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Research Projects

Native American Fish Weir - Etowah River, GA 


  • Principles of conservation biology and ecology

  • Capture-mark-recapture and state-based modeling

  • Dynamic occupancy (presence/absence) modeling

  • Spatial habitat analysis and remote sensing

  • Ecological forecasting and scenario planning

  • Facilitation, elicitation, and group dynamics

  • Inventory and monitoring planning and design

  • Survey protocol development and implementation

  • Decision analysis (structured decision-making)

  • Risk, uncertainty, and sensitivity analysis

  • Bayesian statistics and adaptive management

  • Project management, planning and design


Remote Sensing to Monitor Salt Marsh Vegetation Communities (Management Objectives) on Refuges

Bush N., R. Katz. In Prep. The Utility of Remote Sensing Data and Machine Learning for Monitoring Salt Marsh Management Objectives on North Atlantic-Appalachian Region National Wildlife Refuges. To be submitted to Wetlands or Remote Sensing.
In progress...
Supporting Structured Decision Making Community of Practice - Book Club

Over the last decade, there is an increasing interest and need for improving collaborative decision-making processes across many aspects of conservation organizations. In an effort to increase skills and tools available for problem solving based in decision theory, I have helped lead a series of book clubs for the structured decision making community of practice, which has included the following:

Supporting USFWS Species Status Assessments


The Species Status Assessment (SSA) framework was developed as part of the ongoing effort to improve implementation of the Endangered Species Act (ESA) and enhance conservation success. An SSA is a focused, repeatable, and rigorous assessment of a species' ability to maintain self-sustaining populations over time. This assessment is based on the best available scientific and commercial information regarding life history, biology, and consideration of current and future vulnerabilities. The result is a single document that delivers foundational science for informing all ESA decisions, including listing determinations, consultations, grant allocations, permitting, and recovery planning. [SSA Fact Sheet]

I consult a range of staff on developing various aspects of SSAs. For example:

  • Facilitating a workshop focused on developing a range wide conservation strategy for Gopher Frog (foundation for SSA) [link TBD]

  • Synthesizing information to inform the current condition (resiliency) for northern population of Bog Turtle [link]

  • Utilizing concepts of 3R's (resiliency, redundancy, representation) and recovery criteria to inform refuge-scale management objectives and monitoring (e.g. piping plover, red knot, seabeach amaranth, northeastern tiger beetle, swamp pink) [link TBD]

Developing Refuge Management Objectives and Inventory and Monitoring Plans 
This project focused on assisting refuges with the development of management objectives and inventory and monitoring plans (IMP) to ensure survey information is used to inform management decisions. Selecting field surveys to conduct is challenging because there are many different reasons for particular surveys or groups of surveys (e.g. baseline inventory (status), trend monitoring, monitoring to inform management (effectiveness monitoring, threshold/trigger monitoring), reducing system uncertainty, and supporting research and management needs of partners). To aid in the decision of which surveys to conduct,  we used elements of decision theory to develop objective hierarchies (fundamental and means objectives) with associated SMART objective statements representing measurable of success (performance metrics). These objectives and attributes set the stage for developing and evaluating management actions and monitoring needs.  
By working across four major ecosystems simultaneously (terrestrial, salt marsh, beach, and freshwater wetlands), refuges identified five overarching fundamental objectives, which tier from refuge policy, mandates, and refuge purposes. For each fundamental objective, a set of measurable attributes were developed with subject matter experts using the SMART framework (specific, measurable, achievable, results-oriented, time-specific). Attributes may include both population, habitat, and abiotic factors. These attributes were used as a foundation for selecting surveys that understand how close or far each refuge is to achieving management objectives and for monitoring effectiveness of actions toward these objectives. The next phase of support will include protocol development, which will consider the effectiveness of management strategies and identifying major uncertainties that must be resolved to revised actions. 

