the effects of disturbances, such as hydrologic alterations, overwhelmingly focus on the larval life stage of aquatic insects. We evaluated the potential for load...
Authors
Scott Miller, Matt Schroer, Jesse Fleri, Theodore Kennedy
Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon
Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator...
Authors
David Walters, Wyatt F. Cross, Theodore Kennedy, Colden V. Baxter, R. O. Hall, Emma Rosi
Spatial population structure of a widespread aquatic insect in the Colorado River Basin: Evidence for a Hydropsyche oslari species complex Spatial population structure of a widespread aquatic insect in the Colorado River Basin: Evidence for a Hydropsyche oslari species complex
Structural connectivity and dispersal ability are important constraints on functional connectivity among populations. For aquatic organisms that disperse among stream corridors, the regional structure of a river network can, thus, define the boundaries of gene flow. In this study, we used mitochondrial DNA (mtCO1 barcoding gene) to examine the genetic diversity and population structure...
Authors
Anya Metcalfe, Theodore Kennedy, Jane Marks, Aaron Smith, Jeffrey Muehlbauer
Bug flows: Don’t count your midges until they hatch Bug flows: Don’t count your midges until they hatch
Usually when people hear about a “bug problem” it’s due to an undesirable overabundance of insects (think plague of locusts). In the Colorado River in Grand Canyon, however, we are faced with the opposite predicament: the river is essentially devoid of bugs. Aquatic insects are a fundamental component of a healthy river ecosystem. Most aquatic insects spend their juvenile life stages...
Authors
Anya Metcalfe, Jeffrey Muehlbauer, Morgan Ford, Theodore Kennedy
Warm water temperatures and shifts in seasonality increase trout recruitment but only moderately decrease adult size in western North American tailwaters Warm water temperatures and shifts in seasonality increase trout recruitment but only moderately decrease adult size in western North American tailwaters
Dams throughout western North America have altered thermal regimes in rivers, creating cold, clear “tailwaters” in which trout populations thrive. Ongoing drought in the region has led to highly publicized reductions in reservoir storage and raised concerns about potential reductions in downstream flows. Large changes in riverine thermal regimes may also occur as reservoir water levels...
Authors
Kimberly Dibble, Charles Yackulic, Theodore Kennedy
Brown trout in the Lees Ferry reach of the Colorado River—Evaluation of causal hypotheses and potential interventions Brown trout in the Lees Ferry reach of the Colorado River—Evaluation of causal hypotheses and potential interventions
Over the period 2014–2016, the number of nonnative brown trout (Salmo trutta) captured during routine monitoring in the Lees Ferry reach of the Colorado River, downstream of Glen Canyon Dam, began increasing. Management agencies and stakeholders have questioned whether the increase in brown trout in the Lees Ferry reach represents a threat to the endangered humpback chub (Gila cypha), to...
Authors
Michael Runge, Charles Yackulic, Lucas Bair, Theodore Kennedy, Richard Valdez, Craig Ellsworth, Jeffrey L. Kershner, R. Rogers, Melissa Trammell, Kirk Young
Non-USGS Publications**
Kennedy, T.A., 1998, Patterns of an invasion by Argentine ants (Linepithema humile) in a riparian corridor and its effects on ant diversity: The American Midland Naturalist, v. 140, p. 343-350.
Naeem, S., Knops, J.M., Tilman, D., Howe, K.M., Kennedy, T. and Gale, S., 2000, Plant diversity increases resistance to invasion in the absence of covarying extrinsic factors: Oikos, v. 91, p. 97-108, DOI: 10.1034/j.1600-0706.2000.910108.x.
Raffaelli, D., Van der Putten, W.H., Persson, L., Wardle, D.A., Petchey, O.L., Koricheva, J., Van Der Heijden, M., Mikola, J. and Kennedy, T., 2002, Multi-trophic dynamics and ecosystem processes, In Loreau, M., Naeem, S., and Inchausti, P., eds., Biodiversity and ecosystem functioning: synthesis and perspectives: Oxford, Oxford University Press, p.147-154.
Levine, J.M., Kennedy, T., and Naeem, S., 2002, Neighborhood scale effects of species diversity on biological invasions and their relationship to community patterns, In Loreau, M., Naeem, S., and Inchausti, P., eds., Biodiversity and ecosystem functioning: synthesis and perspectives: Oxford, Oxford University Press, p.114-124.
Kennedy, T.A., Naeem, S., Howe, K.M., Knops, J.M., Tilman, D., and Reich, P., 2002, Biodiversity as a barrier to ecological invasion. Nature, v.417, p.636. doi:10.1038/nature00776.
Kennedy, T.A., and Hobbie, S.E., 2004, Saltcedar (Tamarix ramosissima) invasion alters organic matter dynamics in a desert stream. Freshwater Biology, v. 49, p. 65-76. doi: 10.1046/j.1365-2426.2003.01166.x.
Kennedy, T.A., Finlay, J.C., and Hobbie, S.E., 2005, Eradication of invasive Tamarix ramosissima along a desert stream increases native fish density: Ecological Applications, v. 15, p. 2072-2083.
