Brian D Healy, PhD
Dr. Brian Healy is a supervisory research fish biologist at the US Geological Survey – Southwest Biological Science Center, Grand Canyon Monitoring and Research Center.
Dr. Healy’s primary research interests include ecology, conservation, and management of river and stream fishes, and specifically, studying fish population responses to changes in stream flow, disturbances, and management actions. His research is in support of decision-making in the context of water management that affects fish populations in the Colorado River, California Central Valley and San Francisco Bay Delta, as well as others.
Professional Experience
2024 - present: Supervisory Research Fish Biologist, U.S. Geological Survey, Southwest Biological Science Center
2022 - 2023: Research Biologist, Post-doctoral scholar, U.S. Geological Survey, Eastern Ecological Science Center
2009 - 2022: Fisheries Biologist/program manager, Native Fish Ecology and Conservation Program, Grand Canyon National Park
2018 - 2022: Graduate Research Assistant/Colorado River Doctoral Scholar, Watershed Sciences, Utah State University
2003 - 2009: Fisheries Biologist, White River National Forest
2000 - 2003: Fisheries Biologist, Chippewa National Forest
1999 - 2000: Graduate Research Assistant, Dept. of Wildlife and Fisheries Sciences, Texas A&M University
Education and Certifications
PhD, 2022, Utah State University, Ecology
M.S. 2002, Texas A&M University, Wildlife and Fisheries Sciences
B.S. 1998, University of Wisconsin - Eau Claire, Biology
Science and Products
Rainbow Trout in the Colorado River, Grand Canyon
Rainbow trout are a desirable sport fish that have been introduced in many locations around the world, including the Colorado River. Although introductions of rainbow trout and other nonnative fishes provide recreational fishing opportunities, they can also pose threats to native fish populations. The Glen Canyon Dam Adaptive Management Program has tasked scientists and managers with identifying...
Multicriteria decision analysis scores for rapid delta smelt decision analysis Multicriteria decision analysis scores for rapid delta smelt decision analysis
These data were compiled to support water management decision-making by the U.S. Bureau of Reclamation and California Department of Water Resources related to the Central Valley Project (CVP) and State Water Project (SWP) operations in water year 2025. The objectives of the study were to use structured decision making to assess tradeoffs between multiple competing water needs and inform...
Brown trout movement data in Glen and Grand Canyons, Arizona, USA Brown trout movement data in Glen and Grand Canyons, Arizona, USA
These data were compiled to test hypotheses regarding drivers of movement of brown trout. Objectives of our study were to test whether the degree of movement varied in response to placement of a weir in Bright Angel Creek, fall timed flooding events, or simply seasonal changes. These data represent summarized capture histories of brown trout in terms of states based on physical locations...
Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking...
Authors
Brian Healy, Phaedra E. Budy, Mary M. Conner, Emily Omana Smith
Filter Total Items: 16
Rapid structured decision making for Hypomesus transpacificus (delta smelt) summer–fall freshwater outflow management Rapid structured decision making for Hypomesus transpacificus (delta smelt) summer–fall freshwater outflow management
Managers of the Central Valley Project (CVP) and State Water Projects (SWP) in California are confronted with difficult tradeoffs between water uses and associated values affected by water management decisions. These decisions involve altering the timing and magnitude of water releases from dams and reservoirs, which can affect habitats for economically important and Federally and State...
Authors
Brian Healy, Corey Phillis, Brian Mahardja, Cameron Koizumi, Catarina Pien, Nancy Parker, J. Conrad, Julie Ekstrom, Julie Leimbach, Rafael Silberblatt, Tom Fischer, Chase Ehlo
Mixed natal origins present management challenges for a non-native fish established throughout a modified river network Mixed natal origins present management challenges for a non-native fish established throughout a modified river network
Expansion of non-native brown trout (Salmo trutta) in the Colorado River below Glen Canyon Dam motivated reevaluation of suppression strategies to minimize potential impacts to native fishes in the Grand Canyon, Arizona, USA. Brown trout are one of several non-native fish species of management concern in this river reach, and understanding their natal sources and movement patterns may...