Fundamental objectives for each ecosystem:

  • Maintain the ecosystem over time

  • Support migratory bird populations

  • Support recovery of federally endangered and threatened species

  • Support refuge priority resources of concern

  • Maintain biological diversity and ecological integrity

Citations: In progress

Regional Protocol Framework for the Inventory of Invasive Plants


This regional protocol provides a framework for quantifying the baseline spatial distribution and infestation states of target invasive plant species for the Department of Interior North Atlantic-Appalachian Region (IR-1), U.S. Fish and Wildlife Service National Wildlife Refuge System (NWRS). A primary purpose of the protocol is to standardize a rapid, spatial approach for mapping invasive plant species with a regional data management system. The techniques described herein involve identifying the appropriate sampling frame (e.g. habitats or management areas), creating a standardized grid for surveying, and using Environmental Systems Research Institute (Esri) ArcGIS Online (AGOL) with Collector on an iOS device to collect data using a rapid area search. The framework recommends using the Invasive Plant Inventory and Early Detection Prioritization Tool in conjunction with the Invasive Plant Management Prioritization Tool to identity areas and invasive plants for inventory before implementing this protocol. This protocol also provides guidance for recording management actions that are implemented as a result of survey results. The framework allows data to be compiled at the refuge and regional level to assess the extent of the invasive plant problem, and to aid in the develop management targets and strategies, leading to the development of additional high priority surveys (i.e. state-based monitoring or management effectiveness monitoring).

Bush N., R. Katz, L. Eaton, K. Vagos, L. Mowbray, and K. Sturm. 2021. Regional Protocol Framework for the Inventory Invasive Plants. Version 1.0. Department of Interior North Atlantic-Appalachian Region, U.S. Fish and Wildlife Service, National Wildlife Refuge System, Hadley, MA. [link]
Regional Protocol Framework for the Inventory and Monitoring of Breeding Atlantic Coast Piping Plovers
The Atlantic Coast Piping Plover (Charadrius melodus) population was federally-listed as threatened in 1986 and comprises fewer than 2,000 breeding pairs, which nest on beaches from North Carolina to Maine (Northeast Region 5 and Region 4). U.S. Fish and Wildlife Service’s (USFWS) species recovery plan aims to increase population sizes by maximizing recruitment and adult survival. Breeding pairs and fledglings on beaches are threatened by predation and human disturbance, and natural weather events (overwash) can reduce the likelihood of nesting success. Monitoring data has been collected by individual partners and synthesized at the state and recovery unit level to inform decisions. However, monitoring protocols are not standardized across the range, leading to potentially inaccurate and biased estimates of success and management effectiveness. We are developing a regional protocol framework, supported by the NWRS Inventory and Monitoring Initiative, to increase efficient data collection (Plover Inventory and Productivity Library; PIPLweb) for all partners (federal, state, and non-governmental agencies). The web application, which can also accept data from exiting databases (NestStory, Survey123), will allow users to store, share, and analyze their data to inform annual and seasonal decisions (i.e., next exclosures using PiperEx) and ultimately recovery success.
Collaborators: U.S. Fish and Wildlife Service National Wildlife Refuge System, Ecological Services, and Migratory Birds, U.S. Geological Survey Wetland and Aquatic Research Center, SUNY College of Environmental Science and Forestry,

Katz R., and E. King. 2020. 2019 Regional Annual Report: Regional Protocol for the Inventory and Monitoring of Atlantic Coast Piping Plovers. U.S. Fish and Wildlife Service. Hadley, MA. [link]

King E., R.A. Katz, K.E. Iaquinto, K. Suir, M.J. Baldwin, A. Hecht. 2019. National Protocol Framework for the Inventory and Monitoring of Piping Plover Atlantic Coast Breeding Populations. Version 1.0. US Fish and Wildlife Service Northeast Regional Office, Hadley, MA. [link]

