Julie Yee
Dr. Julie Yee is a Research Statistician with the Western Ecological Research Center (WERC).
Since 1997, she has used statistics and biometry for WERC to quantitatively analyze and interpret a variety of aspects of wildlife and plant population dynamics, such as recruitment, growth, survival, and wildlife movement. Her research has been applied to study the effects of renewable energy, contaminants, fire, and other influences on wildlife populations and ecosystems. She is currently a PI at the Santa Cruz field station where she supervises continued work on sea otter and nearshore research.
RESEARCH INTERESTS
- Frequentist and Bayesian statistical analysis
- Survival analysis
- Population dynamics
- Mark-recapture
- State-space modeling
- Integrated population modeling
- High performance computing
EDUCATION
- Ph.D., 1997, Statistics with Emphasis in Biostatistics, University of California, Davis.
- Dissertation Title: Asymptotic Approximations to Bayesian Posterior Distributions in Survival Problems with Incomplete Data
- M.S., 1993, Statistics, University of California, Davis
- B.S., 1991, Mathematics, California Institute of Technology
Science and Products
Population Biology and Behavior of Sea Otters
WERC's sea otter researchers are developing and utilizing a variety of methodological and analytical tools to understand the causes of biological and ecological trends in sea otter populations, and to predict the ecological consequences of management practices on these populations and their ecosystems.
California Sea Otter Surveys and Research
WERC collaborates with other research scientists to conduct annual population surveys of the southern sea otter -- a federally listed threatened species. In coordination with the California Department of Fish and Game and other institutions, ongoing surveys and research continues to inform the southern sea otter recovery plan for the U.S. Fish and Wildlife Service, and contributes to our...
Pacific Nearshore Project
Sea otters are crucial indicators of the health of our nearshore waters and coastal resources, from kelp forests to fisheries. What clues does the sea otter's decline hold for our knowledge of ecosystem and global change? WERC's sea otter team and U.S. and Canadian researchers have teamed together to investigate. Relevance to USGS Missions: This research project has direct relevance for the...
California Sea Otter Stranding Network
The California Sea Otter Stranding Network is part of the USGS effort to monitor southern sea otters (Enhydra lutris nereis) and provide data to the U.S. Fish and Wildlife Service. WERC's sea otter team works with multiple institutions and partners to report, recover, and examine stranded sea otters. In addition, instructions on how to report a stranded sea otter are included in this webpage.
Santa Cruz Field Station
Scientists at the Santa Cruz Field Station study sea otters and seabirds in their environment. The USGS Western Ecological Research Center has two research missions based in the Santa Cruz region:
Methylmercury Effects on Birds: Bibliography and Dataset for the Development of Toxicity Reference Values for Injury Assessment
This data release contains three files. The first (Table S1 Bibliography Dataset) contains the entire bibliography for the 435 publications examined for potential inclusion into at least one of the meta-analyses for the effects of environmental mercury (Hg) on birds. For those 168 publications that were included in at least one meta-analysis, the worksheet titled Bibliography contains data describ
Demographic model inputs and code, catchment area population estimates, and counterfactual (CIU) estimates for population growth for 23 focal bird species.
Renewable energy production can kill birds, but little is known about how it affects avian populations. We assessed vulnerability of populations for 23 priority bird species killed at wind and solar facilities in California, USA.