Authors
Michael K. Akland, Karin E. Limburg, Brian Healy, William Pine
Population growth of threatened Gulf Sturgeon may be limited by the frequency of adult episodic mortality events Population growth of threatened Gulf Sturgeon may be limited by the frequency of adult episodic mortality events
ObjectiveWe identified spatial and temporal variation in population trends for Gulf Sturgeon Acipenser desotoi (previously known as Acipenser oxyrinchus desotoi) across the species’ range to inform recovery strategies. We also assessed whether adult survival or recruitment more strongly influences population change.MethodsWe analyzed adult Gulf Sturgeon capture–recapture data from 1990...
Authors
Stephen Parker, William E. Pine, Brian Healy, James Hines
The value of information is context dependent: A demonstration of decision tools to address multispecies river temperature management under uncertainty The value of information is context dependent: A demonstration of decision tools to address multispecies river temperature management under uncertainty
Trade-offs among objectives in natural resource management can be exacerbated in altered ecosystems and when there is uncertainty in predicted management outcomes. Multi-criteria decision analysis and value of information (VOI) are underutilized decision tools that can assist fisheries managers in handling trade-offs and evaluating the importance of uncertainty. We demonstrate the use of...
Authors
Brian Healy, Michael Runge, Michael Beakes, Corey Phillis, Alexander Jensen, Joshua Israel
Translocation in a fragmented river provides demographic benefits for imperiled fishes Translocation in a fragmented river provides demographic benefits for imperiled fishes
Fragmentation isolates individuals and restricts access to valuable habitat with severe consequences for populations, such as reduced gene flow, disruption of recolonization dynamics, reduced resiliency to disturbance, and changes in aquatic community structure. Translocations to mitigate the effects of fragmentation and habitat loss are common, but few are rigorously evaluated...
Authors
Casey A. Pennock, Brian Healy, Matthew Bogaard, Mark McKinstry, Keith Gido, C. Cathcart, Brian Hines
Quantifying the contributions of tributaries to large-river fish populations through mark-recapture modeling Quantifying the contributions of tributaries to large-river fish populations through mark-recapture modeling
Tributaries may play a vital role in maintaining populations of large river fishes, although the specific contributions of tributaries toward recruitment of river-wide populations are not often understood. Tributaries may experience fewer cumulative anthropogenic impacts relative to mainstem rivers and may offer more natural conditions supportive of native fish populations, which may...
Authors
Brian Healy, Emily Omana Smith
Symposia summaries 2023 Symposia summaries 2023
No abstract available.
Authors
Brian Healy, Joshua Israel
Migration timing and tributary use of spawning flannelmouth sucker (Catostomus latipinnis) Migration timing and tributary use of spawning flannelmouth sucker (Catostomus latipinnis)
Spawning phenology and associated migrations of fishes are often regulated by factors such as temperature and stream discharge, but flow regulation of mainstem rivers coupled with climate change might disrupt these cues and affect fitness. Flannelmouth sucker (Catostomus latipinnis) persisting in heavily modified river networks are known to spawn in tributaries that might provide better...
Authors
Sophia Bonjour, Keith Gido, Mark McKinstry, Charles Cathcart, Matthew Bogaard, Maria Dzul, Brian Healy, Zachary Hooley-Underwood, David Rogowski, Charles Yackulic
Diverse portfolios: Investing in tributaries for restoration of large river fishes in the Anthropocene Diverse portfolios: Investing in tributaries for restoration of large river fishes in the Anthropocene
Rehabilitation of large Anthropocene rivers requires engagement of diverse stakeholders across a broad range of sociopolitical boundaries. Competing objectives often constrain options for ecological restoration of large rivers whereas fewer competing objectives may exist in a subset of tributaries. Further, tributaries contribute toward building a “portfolio” of river ecosystem assets...