Stantial M., R. Katz, J. Cohen, *K. Amaral, J. Denoncour, A. Hecht, K. Hojnacki, K. Hunt, K. O'Brien, N. Pau, J. Regosin, C. Spiegel, L. Tudor, D. Tyre (*listed alphabetically). 2018. Structured Decision Making for Predator Removal to Benefit Piping Plovers and Other Beach Nesting Birds Least Terns. In Guidance and Best Practices for Coordinated Predation Management to Benefit Temperate Breeding Shorebirds in the Atlantic Flyway. U.S. Fish and Wildlife Service Report, 32 pg. [link]

Vernal Pool Management and Monitoring on National Wildlife Refuges


Studies by U.S. Geological Survey (USGS) suggest that occupancy of two vernal pool obligates (i.e., spotted salamander and wood frog), are declining across the northeastern U.S. Over the past 10-years, species occupancy on many National Wildlife Refuges (NWR) have demonstrated slow declines, with only a few NWRs  showing stable or increasing populations. We used a structured decision-making process to prototype a management framework and identify information needs for three NWRs: Umbagog NWR, Eastern Mass NWR Complex, and Canaan Valley NWR. The steps of the SDM process (PrOACT) can be summarized as 1) framing the problem, 2) clarifying the management objectives, 3) developing alternative actions and strategies, 4) predicting consequences of actions in terms of the objectives, 5) evaluating trade-offs, and 6) making decisions and taking action. NWR planning policies (Comprehensive Conservation Plan, Habitat Management Plan, and Inventory and Monitoring Plan) provide a framework for setting biological objectives for vernal pool obligates (e.g. Resources of Concern), as well as developing management strategies and monitoring elements that process toward biological objectives and to evaluate management effectiveness over time. We preliminary diagnosed why the problem was difficult from a decision analysis perspective, identified limiting factors, and alternative strategies for each NWR, as well as evaluated common challenges and impediments to decision-making across NWRs.


R. Katz, A. Brand, N. Bush ,C. Davis, L. Eaton, J. Flemming, S. Flint, E. Grant, J. Horan, E. King, S. Koch, K. Lantz, R. Longenecker, B. Mosher, A. Rizzo, D. Washington, T. Wilson, D. Zimmerman (*listed alphabetically). 2019. Challenges and Opportunities for Vernal Pool Management in Northeastern National Wildlife Refuges. U.S. Fish and Wildlife Service Report, 39 pg. [link]
Conservation benefits of road-based citizen science to pond-breeding amphibians


Road‐side amphibian citizen science programs bring together volunteers to collect scientific data and mitigate population declines by reducing road mortality of pond‐breeding amphibians. Despite the international popularity of these movement‐based, road‐side conservation efforts (i.e., ‘big nights’, ‘bucket brigades’ and ‘toad patrols’), direct benefits to conservation have rarely been quantified or evaluated. We used a population simulation to evaluate how volunteer intensity, frequency and distribution influence three conservation outcomes of the spotted salamander (Ambystoma maculatum), a focal species of 'big night' events in the northeastern US. Our sensitivity analysis supported the expectation that salamander populations are primarily recruitment‐driven. Conservation outcomes were highest when volunteers focused on metamorph out‐migration metamorphs as opposed to adult in‐migration, which is contrary to the current timing of such volunteer events. Volunteers during the first adult in‐migration (current strategy) had a relatively small effect compared to most other strategies. Small population sizes resulted in a negligible effect of volunteer intensity. Although citizen science‐focused conservation actions could directly benefit declining populations, additional conservation measures are needed to halt or reverse local amphibian declines. This study demonstrates a need to evaluate the effectiveness of focusing citizen science mitigation efforts on the metamorph stage, as opposed to the adult stage. This may be challenging, compared to other management actions such as road‐crossing infrastructure. Current amphibian citizen science programs will be challenged to balance implementing evidence‐based conservation measures on the most limiting life stage, while retaining social and community benefits for volunteers.