**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 and Products
Filter Total Items: 15
Angel Lichen Moth Abundance and Morphology Data, Grand Canyon, AZ, 2012 Angel Lichen Moth Abundance and Morphology Data, Grand Canyon, AZ, 2012
Two unique datasets on the abundance and morphology of the angel lichen moth (Cisthene angelus) in Grand Canyon, Arizona, USA were compiled to describe the phenology and life history of this common, but poorly known, species. The abundance data were collected from 2012 to 2013 through a collaboration with river runners in Grand Canyon National Park. These citizen scientists deployed...
Flow management for hydropower extirpates aquatic insects, undermining river food websData Flow management for hydropower extirpates aquatic insects, undermining river food websData
Two unique datasets were gathered to document whether flow management for hydropower affects the abundance and diversity of aquatic insect assemblages. The first dataset was collected in Grand Canyon from 2012-2014 by citizen scientists rafting the Colorado River. Simple light traps were set out each night in camp and used to capture the adult life stages of aquatic insects that emerged...
Flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western North AmericaData Flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western North AmericaData
This data is a compilation of fishery monitoring data collected by state agencies over several decades in tailwaters downriver of dams in Colorado, Utah, Montana, Wyoming, Idaho, New Mexico, Arizona, California, and Oregon. Specifically, the data contained herein is summary data used in four generalized linear mixed models that were developed to assess the biological and hydrologic...
Filter Total Items: 62
Applied citizen science in freshwater research Applied citizen science in freshwater research
Worldwide, scientists are increasingly collaborating with the general public. Citizen science methods are readily applicable to freshwater research, monitoring, and education. In addition to providing cost-effective data on spatial and temporal scales that are otherwise unattainable, citizen science provides unique opportunities for engagement with local communities and stakeholders in...
Authors
Anya Metcalfe, Theodore Kennedy, Gabriella Mendez, Jeffrey Muehlbauer
As the prey thickens: Rainbow trout select prey based upon width not length As the prey thickens: Rainbow trout select prey based upon width not length
Drift-feeding fish are typically considered size-selective predators. Yet, few studies have explicitly tested which aspect of prey “size” best explains size selection by drift-foraging fish. Here, we develop a Bayesian discrete choice model to evaluate how attributes of both prey and predator simultaneously influence size-selective foraging. We apply the model to a large dataset of...
Authors
Michael Dodrill, Charles Yackulic, Theodore Kennedy, Michael Yard, Josh Korman
Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin
River biodiversity is threatened globally by hydropower dams, and there is a need to understand how dam management favors certain species while filtering out others. We examined aquatic invertebrate communities within the tailwaters 0–24 km downstream of seven large hydropower dams in the Colorado River Basin of the western United States. We quantified aquatic invertebrate dominance...
Authors
Erin Abernathy, Jeffrey Muehlbauer, Theodore Kennedy, Jonathan Tonkin, Richard Van Driesche, David Lytle
Water storage decisions will determine the distribution and persistence of imperiled river fishes Water storage decisions will determine the distribution and persistence of imperiled river fishes
Managing the world’s freshwater supply to meet societal and environmental needs in a changing climate is one of the biggest challenges for the 21st century. Dams provide water security, however, the allocation of dwindling water supply among reservoirs could exacerbate or ameliorate the effects of climate change on aquatic communities. Here, we show that the relative sensitivity of river...
Authors
Kimberly Dibble, Charles Yackulic, Theodore Kennedy, Kevin Bestgen, John Schmidt
Net-spinning caddisfly distribution in large regulated rivers Net-spinning caddisfly distribution in large regulated rivers
Most of the world's large rivers are dammed for the purposes of water storage, flood control, and power production. Damming rivers fundamentally alters water temperature and flows in tailwater ecosystems, which in turn affects the presence and abundance of downstream biota.We collaborated with more than 200 citizen scientists to collect 2,194 light trap samples across 2 years and more...
Authors
Anya Metcalfe, Jeffrey Muehlbauer, Theodore Kennedy, Charles Yackulic, Kimberly Dibble, Jane Marks
Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a fish population Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a fish population
Somatic growth exerts strong control on patterns in the abundance of animal populations via effects on maturation, fecundity, and survival rates of juveniles and adults. In this paper, we quantify abiotic and biotic drivers of rainbow trout growth in the Colorado River, AZ, and the resulting impact on spatial and temporal variation in abundance. Inferences are based on approximately 10...
Authors
Josh Korman, Michael Yard, Maria Dzul, Charles Yackulic, Michael Dodrill, Bridget Deemer, Theodore Kennedy
Macroinvertebrate oviposition habitat selectivity and egg-mass desiccation tolerances: Implications for population dynamics in large regulated rivers Macroinvertebrate oviposition habitat selectivity and egg-mass desiccation tolerances: Implications for population dynamics in large regulated rivers
Aquatic insects exhibit complex life cycles that include egg, larval, adult, and, in some instances, pupal stages. Disturbances at any of these life stages can affect overall population dynamics. Yet, efforts to understand the effects of disturbances, such as hydrologic alterations, overwhelmingly focus on the larval life stage of aquatic insects. We evaluated the potential for load...