Authors
Kristen Bouska, Brian Healy, Michael Moore, Corey Dunn, Jonathan Spurgeon, Craig Paukert
Impeding access to tributary spawning habitat and releasing experimental fall-timed floods increases brown trout immigration into a dam's tailwater Impeding access to tributary spawning habitat and releasing experimental fall-timed floods increases brown trout immigration into a dam's tailwater
River ecosystems have been altered by flow regulation and species introductions. Regulated flow regimes often include releases designed to benefit certain species or restore ecosystem processes, and invasive species suppression programs may include efforts to restrict access to spawning habitat. The impacts of these management interventions are often uncertain. Here, we assess hypotheses...
Authors
Brian Healy, Charles Yackulic, Robert Schelly
Exploring metapopulation-scale suppression alternatives for a global invader in a river network experiencing climate change Exploring metapopulation-scale suppression alternatives for a global invader in a river network experiencing climate change
Invasive species can dramatically alter ecosystems, but eradication is difficult, and suppression is expensive once they are established. Uncertainties in the potential for expansion and impacts by an invader can lead to delayed and inadequate suppression, allowing for establishment. Metapopulation viability models can aid in planning strategies to improve responses to invaders and...
Authors
Brian Healy, Phaedra E. Budy, Charles Yackulic, Brendan P. Murphy, Robert Schelly, Mark McKinstry
Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking...
Authors
Brian Healy, Phaedra E. Budy, Mary M. Conner, Emily Omana Smith
Non-USGS Publications**
Healy, B. D., J. F. Moore, and W. E. Pine. 2022. Monitoring and managing fishes that are invisible and keep moving around: Influences of an invasive species and environmental factors on capture probability. North American Journal of Fisheries Management 42:396-409. DOI: 10.1002/nafm.10755
Gilbert, E. I., W. H. Brandenburg, A. L. Barkalow, R. B. Kegerries, B. C. Albrecht, B. D. Healy, E. C. Omana Smith, J. R. Stolberg, M. C. McKinstry, and S. P. Platania. 2022. Systematic larval fish surveys and abiotic correlates characterize extant native fish reproductive success in the Colorado River, Grand Canyon, Arizona. The Southwestern Naturalist 66(1): 67-76. https://doi.org/10.1894/0038-4909-66.1.67
Healy, B. D., E. C. Omana Smith, M. Trammell, R. C. Schelly, C. B. Nelson. 2020. Establishment of a reproducing population of endangered Humpback Chub through translocations to a Colorado River tributary, Grand Canyon, Arizona. North American Journal of Fisheries Management 40: 278-292. DOI: 10.1002/nafm.10408
Kegerries, R. B., B. Albrecht, M. C. McKinstry, R. A. Valdez, R. J. Rogers, A. L. Barkalow, E. I. Gilbert, H. Mohn, B. Healy, and E. Omana Smith. 2020. Small-bodied fish surveys demonstrate native fish dominate over three hundred kilometers of the Colorado River through Grand Canyon, Arizona. Western North American Naturalist 80(2). https://scholarsarchive.byu.edu/wnan/vol80/iss2/2
Bair, R., B. W. Tobin, B. D. Healy, H. Childres, C. Spangenburger, E. Schenk. 2019. Modeling temperature regime and physical habitat impacts from restored streamflow. Environmental Management 63(6): 718-731. DOI: 10.1007/s00267-019-01157-8
Albrecht, B., H. E. Mohn, R. Kegerries, M. C. McKinstry, R. Rogers, T. Frances., B. Hines, J. Stolberg, D. Ryden, D. Elverud, B. Schleicher, K. Creighton, B. Healy, and B. Senger. 2017. Use of inflow areas in two Colorado River Basin reservoirs by endangered razorback sucker (Xyrauchen texanus). Western North American Naturalist 77(4): 500-514. DOI: 10.3398/064.077.0410
Kegerries, R. B., B. C. Albrecht, E. I. Gilbert, W. H. Brandenburg, A. L. Barkalow, M. C. McKinstry, H. E. Mohn, B. D. Healy, J. R. Stolberg, E. C. Omana Smith, C. B. Nelson, and R. J. Rogers. 2017. Occurrence and reproduction by Razorback Sucker (Xyrauchen texanus) in the Grand Canyon, Arizona. The Southwestern Naturalist 62(3):227- 232. DOI: 10.1894/0038-4909-62.3.227
Healy, B. D., and D. G. Lonzarich. 2000. Microhabitat use and behavior of overwintering juvenile coho salmon in a Lake Superior tributary. Transactions of the American Fisheries Society 129: 866-872. https://doi.org/10.1577/1548-8659(2000)129<0866:MUABOO>2.3.CO;2
**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
Rainbow Trout in the Colorado River, Grand Canyon
Rainbow trout are a desirable sport fish that have been introduced in many locations around the world, including the Colorado River. Although introductions of rainbow trout and other nonnative fishes provide recreational fishing opportunities, they can also pose threats to native fish populations. The Glen Canyon Dam Adaptive Management Program has tasked scientists and managers with identifying...