Based on the results of the simulation study, we are conducting surveys of citizen scientists who conduct bucket brigades to better understand motivations in an effort to evaluate potential for behavior change to maximize preferred outcomes of participants. 
Funding: USGS Patuxent Wildlife Research Center, Northeast Amphibian Research and Monitoring Initiative
Sterrett, S.C., R.A. Katz , W.R. Fields, and E.H. Campbell Grant. 2019. The contribution of road-based citizen science  to the conservation of pond-breeding amphibians. Journal of Applied Ecology 56(4): 988-995[link]
Evaluating stream crossing removal strategies 
Patuxent Research Refuge (PRR) is located within the Little Patuxent River, Upper Patuxent River and Anacostia River Watersheds and contains over 71 road-stream crossing. Improperly sized crossings can alter hydrologic regimes, reduce aquatic connectivity, and contribute fish and mussel declines. Additionally, poor infrastructure can affect sediment dynamics and increase the risk of flooding, potentially impacting public safety. PRR's Comprehensive Conservation Plan outlines the need to address road crossings, thus the refuge aimed to identify several crossings to restore (repair or replace) within the next 5 years to achieve this goal. The decision of which crossings to select was not obvious because the refuge had 1) multiple objectives to balancing, including biological benefits, impacts to existing operations, and public safety, and 2) many options (combinations of culverts) to evaluate and with limited data available make precise predictions. PRR developed 5 alternative strategies, which were then evaluated using a multi-criteria decision analysis approach. Despite variation in the relative importance of various objectives, the best performing alternative for every staff member was the "Close to Mainstem with Large Upstream Network" strategy which included 6 crossings. This alternative was predicted to increase fish spawning and juvenile habitat and result in reduced number of crossings at risk of flooding. Using a transparent decision framework allowed stakeholders to discuss goals, hypotheses, and assumptions and collaborate to create solutions to address aquatic connectivity, which is a high priority across USFWS Northeast Region. 
Adams T., J. Bourne, J. Devers, R. Katz, B. Knudson, R. Longenecker, and S. Spencer (listed alphabetically). 2018. Evaluating Stream Crossings for Restoration. Patuxent Research Refuge Road-Stream Crossing Prioritization FWS Report, 26 pg. Patuxent Wildlife Research Refuge, MD. [link]
Evaluating costs and benefits of removing freshwater impoundments 
Erie National Wildlife Refuge is located in PA and contains 16 freshwater impoundments in its Sugar Lake Division. As part of the Comprehensive Conservation Planning process (a 15-year plan), the Refuge was tasked to identify several impoundments for removal and restoration. Individual impoundments varied in terms of their value for wildlife, recreational opportunities, feasibility and partner support. We used a structured decision-making approach and multi-criteria decision analysis to identify which combination of impoundments could be removed to balance diverse refuge goals. Refuge staff developed six fundamental objectives that represented ecological goals (aquatic connectivity, brook trout populations, waterbird assemblages) and recreational values (wildlife viewing, trail access, fishing opportunities), 11 alternatives (single or groups of impoundments), and used a consequence table to clearly understand trade-offs associated with each alternative. The SDM process provided a transparent selection method that explicitly incorporated refuge staff’s preferences for each objective.

Althouse M., R. Katz, R. Longnecker, V. Muller, and T. Roster (listed alphabetically). 2017. Freshwater impoundment removal decision analysis, Erie NWR Comprehensive Conservation Plan Appendix H. U.S. Fish and Wildlife Report, 15 pg. [link]

Evaluating strategies for mitigating Bsal threat to US salamander populations during pre-invasion, invasion, and endemic stages


The recently identified pathogenic chytrid fungus, Batrachochytrium salamandrivorans (Bsal), poses a severe threat to the distribution and abundance of salamanders within the United States  and Europe. Development of a response strategy for the potential, and likely, invasion of Bsal into the United States is crucial to protect global salamander biodiversity. Given that the introduction of Bsal into the United States is highly probable, if not inevitable, research and managemet agencies are interested developing immediate short-term and long-term intervention strategies to prevent Bsal establishment and biodiversity decline. This research focuses on developing a flexible decision framework for management agencies to evaluate proactive, reactive, and restorative managment approaches and the potential costs of waiting to implement Bsal management strategies. Additionally, we aim to identify key research needs (hypotheses related to pathogen dispersal, population responses, and treatement effectiveness) using value of information theory to help guide research efforts on this emerging fungal pathogen.