Annual California Sea Otter Census-2018 Spring Census Summary
The spring 2018 mainland sea otter count began on April 26, and was completed by May 24, 2018. Overall viewing conditions this year were good and rounded off to the same conditions experienced during the 2017 spring census (View Score 2.4, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent). The surface canopies of kelp (Macrocystis sp.) were considered by most participants to be above nor
At-Sea Distribution and Abundance of Seabirds and Marine Mammals off Southern California GIS Resource Database: Aerial seabird and marine mammal surveys off southern California, 1999-2002
Background - Interest in developing alternative sources of renewable energy to reduce dependence on oil has increased in recent years. Some sources of renewable energy being considered will include power generation infrastructure and support activities located within continental shelf waters, and potentially within deeper waters off the U.S. Pacific coast and beyond state waters (i.e., outside thr
Historical methyl mercury in San Francisco Bay
San Francisco Bay, California is considered a mercury-impaired watershed. Elevated concentrations of mercury are found in water and sediment as well as fish and estuarine birds. Sources of mercury to the watershed since 1845 include sediment-associated mercury from mercury mining, mercury losses from gold amalgamation activities in mines of the Sierra Nevada, aerial deposition of mercury from gl
Filter Total Items: 55
Foraging ecology of southern sea otters at the northern range extent informs regional population dynamics
Sea otters Enhydra lutris are vital keystone predators throughout the North Pacific that were nearly extirpated during the maritime fur trade. Recovery of southern sea otters E. l. nereis has proceeded slowly, with much of their historical range remaining unoccupied, resulting in reduced ecosystem functioning. Numerous studies have used foraging metrics to assess the population status of southern
Authors
Sophia N. Lyon, Joseph A. Tomoleoni, Julie L. Yee, Jessica Fujii, Nicole M. Thometz
Modeling coupled dynamics of an empirical predator-prey system to predict top predator recovery
Limited data, time, and funding lead conservation managers to make difficult choices in managing species recovery. Coupled dynamical models are relied upon for decision support, but their application to empirical predator-prey systems has generally been restricted to small, tractable species. To broaden their use in conservation decision-making, we developed a model suitable for predicting the pop
Authors
Samantha N. M. Hamilton, M. T. Tinker, Joseph Jackson, Joseph A. Tomoleoni, Michael C. Kenner, Julie L. Yee, Tomoko Bell, Max C. N. Castorani, Benjamin H. Becker, Brent B. Hughes
Methylmercury effects on birds: A review, meta-analysis, and development of toxicity reference values for injury assessment based on tissue residues and diet
Birds are used as bioindicators of environmental mercury (Hg) contamination, and toxicity reference values are needed for injury assessments. We conducted a comprehensive review, summarized data from 168 studies, performed a series of Bayesian hierarchical meta-analyses, and developed new toxicity reference values for the effects of methylmercury (MeHg) on birds using a benchmark dose analysis fra
Authors
Josh T. Ackerman, Sarah H. Peterson, Mark P. Herzog, Julie L. Yee
Southern (California) sea otter population status and trends at San Nicolas Island, 2020–2023
The population of southern sea otters (Enhydra lutris nereis) at San Nicolas Island, California, has been monitored annually since the translocation of 140 southern sea otters to the island was completed in 1990. Monitoring efforts have varied in frequency and type across years. In 2017, the U.S. Navy and the U.S. Fish and Wildlife Service initiated a southern sea otter monitoring and research pla
Authors
Julie L. Yee, Joseph A. Tomoleoni, Michael C. Kenner, Jessica A. Fujii, Gena B. Bentall, Michelle M. Staedler, Brian B. Hatfield
Gene expression and wildlife health: Varied interpretations based on perspective
We evaluated wildlife population health from the perspective of statistical means vs. variances. We outlined the choices necessary to provide the framework for our study. These consisted of spatial and temporal boundaries (e.g., choice of sentinel species, populations, time frame), measurement techniques (molecular to population level), and appropriate statistical analyses. We chose to assess the
Authors
Lizabeth Bowen, Julie L. Yee, James L. Bodkin, Shannon C. Waters, Michael J. Murray, Heather Coletti, Brenda E. Ballachey, Daniel Monson, A. Keith Miles
Black Abalone surveys at Naval Base Ventura County, San Nicolas Island, California—2021, annual report
The U.S. Geological Survey monitors a suite of intertidal black abalone sites at San Nicolas Island, California, in cooperation with the U.S. Navy, which owns the island. The nine rocky intertidal sites were established in 1980 to study the potential effect of translocated sea otters on the intertidal black abalone population at the island. The sites were monitored from 1981 to 1997, usually annua
Authors
Michael C. Kenner, Julie L. Yee
Spatial effects in relation to reproductive performance of Common Murres (Uria aalge) at a re-established colony
A main goal of seabird colony restoration is for the colony to become self-sustaining. To do so, elevated rates must be attained in (1) reproductive success and (2) recruitment by immigrants and birds produced at the colony. Thus, an understanding of the factors affecting reproductive success and recruitment at restoration sites is vital. We examined how spatial features at the colony level affect
Authors
Gerard J. McChesney, Julie L. Yee, Michael W. Parker, William M. Perry, Harry R. Carter, Richard T. Golightly, Stephen W. Kress
Vulnerability of avian populations to renewable energy production