Authors
Scott Miller, Matt Schroer, Jesse Fleri, Theodore Kennedy
Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon
Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator...
Authors
David Walters, Wyatt F. Cross, Theodore Kennedy, Colden V. Baxter, R. O. Hall, Emma Rosi
Spatial population structure of a widespread aquatic insect in the Colorado River Basin: Evidence for a Hydropsyche oslari species complex Spatial population structure of a widespread aquatic insect in the Colorado River Basin: Evidence for a Hydropsyche oslari species complex
Structural connectivity and dispersal ability are important constraints on functional connectivity among populations. For aquatic organisms that disperse among stream corridors, the regional structure of a river network can, thus, define the boundaries of gene flow. In this study, we used mitochondrial DNA (mtCO1 barcoding gene) to examine the genetic diversity and population structure...
Authors
Anya Metcalfe, Theodore Kennedy, Jane Marks, Aaron Smith, Jeffrey Muehlbauer
Bug flows: Don’t count your midges until they hatch Bug flows: Don’t count your midges until they hatch
Usually when people hear about a “bug problem” it’s due to an undesirable overabundance of insects (think plague of locusts). In the Colorado River in Grand Canyon, however, we are faced with the opposite predicament: the river is essentially devoid of bugs. Aquatic insects are a fundamental component of a healthy river ecosystem. Most aquatic insects spend their juvenile life stages...
Authors
Anya Metcalfe, Jeffrey Muehlbauer, Morgan Ford, Theodore Kennedy
Warm water temperatures and shifts in seasonality increase trout recruitment but only moderately decrease adult size in western North American tailwaters Warm water temperatures and shifts in seasonality increase trout recruitment but only moderately decrease adult size in western North American tailwaters
Dams throughout western North America have altered thermal regimes in rivers, creating cold, clear “tailwaters” in which trout populations thrive. Ongoing drought in the region has led to highly publicized reductions in reservoir storage and raised concerns about potential reductions in downstream flows. Large changes in riverine thermal regimes may also occur as reservoir water levels...
Authors
Kimberly Dibble, Charles Yackulic, Theodore Kennedy
Brown trout in the Lees Ferry reach of the Colorado River—Evaluation of causal hypotheses and potential interventions Brown trout in the Lees Ferry reach of the Colorado River—Evaluation of causal hypotheses and potential interventions
Over the period 2014–2016, the number of nonnative brown trout (Salmo trutta) captured during routine monitoring in the Lees Ferry reach of the Colorado River, downstream of Glen Canyon Dam, began increasing. Management agencies and stakeholders have questioned whether the increase in brown trout in the Lees Ferry reach represents a threat to the endangered humpback chub (Gila cypha), to...
Authors
Michael Runge, Charles Yackulic, Lucas Bair, Theodore Kennedy, Richard Valdez, Craig Ellsworth, Jeffrey L. Kershner, R. Rogers, Melissa Trammell, Kirk Young
Non-USGS Publications**
Kennedy, T.A., 1998, Patterns of an invasion by Argentine ants (Linepithema humile) in a riparian corridor and its effects on ant diversity: The American Midland Naturalist, v. 140, p. 343-350.
Naeem, S., Knops, J.M., Tilman, D., Howe, K.M., Kennedy, T. and Gale, S., 2000, Plant diversity increases resistance to invasion in the absence of covarying extrinsic factors: Oikos, v. 91, p. 97-108, DOI: 10.1034/j.1600-0706.2000.910108.x.
Raffaelli, D., Van der Putten, W.H., Persson, L., Wardle, D.A., Petchey, O.L., Koricheva, J., Van Der Heijden, M., Mikola, J. and Kennedy, T., 2002, Multi-trophic dynamics and ecosystem processes, In Loreau, M., Naeem, S., and Inchausti, P., eds., Biodiversity and ecosystem functioning: synthesis and perspectives: Oxford, Oxford University Press, p.147-154.
Levine, J.M., Kennedy, T., and Naeem, S., 2002, Neighborhood scale effects of species diversity on biological invasions and their relationship to community patterns, In Loreau, M., Naeem, S., and Inchausti, P., eds., Biodiversity and ecosystem functioning: synthesis and perspectives: Oxford, Oxford University Press, p.114-124.
Kennedy, T.A., Naeem, S., Howe, K.M., Knops, J.M., Tilman, D., and Reich, P., 2002, Biodiversity as a barrier to ecological invasion. Nature, v.417, p.636. doi:10.1038/nature00776.
Kennedy, T.A., and Hobbie, S.E., 2004, Saltcedar (Tamarix ramosissima) invasion alters organic matter dynamics in a desert stream. Freshwater Biology, v. 49, p. 65-76. doi: 10.1046/j.1365-2426.2003.01166.x.
Kennedy, T.A., Finlay, J.C., and Hobbie, S.E., 2005, Eradication of invasive Tamarix ramosissima along a desert stream increases native fish density: Ecological Applications, v. 15, p. 2072-2083.
**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.