Funding: USGS Patuxent Wildlife Research Center, Amphibian Research and Monitoring Initiative (ARMI), USGS Powell Center, USGS National Wildlife Health Center. These publications were developed as part of the Bsal Task Force's Decision Support Working Group.
Campbell-Grant E.H., E.L. Muths, R.A. Katz, S. Canessa, M.J. Adams et al. 2017. Even with forewarning, challenge remain in developing a proactive response to emerging diseases. Frontiers in Ecology and the Environment 15(4): 214-221. [link] 
Russell R.E., R.A. Katz, K.L.D. Richgels, D.P. Walsh, and E.H. Campbell-Grant. 2017A framework for modeling emerging disease to inform management. Emerging Infectious Diseases 23(1): 1-6. [link]
Campbell-Grant E.H., E.L. Muths, R.A. Katz, S. Canessa, M.J. Adams et al. Salamander chytrid fungus (Batrachochytrium salamandrivorans) in the United States—Developing research, monitoring, and management strategies. 2016. USGS Open-File Report 2015-1233. [link]

Related: Harris, M.C., Pearce, J.M., Prosser, D.J., White, C.L., Miles, A.K., Sleeman, J.M., Brand, C.J., Cronin, J.P., De La Cruz, S., Densmore, C.L., Doyle, T.W., Dusek, R.J., Fleskes, J.P., Flint, P.L., Guala, G.F., Hall, J.S., Hubbard, L.E., Hunt, R.J., Ip, H.S., Katz, R.A., Laurent, K.W., Miller, M.P., Munn, M.D., Ramey, A.M., Richards, K.D., Russell, R.E., Stokdyk, J.P., Takekawa, J.Y., and Walsh, D.P., 2016, U.S. Geological Survey science strategy for highly pathogenic avian influenza in wildlife and the environment (2016–2020): U.S. Geological Survey Open-File Report 2016–1121, 38 p. [link]

Spatial ecology of Shoal Bass using a habitat use-availablity framework

Shoal Bass (Micropterus cataractae) are fluvial specialists endemic to the Apalachicola-Chattahoochee- Flint River Basin and in decline throughout their native range. Effective conservation requires a comprehensive understanding of the migratory behavior and multi-scale habitat associations of Shoal Bass with riverine shoals. We assessed movement patterns and habitat use of Shoal Bass using radio telemetry in the lower 24 km of Ichawaynochaway Creek, a 6th -order tributary of the Flint River (Georgia). We observed increased movement in the spring, potentially reflecting behavior associated with spawning habitat selection. Shoal Bass occurred more frequently in close proximity to large shoals, and in areas with greater depth variability associated with edge and boundary conditions of shoal complexes. Despite previous studies that have documented high movement of this species in other systems, we found that the Ichawaynochaway Creek Shoal Bass population may be relatively sedentary and associated with specific shoal areas that provide suitable habitat. Affinity for specific mesohabitats within or near shoal complexes can be used to inform instream flow management and stocking program decisions, which may differentially influence this population that exhibits limited movement. 