Multicriteria decision analysis scores for rapid delta smelt decision analysis Multicriteria decision analysis scores for rapid delta smelt decision analysis
These data were compiled to support water management decision-making by the U.S. Bureau of Reclamation and California Department of Water Resources related to the Central Valley Project (CVP) and State Water Project (SWP) operations in water year 2025. The objectives of the study were to use structured decision making to assess tradeoffs between multiple competing water needs and inform...
Brown trout movement data in Glen and Grand Canyons, Arizona, USA Brown trout movement data in Glen and Grand Canyons, Arizona, USA
These data were compiled to test hypotheses regarding drivers of movement of brown trout. Objectives of our study were to test whether the degree of movement varied in response to placement of a weir in Bright Angel Creek, fall timed flooding events, or simply seasonal changes. These data represent summarized capture histories of brown trout in terms of states based on physical locations...
Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking...
Authors
Brian Healy, Phaedra E. Budy, Mary M. Conner, Emily Omana Smith
Filter Total Items: 16
Rapid structured decision making for Hypomesus transpacificus (delta smelt) summer–fall freshwater outflow management Rapid structured decision making for Hypomesus transpacificus (delta smelt) summer–fall freshwater outflow management
Managers of the Central Valley Project (CVP) and State Water Projects (SWP) in California are confronted with difficult tradeoffs between water uses and associated values affected by water management decisions. These decisions involve altering the timing and magnitude of water releases from dams and reservoirs, which can affect habitats for economically important and Federally and State...
Authors
Brian Healy, Corey Phillis, Brian Mahardja, Cameron Koizumi, Catarina Pien, Nancy Parker, J. Conrad, Julie Ekstrom, Julie Leimbach, Rafael Silberblatt, Tom Fischer, Chase Ehlo
Mixed natal origins present management challenges for a non-native fish established throughout a modified river network Mixed natal origins present management challenges for a non-native fish established throughout a modified river network
Expansion of non-native brown trout (Salmo trutta) in the Colorado River below Glen Canyon Dam motivated reevaluation of suppression strategies to minimize potential impacts to native fishes in the Grand Canyon, Arizona, USA. Brown trout are one of several non-native fish species of management concern in this river reach, and understanding their natal sources and movement patterns may...
Authors
Michael K. Akland, Karin E. Limburg, Brian Healy, William Pine
Population growth of threatened Gulf Sturgeon may be limited by the frequency of adult episodic mortality events Population growth of threatened Gulf Sturgeon may be limited by the frequency of adult episodic mortality events
ObjectiveWe identified spatial and temporal variation in population trends for Gulf Sturgeon Acipenser desotoi (previously known as Acipenser oxyrinchus desotoi) across the species’ range to inform recovery strategies. We also assessed whether adult survival or recruitment more strongly influences population change.MethodsWe analyzed adult Gulf Sturgeon capture–recapture data from 1990...