Renewable energy production can kill individual birds, but little is known about how it affects avian populations. We assessed the vulnerability of populations for 23 priority bird species killed at wind and solar facilities in California, USA. Bayesian hierarchical models suggested that 48% of these species were vulnerable to population-level effects from added fatalities caused by renewables and
Authors
Tara Conkling, Hannah B. Vander Zanden, Taber D Allison, James E. Diffendorfer, Thomas V Dietsch, A. Duerr, Amy L Fesnock, Rebecca R. Hernandez, S. R. Loss, David M. Nelson, Peter M. Sanzenbacher, Julie L. Yee, Todd E. Katzner
Kelp-forest dynamics controlled by substrate complexity
The factors that determine why ecosystems exhibit abrupt shifts in state are of paramount importance for management, conservation, and restoration efforts. Kelp forests are emblematic of such abruptly shifting ecosystems, transitioning from kelp-dominated to urchin-dominated states around the world with increasing frequency, yet the underlying processes and mechanisms that control their dynamics r
Authors
Zachary Randell, Michael C. Kenner, Joseph A. Tomoleoni, Julie L. Yee, Mark Novak
Sea otters in a California estuary: Detecting temporal and spatial dynamics with volunteer monitoring
Volunteer monitoring can support conservation of imperiled wildlife, by providing higher resolution data in space and time than those available from professional scientists. However, concerns have been raised that data collected by amateurs are inaccurate or inconsistent and thus do not allow for robust detection of spatial or temporal trends. We evaluated the rigor and value of volunteer monitori
Authors
Ron Eby, Susan Rosso, John Copriviza, Robert Scoles, Yohn Gideon, Joseph Mancino, Karl A. Mayer, Julie L. Yee, Kerstin Wasson
Development of demographic models to analyze populations with multi-year data—Using Agassiz’s Desert Tortoise (Gopherus agassizii) as a case study
We developed a model for analyzing multi-year demographic data for long-lived animals and used data from a population of Agassiz’s desert tortoise (Gopherus agassizii) at the Desert Tortoise Research Natural Area in the western Mojave Desert of California as a case study. The study area was 7.77 square kilometers and included two locations: inside and outside the fenced boundary. The wildlife-perm
Authors
Kristin H. Berry, Julie L. Yee
An integrated population model for southern sea otters
Southern sea otters (Enhydra lutris nereis) have recovered slowly from their near extinction a century ago, and their continued recovery has been challenged by multiple natural and anthropogenic factors. Development of an integrated population model (IPM) for southern sea otters has been identified as a management priority, to help in evaluating the relative impacts of known threats and guide best
Authors
M. Tim Tinker, Lilian P. Carswell, Joseph A. Tomoleoni, Brian B. Hatfield, Michael D. Harris, Melissa A. Miller, Megan E. Moriarty, Christine K. Johnson, Colleen Young, Laird A. Henkel, Michelle M. Staedler, A. Keith Miles, Julie L. Yee
Methylmercury Effects on Birds: Percent Injury Tool
Welcome to The Bird Mercury Tool website. Please follow the guidance below to download the tool and user guide.
The Bird Mercury Tool: Estimating Methylmercury Injury to Birds can be used by practitioners to help interpret injury to birds caused by methylmercury concentrations in bird tissues or diet.
The dataset, statistical models, and assumptions used within this tool have been published separa
Science and Products
Population Biology and Behavior of Sea Otters
WERC's sea otter researchers are developing and utilizing a variety of methodological and analytical tools to understand the causes of biological and ecological trends in sea otter populations, and to predict the ecological consequences of management practices on these populations and their ecosystems.
California Sea Otter Surveys and Research
WERC collaborates with other research scientists to conduct annual population surveys of the southern sea otter -- a federally listed threatened species. In coordination with the California Department of Fish and Game and other institutions, ongoing surveys and research continues to inform the southern sea otter recovery plan for the U.S. Fish and Wildlife Service, and contributes to our...
Pacific Nearshore Project
Sea otters are crucial indicators of the health of our nearshore waters and coastal resources, from kelp forests to fisheries. What clues does the sea otter's decline hold for our knowledge of ecosystem and global change? WERC's sea otter team and U.S. and Canadian researchers have teamed together to investigate. Relevance to USGS Missions: This research project has direct relevance for the...
California Sea Otter Stranding Network
The California Sea Otter Stranding Network is part of the USGS effort to monitor southern sea otters (Enhydra lutris nereis) and provide data to the U.S. Fish and Wildlife Service. WERC's sea otter team works with multiple institutions and partners to report, recover, and examine stranded sea otters. In addition, instructions on how to report a stranded sea otter are included in this webpage.
Santa Cruz Field Station
Scientists at the Santa Cruz Field Station study sea otters and seabirds in their environment. The USGS Western Ecological Research Center has two research missions based in the Santa Cruz region:
Methylmercury Effects on Birds: Bibliography and Dataset for the Development of Toxicity Reference Values for Injury Assessment
This data release contains three files. The first (Table S1 Bibliography Dataset) contains the entire bibliography for the 435 publications examined for potential inclusion into at least one of the meta-analyses for the effects of environmental mercury (Hg) on birds. For those 168 publications that were included in at least one meta-analysis, the worksheet titled Bibliography contains data describ
Demographic model inputs and code, catchment area population estimates, and counterfactual (CIU) estimates for population growth for 23 focal bird species.