​Ingram T., S. Sammons, A. Kaeser, R. Katz, S Sterrett. 2018. Spatial Ecology of Shoal Bass Micropterus cataractae in Ichawaynochaway Creek, Georgia. In Book Chapter: Managing Centrarchid Fisheries. American Fisheries Society. [link TBD]

Engaging stakeholders in natural resource decision-making

Natural resource managers frequently face difficult decisions, many of which involve diverse stakeholders, competing objectives, multiple management options, and uncertainty of outcomes. Participatory decision-making has emerged as an effective approach for addressing such decisions. This approach hinges on fostering a shared understanding of the issue, stakeholder buy-in, and co-creation of solutions as an effective means to address the issue. Effective engagement of stakeholders requires that facilitators have ample knowledge of relationships between stakeholders and the natural resource issue, strategic communication and trust within the community. This report explores issues and proposes

solutions involved in stakeholder engagement to provide a cursory resource for those interested in leading a participatory decision-making process. After introducing the topic of participatory decision-making and highlighting its benefits, steps for initiating the stakeholder engagement process, discussion of common challenges encountered and best practices for overcoming them are presented. In order to more efficiently address natural resource issues, those interested in leading participatory decision-making efforts should apply and pursue further training in the topics discussed in this report.


Support: U.S. Army Corps of Engineers Ecosystem Management and Restoration Research Program and Odum School of Ecology University of Georgia


Crawford B.A., R.A. Katz, and S.K. McKay. 2016. Engaging stakeholders in natural resource decision-making. EMRRP Technical Notes Collection. ERDC TN-EMRRP-XX. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.[link]

Dan Hocking

Evaluating landscape scale headwater stream management under climate change uncertainty


There is growing evidence that headwater stream ecosystems are especially vulnerable to changing climate and land use, but their conservation is challenged by the need to address threats at a landscape scale through coordination of multiple management agencies and landowners. Additionally, ecological processes that sustain species of special concern, such as eastern brook trout and stream salamanders, at regional scales are often fragemented among multiple stakeholders within watersheds. This project seeks to provide an example of collaborative landscape decision-making to address the conservation of headwater stream ecosystems in the face of climate change. We are using spatial multi-criteria decision analytic (MCDA) approaches and structured decision-making (SDM) to identify challenges to collaborative management at local and watershed scales. Decision makers often have multiple competing obejctives for headwater streams, which can have specific spatial and temporal demensions. We are identifying challenges for engaging decision-makers, evaluating landscape management outcomes, and implementing actions that can help inform watershed-scale management of headwater stream biota using several case-studies in three northeastern US watersheds involving federal, state, local governmental and non-govermental institutions. 


Funding: Northeast Climate Science Center and US Geological Survey Patuxent Wildlife Research Center.


M. Staudinger, L. Hilberg, M. Janowiak, C. Caldwell, A. D’Amato, E. Grant, R. Horton, R. Katz, C.

Neiil, K. Nislow, K. Potter, E. Rowland, C. Swanston, F. Thompson, K. Winiarski. 2015. Scale-Appropriate Adaptation Strategies and Actions in the Northeast and Midwest United States. In (Ed. Staudinger, Morelli, and Bryan), Integrating Climate Change into Northeast and Midwest State Wildlife Action Plans (pp.154-195). DOI Northeast Climate Science Center Report, Amherst, Massachusetts. [link]


Katz R.A., E. Grant, M. Runge, B. Connery, M. Crockett, E. Herland, S. Johnson, D. Kirk, J. Wofford, R. Bennett, K. Nislow, M. Norris, D. Hocking, B. Letcher, and A. Roy. 2014. Making decisions in complex landscapes: Headwater stream management across multiple federal agencies. U.S. Geological Survey and Fish and Wildlife, National Conservation Training Center, Structured Decision Making Workshop Report. [link]

Katz R.A., E. Grant, A. Roy, M. Runge, D. Hocking, B. Letcher. In prep. Challenges facing Collaborative Landscape Conservation: A Decision Analytic Perspective. To be submitted to Frontiers in Ecology and the Environment.

Katz R.A., E. Grant, D. Hocking, W. Fields, A. Brand, et al. In prep. Predicting stream salamander occurrence when data is lacking using expert opinion. To be submitted to Diversity and Distributions.