Authors
Stephen Parker, William E. Pine, Brian Healy, James Hines
The value of information is context dependent: A demonstration of decision tools to address multispecies river temperature management under uncertainty The value of information is context dependent: A demonstration of decision tools to address multispecies river temperature management under uncertainty
Trade-offs among objectives in natural resource management can be exacerbated in altered ecosystems and when there is uncertainty in predicted management outcomes. Multi-criteria decision analysis and value of information (VOI) are underutilized decision tools that can assist fisheries managers in handling trade-offs and evaluating the importance of uncertainty. We demonstrate the use of...
Authors
Brian Healy, Michael Runge, Michael Beakes, Corey Phillis, Alexander Jensen, Joshua Israel
Translocation in a fragmented river provides demographic benefits for imperiled fishes Translocation in a fragmented river provides demographic benefits for imperiled fishes
Fragmentation isolates individuals and restricts access to valuable habitat with severe consequences for populations, such as reduced gene flow, disruption of recolonization dynamics, reduced resiliency to disturbance, and changes in aquatic community structure. Translocations to mitigate the effects of fragmentation and habitat loss are common, but few are rigorously evaluated...
Authors
Casey A. Pennock, Brian Healy, Matthew Bogaard, Mark McKinstry, Keith Gido, C. Cathcart, Brian Hines
Quantifying the contributions of tributaries to large-river fish populations through mark-recapture modeling Quantifying the contributions of tributaries to large-river fish populations through mark-recapture modeling
Tributaries may play a vital role in maintaining populations of large river fishes, although the specific contributions of tributaries toward recruitment of river-wide populations are not often understood. Tributaries may experience fewer cumulative anthropogenic impacts relative to mainstem rivers and may offer more natural conditions supportive of native fish populations, which may...
Authors
Brian Healy, Emily Omana Smith
Symposia summaries 2023 Symposia summaries 2023
No abstract available.
Authors
Brian Healy, Joshua Israel
Migration timing and tributary use of spawning flannelmouth sucker (Catostomus latipinnis) Migration timing and tributary use of spawning flannelmouth sucker (Catostomus latipinnis)
Spawning phenology and associated migrations of fishes are often regulated by factors such as temperature and stream discharge, but flow regulation of mainstem rivers coupled with climate change might disrupt these cues and affect fitness. Flannelmouth sucker (Catostomus latipinnis) persisting in heavily modified river networks are known to spawn in tributaries that might provide better...
Authors
Sophia Bonjour, Keith Gido, Mark McKinstry, Charles Cathcart, Matthew Bogaard, Maria Dzul, Brian Healy, Zachary Hooley-Underwood, David Rogowski, Charles Yackulic
Diverse portfolios: Investing in tributaries for restoration of large river fishes in the Anthropocene Diverse portfolios: Investing in tributaries for restoration of large river fishes in the Anthropocene
Rehabilitation of large Anthropocene rivers requires engagement of diverse stakeholders across a broad range of sociopolitical boundaries. Competing objectives often constrain options for ecological restoration of large rivers whereas fewer competing objectives may exist in a subset of tributaries. Further, tributaries contribute toward building a “portfolio” of river ecosystem assets...
Authors
Kristen Bouska, Brian Healy, Michael Moore, Corey Dunn, Jonathan Spurgeon, Craig Paukert
Impeding access to tributary spawning habitat and releasing experimental fall-timed floods increases brown trout immigration into a dam's tailwater Impeding access to tributary spawning habitat and releasing experimental fall-timed floods increases brown trout immigration into a dam's tailwater
River ecosystems have been altered by flow regulation and species introductions. Regulated flow regimes often include releases designed to benefit certain species or restore ecosystem processes, and invasive species suppression programs may include efforts to restrict access to spawning habitat. The impacts of these management interventions are often uncertain. Here, we assess hypotheses...