Renewable energy production can kill birds, but little is known about how it affects avian populations. We assessed vulnerability of populations for 23 priority bird species killed at wind and solar facilities in California, USA.
Annual California Sea Otter Census-2018 Spring Census Summary
The spring 2018 mainland sea otter count began on April 26, and was completed by May 24, 2018. Overall viewing conditions this year were good and rounded off to the same conditions experienced during the 2017 spring census (View Score 2.4, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent). The surface canopies of kelp (Macrocystis sp.) were considered by most participants to be above nor
At-Sea Distribution and Abundance of Seabirds and Marine Mammals off Southern California GIS Resource Database: Aerial seabird and marine mammal surveys off southern California, 1999-2002
Background - Interest in developing alternative sources of renewable energy to reduce dependence on oil has increased in recent years. Some sources of renewable energy being considered will include power generation infrastructure and support activities located within continental shelf waters, and potentially within deeper waters off the U.S. Pacific coast and beyond state waters (i.e., outside thr
Historical methyl mercury in San Francisco Bay
San Francisco Bay, California is considered a mercury-impaired watershed. Elevated concentrations of mercury are found in water and sediment as well as fish and estuarine birds. Sources of mercury to the watershed since 1845 include sediment-associated mercury from mercury mining, mercury losses from gold amalgamation activities in mines of the Sierra Nevada, aerial deposition of mercury from gl
Filter Total Items: 55
Foraging ecology of southern sea otters at the northern range extent informs regional population dynamics
Sea otters Enhydra lutris are vital keystone predators throughout the North Pacific that were nearly extirpated during the maritime fur trade. Recovery of southern sea otters E. l. nereis has proceeded slowly, with much of their historical range remaining unoccupied, resulting in reduced ecosystem functioning. Numerous studies have used foraging metrics to assess the population status of southern
Authors
Sophia N. Lyon, Joseph A. Tomoleoni, Julie L. Yee, Jessica Fujii, Nicole M. Thometz
Modeling coupled dynamics of an empirical predator-prey system to predict top predator recovery
Limited data, time, and funding lead conservation managers to make difficult choices in managing species recovery. Coupled dynamical models are relied upon for decision support, but their application to empirical predator-prey systems has generally been restricted to small, tractable species. To broaden their use in conservation decision-making, we developed a model suitable for predicting the pop
Authors
Samantha N. M. Hamilton, M. T. Tinker, Joseph Jackson, Joseph A. Tomoleoni, Michael C. Kenner, Julie L. Yee, Tomoko Bell, Max C. N. Castorani, Benjamin H. Becker, Brent B. Hughes
Methylmercury effects on birds: A review, meta-analysis, and development of toxicity reference values for injury assessment based on tissue residues and diet
Birds are used as bioindicators of environmental mercury (Hg) contamination, and toxicity reference values are needed for injury assessments. We conducted a comprehensive review, summarized data from 168 studies, performed a series of Bayesian hierarchical meta-analyses, and developed new toxicity reference values for the effects of methylmercury (MeHg) on birds using a benchmark dose analysis fra
Authors
Josh T. Ackerman, Sarah H. Peterson, Mark P. Herzog, Julie L. Yee
Southern (California) sea otter population status and trends at San Nicolas Island, 2020–2023
The population of southern sea otters (Enhydra lutris nereis) at San Nicolas Island, California, has been monitored annually since the translocation of 140 southern sea otters to the island was completed in 1990. Monitoring efforts have varied in frequency and type across years. In 2017, the U.S. Navy and the U.S. Fish and Wildlife Service initiated a southern sea otter monitoring and research pla
Authors
Julie L. Yee, Joseph A. Tomoleoni, Michael C. Kenner, Jessica A. Fujii, Gena B. Bentall, Michelle M. Staedler, Brian B. Hatfield
Gene expression and wildlife health: Varied interpretations based on perspective
We evaluated wildlife population health from the perspective of statistical means vs. variances. We outlined the choices necessary to provide the framework for our study. These consisted of spatial and temporal boundaries (e.g., choice of sentinel species, populations, time frame), measurement techniques (molecular to population level), and appropriate statistical analyses. We chose to assess the
Authors
Lizabeth Bowen, Julie L. Yee, James L. Bodkin, Shannon C. Waters, Michael J. Murray, Heather Coletti, Brenda E. Ballachey, Daniel Monson, A. Keith Miles