Estimating population dynamics of a native fluvial-dependent fish in relation to streamflow over multiple years using capture-mark-recapture


Extreme low streamflows are natural disturbances to aquatic populations. Although species in naturally intermittent streams display adaptations that enhance persistence during extreme events, the fate of populations in perennial streams during periods of unprecedented flow reductions are not well-understood. Biota that require flowing water habitats, i.e. “fluvial-dependent” species, may be especially susceptible to loss of flow from perennial systems. We estimated the abundance and local survival of a native fluvial-dependent fish species (Etheostoma inscriptum) across 5 years (2008-2012) encompassing historic low flows in a sixth-order southeastern USA perennial river (Middle Oconee River, Athens, GA). Based on capture-mark-recapture data, the study shoal may have acted as a refuge during severe drought, with increased young-of-the-year (YOY) recruitment and occasionally high immigration of adults. Contrary to expectations, summer and autumn survival rates (30 d) were not strongly depressed during low flow periods, despite 25–80% reductions in monthly discharge compared to long-term averages. Instead, YOY survival increased with lower minimum discharge as well as in response to rain events that increased high flow magnitude and low-flow variability. Age 1+ fish showed the opposite pattern, with apparent survival decreasing in response to increasing low-flow variability. Overall, results of this 5-year study of population dynamics for a small, nongame fish in a perennial river suggest that fluvial-dependent species can be resistant to extreme flow reductions through enhanced recruitment and high survival.


Funding: US Geological Survey, UGA Odum School of Ecology, UGA River Basin Center


R.A. Katz and M.C. Freeman. 2015. Evidence of population resistance to extreme low flows in a fluvial-dependent fish species. Canadian Journal of Fisheries and Aquatic Sciences 72(11): 1776-1787. [link]

Abundance dynamics vary with streamflow, habitat and network characteristics for multiple stream fish species in a piedmont watershed


Linking streamflow characteristics with changes in biotic populations is complicated by imperfect detection of individuals and uncertainty in the mediating effects of local habitat, reach geomorphology or network characteristics. Using a hierarchical modeling approach, we examined the relations between seasonal changes in fish abundances and low and high flow events using fish data collected at 12 stream reaches across 4 years (2010–2013) in a Piedmont watershed located in the Upper Flint River basin, GA. We used capture-mark-recapture methods at a subset of sites to estimate capture probabilities used to estimate abundances from counts of individuals in habitat units sampled on multiple dates. Using simulated daily flows (from a calibrated precipitation-runoff model) for each stream segment and an information theoretic approach, we evaluated the relative support for seasonal 10-d maximum and minimum flows, and of local habitat, channel confinement, stream size, and downstream link magnitude, as predictors of temporal changes in abundance five commonly occurring species. Results generally indicated that changes in abundances between sampling periods were positively related to short-term high and low flow events. However, these effects were species-specific and varied with catchment area for two cyprinid species, and with network position for two centrarchids species. High flow events potentially increased dispersal of stream fishes from larger tributaries into smaller tributaries. Additionally, extremely low flow events may have concentrated cyprinids and promoted young-of-year recruitment in reaches draining smaller catchments. These results provide insights into stream characteristics that may influence the effects of flow events on abundance dynamics of several native stream fishes in Piedmont streams.


Funding: US Geological Survey and UGA Odum School of Ecology 

Using population genetics to assess dispersal barriers in a small-stream cyprinid