Authors
Brian Healy, Charles Yackulic, Robert Schelly
Exploring metapopulation-scale suppression alternatives for a global invader in a river network experiencing climate change Exploring metapopulation-scale suppression alternatives for a global invader in a river network experiencing climate change
Invasive species can dramatically alter ecosystems, but eradication is difficult, and suppression is expensive once they are established. Uncertainties in the potential for expansion and impacts by an invader can lead to delayed and inadequate suppression, allowing for establishment. Metapopulation viability models can aid in planning strategies to improve responses to invaders and...
Authors
Brian Healy, Phaedra E. Budy, Charles Yackulic, Brendan P. Murphy, Robert Schelly, Mark McKinstry
Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations
Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking...
Authors
Brian Healy, Phaedra E. Budy, Mary M. Conner, Emily Omana Smith
Non-USGS Publications**
Healy, B. D., J. F. Moore, and W. E. Pine. 2022. Monitoring and managing fishes that are invisible and keep moving around: Influences of an invasive species and environmental factors on capture probability. North American Journal of Fisheries Management 42:396-409. DOI: 10.1002/nafm.10755
Gilbert, E. I., W. H. Brandenburg, A. L. Barkalow, R. B. Kegerries, B. C. Albrecht, B. D. Healy, E. C. Omana Smith, J. R. Stolberg, M. C. McKinstry, and S. P. Platania. 2022. Systematic larval fish surveys and abiotic correlates characterize extant native fish reproductive success in the Colorado River, Grand Canyon, Arizona. The Southwestern Naturalist 66(1): 67-76. https://doi.org/10.1894/0038-4909-66.1.67
Healy, B. D., E. C. Omana Smith, M. Trammell, R. C. Schelly, C. B. Nelson. 2020. Establishment of a reproducing population of endangered Humpback Chub through translocations to a Colorado River tributary, Grand Canyon, Arizona. North American Journal of Fisheries Management 40: 278-292. DOI: 10.1002/nafm.10408
Kegerries, R. B., B. Albrecht, M. C. McKinstry, R. A. Valdez, R. J. Rogers, A. L. Barkalow, E. I. Gilbert, H. Mohn, B. Healy, and E. Omana Smith. 2020. Small-bodied fish surveys demonstrate native fish dominate over three hundred kilometers of the Colorado River through Grand Canyon, Arizona. Western North American Naturalist 80(2). https://scholarsarchive.byu.edu/wnan/vol80/iss2/2
Bair, R., B. W. Tobin, B. D. Healy, H. Childres, C. Spangenburger, E. Schenk. 2019. Modeling temperature regime and physical habitat impacts from restored streamflow. Environmental Management 63(6): 718-731. DOI: 10.1007/s00267-019-01157-8
Albrecht, B., H. E. Mohn, R. Kegerries, M. C. McKinstry, R. Rogers, T. Frances., B. Hines, J. Stolberg, D. Ryden, D. Elverud, B. Schleicher, K. Creighton, B. Healy, and B. Senger. 2017. Use of inflow areas in two Colorado River Basin reservoirs by endangered razorback sucker (Xyrauchen texanus). Western North American Naturalist 77(4): 500-514. DOI: 10.3398/064.077.0410
Kegerries, R. B., B. C. Albrecht, E. I. Gilbert, W. H. Brandenburg, A. L. Barkalow, M. C. McKinstry, H. E. Mohn, B. D. Healy, J. R. Stolberg, E. C. Omana Smith, C. B. Nelson, and R. J. Rogers. 2017. Occurrence and reproduction by Razorback Sucker (Xyrauchen texanus) in the Grand Canyon, Arizona. The Southwestern Naturalist 62(3):227- 232. DOI: 10.1894/0038-4909-62.3.227
Healy, B. D., and D. G. Lonzarich. 2000. Microhabitat use and behavior of overwintering juvenile coho salmon in a Lake Superior tributary. Transactions of the American Fisheries Society 129: 866-872. https://doi.org/10.1577/1548-8659(2000)129<0866:MUABOO>2.3.CO;2
**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.