Black Abalone surveys at Naval Base Ventura County, San Nicolas Island, California—2021, annual report
The U.S. Geological Survey monitors a suite of intertidal black abalone sites at San Nicolas Island, California, in cooperation with the U.S. Navy, which owns the island. The nine rocky intertidal sites were established in 1980 to study the potential effect of translocated sea otters on the intertidal black abalone population at the island. The sites were monitored from 1981 to 1997, usually annua
Authors
Michael C. Kenner, Julie L. Yee
Spatial effects in relation to reproductive performance of Common Murres (Uria aalge) at a re-established colony
A main goal of seabird colony restoration is for the colony to become self-sustaining. To do so, elevated rates must be attained in (1) reproductive success and (2) recruitment by immigrants and birds produced at the colony. Thus, an understanding of the factors affecting reproductive success and recruitment at restoration sites is vital. We examined how spatial features at the colony level affect
Authors
Gerard J. McChesney, Julie L. Yee, Michael W. Parker, William M. Perry, Harry R. Carter, Richard T. Golightly, Stephen W. Kress
Vulnerability of avian populations to renewable energy production
Renewable energy production can kill individual birds, but little is known about how it affects avian populations. We assessed the vulnerability of populations for 23 priority bird species killed at wind and solar facilities in California, USA. Bayesian hierarchical models suggested that 48% of these species were vulnerable to population-level effects from added fatalities caused by renewables and
Authors
Tara Conkling, Hannah B. Vander Zanden, Taber D Allison, James E. Diffendorfer, Thomas V Dietsch, A. Duerr, Amy L Fesnock, Rebecca R. Hernandez, S. R. Loss, David M. Nelson, Peter M. Sanzenbacher, Julie L. Yee, Todd E. Katzner
Kelp-forest dynamics controlled by substrate complexity
The factors that determine why ecosystems exhibit abrupt shifts in state are of paramount importance for management, conservation, and restoration efforts. Kelp forests are emblematic of such abruptly shifting ecosystems, transitioning from kelp-dominated to urchin-dominated states around the world with increasing frequency, yet the underlying processes and mechanisms that control their dynamics r
Authors
Zachary Randell, Michael C. Kenner, Joseph A. Tomoleoni, Julie L. Yee, Mark Novak
Sea otters in a California estuary: Detecting temporal and spatial dynamics with volunteer monitoring
Volunteer monitoring can support conservation of imperiled wildlife, by providing higher resolution data in space and time than those available from professional scientists. However, concerns have been raised that data collected by amateurs are inaccurate or inconsistent and thus do not allow for robust detection of spatial or temporal trends. We evaluated the rigor and value of volunteer monitori
Authors
Ron Eby, Susan Rosso, John Copriviza, Robert Scoles, Yohn Gideon, Joseph Mancino, Karl A. Mayer, Julie L. Yee, Kerstin Wasson
Development of demographic models to analyze populations with multi-year data—Using Agassiz’s Desert Tortoise (Gopherus agassizii) as a case study
We developed a model for analyzing multi-year demographic data for long-lived animals and used data from a population of Agassiz’s desert tortoise (Gopherus agassizii) at the Desert Tortoise Research Natural Area in the western Mojave Desert of California as a case study. The study area was 7.77 square kilometers and included two locations: inside and outside the fenced boundary. The wildlife-perm
Authors
Kristin H. Berry, Julie L. Yee
An integrated population model for southern sea otters
Southern sea otters (Enhydra lutris nereis) have recovered slowly from their near extinction a century ago, and their continued recovery has been challenged by multiple natural and anthropogenic factors. Development of an integrated population model (IPM) for southern sea otters has been identified as a management priority, to help in evaluating the relative impacts of known threats and guide best
Authors
M. Tim Tinker, Lilian P. Carswell, Joseph A. Tomoleoni, Brian B. Hatfield, Michael D. Harris, Melissa A. Miller, Megan E. Moriarty, Christine K. Johnson, Colleen Young, Laird A. Henkel, Michelle M. Staedler, A. Keith Miles, Julie L. Yee
Methylmercury Effects on Birds: Percent Injury Tool
Welcome to The Bird Mercury Tool website. Please follow the guidance below to download the tool and user guide.
The Bird Mercury Tool: Estimating Methylmercury Injury to Birds can be used by practitioners to help interpret injury to birds caused by methylmercury concentrations in bird tissues or diet.
The dataset, statistical models, and assumptions used within this tool have been published separa