Understanding the population structure and dispersal patterns of aquatic species is essential for predicting how species persist over ecological and evolutionary time-scales. However many population genetic studies of Cyprinidae, the largest family of freshwater fishes with many species imperiled, typically focus on broad scale patterns in diversity and divergence, which may not be relevant for local management. In this study, we investigated factors influencing stream fish population connectivity and dispersal of the Yellowfin shiner (Cyprinidae: Notropis lutipinnis), at a fine-spatial scale across a single watershed. Genetic diversity and genetic differentiation were relatively high among sites (HE range = 0.638 to 0.838 and FST mean = 0.044 and max = 0.167), given the maximum geographic distance between sites of 65km. Populationsabove high-gradient bedrock outcrops and dams were most divergent from all other populations. Genetic differentiation was positively related to geographic distance and negatively related to the proximity to the mainstem based on parameter estimates in the best- supported Bayesian generalized linear mixed model. Dispersal estimates (BIMr) indicated that populations with local extinctions were more likely recolonized by geographically close populations, and that migration was asymmetrical downstream of an historic milldam. Results indicate that this small-stream cyprinid generally follows a stepping-stone model of dispersal within tributaries, but that the mainstem is not a barrier to dispersal as previously hypothesized. Given our finding of increased gene flow among populations near the mainstem compared to far or isolated from the mainstem, maintaining connectivity of tributaries to the mainstem may be essential to minimize the impacts of environmental and demographic processes on populations of small-stream species. 


Funding: US Geological Survey, UGA Odum School of Ecology, UGA Department of Genetics, GA Museum of Natural History

Sean Sterrett

Sean Sterrett

Freshwater turtle habitat use, abundance and nutrient dynamics


Instream habitat characteristics influence the distribution of turtle species in riverine environments. We used radiotelemetry and a new sonar habitat mapping method to quantify instream habitat use by female Barbour’s Map Turtles (Graptemys barbouri -a GA state threatened species) in Ichawaynochaway Creek, a tributary to the Flint River in southwest GA. We used logistic regression and a Bayesian information-theoretic approach to evaluate habitat use relative to habitat availability. During 2007 and 2008, turtles used an average of 839±199 m of creek length and exhibited high site fidelity (mean 50% kernel density=0.23±0.05 ha). Substrate was more predictive of habitat use of female G. barbouri compared to large woody debris and water depth. Turtles generally used deeper habitats close to rocky-boulder and rocky-fine substrate with greater amounts of large woody debris. Estimates of home range size and habitat use found in this study improve our understanding of the spatial ecology of G. barbouri and provide a baseline for their habitat use in a relatively undisturbed section of stream. It is imperative to understand the spatial ecology of species, such as map turtles, that are particularly vulnerable to indirect effects of habitat modifications caused by impoundments, sedimentation, pollution, and snagging. 


Sterrett, S.C., L.L. Smith, A. Kaeser, R.A. Katz, J.C. Brock and J.C. Maerz. 2015. Spatial ecology of female Barbour’s map turtle (Graptemys barbouri) in Ichawaynochaway Creek. Copeia 103(2): 263-271. View.


Vertebrate skeletons have high phosphorus (P) content relative to other tissues. Variation in skeletal investment within and among species is hypothesised to predict variation in P demand, standing stock and recycling. These relationships have been examined among fish, but not in vertebrates with more robust skeletons, such as turtles. In this study, we (i) described freshwater turtle stoichiometry relative to skeletal mass, (ii) compared turtle body and excreta stoichiometry to patterns among fish and (iii) related turtle skeletal stoichiometry to turtle nutrient storage and recycling.  Skeleton constituted 82% of turtle dry mass. Phosphorus storage within turtle assemblages was high (0.2–0.45 kg/ha). Turtles excreted lower concentrations of P than fish. Our results demonstrate that P stored in the bone of turtles can represent a large standing stock of P in freshwaters. Our work suggests skeletal investment alone is not sufficient to predict an animal’s P demand and, by extension, their effects on nutrient recycling and that P demand may be determined by both skeletal investment and growth rate. Consequently, taxa with high body P, extreme longevity and slow growth rates, such as adult turtles, may serve as stable standing stocks of nutrients while also contributing proportionately to nutrient remineralisation.


Sterrett, S.C., R.A. Katz and J.C. Maerz. 2015. What can turtles teach us about ecological stoichiometry? Special Issue on “Synthesizing ecosystem-level effects of consumer-driven nutrient dynamics in freshwaters”. Freshwater Biology 60: 443–455. View.              Featured in first issue of "RatiosMatter" newsletter.

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