Northwest Fisheries Science Center (NWFSC) Fish Ecology FE - Migrational Behavior; FE - Watershed


Elwha River dam removal
Elwha River Dam Removal Study
This project focuses on ecosystem response to dam removals on the Elwha River, Washington State. The Elwha Dam removal is the largest project of its kind in the world, and the largest restorative action that has taken place in any Western U.S. Evolutionarily Significant Unit. Ecosystem response includes changes to physical habitat, aquatic food webs, thermal regime and all viable salmon parameters of listed and non-listed salmonids. The project is based on the development and implementation of the Elwha Monitoring and Adaptive Management Guidelines, a collaborative effort between the Fish Ecology Division at the NWFSC, the Lower Elwha Klallam Tribe, the U.S. Department of Fish and Wildlife Service, the U.S. Geological Survey, the WA Department of Fish and Wildlife, and the National Park Service. We employ a variety of metrics to efficiently monitor ecosystem condition over space and time. This project provides data to assess changes for listed Elwha River salmon and trout populations (Chinook salmon (Oncorhynchus tshawytscha), steelhead (O. mykiss), and bull trout (Salvelinus confluentus)), and evaluate cost effectiveness of salmon habitat recovery plans and actions. Such analyses are crucial to help inform future large-scale dam removals for multiple ESUs across the Western U.S. Additionally, this project is contributing to the development of steelhead capacity models across the Olympic Peninsula and to understanding salmonid reintroduction more generally (e.g Cedar River).

Research Themes

Ecosystem approach to improve management of marine resources
The California Current Large Marine Ecosystem, Puget Sound and the Columbia River Basin are home to a wide range of freshwater and marine resources that provide a wealth of ecosystem goods and services. Ensuring the resiliency and productivity of the California Current and Pacific Northwest ecosystems requires an integrated understanding of their structure, function, and vulnerability to increased human population growth in coastal communities and competing uses of coastal waterways and oceans. The NWFSC‘s approach to understanding these large ecosystems integrates studies across ecosystems (terrestrial, freshwater, and marine) and scientific disciplines to inform resource managers responsible for conserving marine resources.
Habitats to support sustainable fisheries and recovered populations
Healthy oceans, coastal waters, and riverine habitats provide the foundation for aquatic resources used by a diversity of species and society. Protecting marine, estuarine and freshwater ecosystems that support these species relies on science to link habitat condition/processes and the biological effects of restoration actions. The NWFSC provides the habitat science behind many management actions taken by NOAA Fisheries and other natural resource agencies to protect and recover aquatic ecosystems and living marine resources. The NWFSC also maintains a longstanding focus on toxic chemical contaminants, as a foundation for regional and national research on pollution threats to fisheries and protected resources.
Recovery and rebuilding of marine and coastal species
The Pacific Northwest is home to several iconic endangered species, including Pacific salmon and killer whales, and several rockfish species. Mandates such as the Endangered Species Act, MagnusonStevens Act, and the Marine Mammal Protection Act, grant NOAA Fisheries the authority to manage the recovery of depleted species and stocks. The NWFSC contributes to species recovery through research, monitoring and analysis, providing NOAA managers and regional stakeholders the tools and information they need to craft effective regulations and develop sustainable plans for recovery.
Sustainable, safe and secure seafood for healthy populations and vibrant communities
Effective fisheries management provides economic opportunities and ensures the long-term sustainability of fisheries and the habitats on which they depend. The NWFSC seeks to improve the quality and quantity of data used in stock assessments, the methods for assessing stocks and ecosystem sustainability within the context of human modification of the environment. The NWFSC also provides state-of-the-art science and technology to support aquaculture while protecting and maintaining ecosystem health. Further, pathogens, toxins from harmful algal blooms (HABs), chemical contaminants and other stressors of marine ecosystems pose significant risks to health of both seafood resources and to humans. The NWFSC focuses on research to improve understanding of those risks, how to forecast them, and identify means to mitigate their impacts.

Research Foci

Characterize ecological interactions (e.g. predation, competition, parasitism, disease, etc.) within and among species
Predator-prey interactions, inter- and intra-specific competition, and parasites and pathogens influence the survival, growth, and reproductive success of anadromous and marine fishes, marine mammals and other marine organisms. Moreover, anthropogenic stressors, such as pollution and fishing, can influence these interactions. Because of the complex nature of these interactions, addressing questions about ecological interactions will require novel field and laboratory studies and analyses. This includes ecosystem models, use of innovative technologies (e.g., otolith microchemistry and stable isotopes), integration of sample collection efforts with those of the Ocean Observing System entities on the west coast, and quantifying interactions among environmental stressors, species behavior and ecosystem processes.
Characterize the population biology of species, and develop and improve methods for predicting the status of populations
To evaluate species status and recovery, it is necessary to understand key aspects of the population biology of the species in question. This includes basic information on abundance, age structure, recruitment, spatial distribution, life history and how the species interacts with its ecosystem. For some recovering species, including most overfished groundfish stocks, many ESA-listed Pacific salmon stocks, and high profile species such as Southern Resident killer whales, this basic information is often reasonably well understood. For other recovering species, such as Pacific eulachon and some ESA-listed rockfish species, even basic information (e.g. stock abundance) is unknown. Even for well-studied species, key information on survival rates for critical life stages and how the environment affects these vital rates is lacking. Without basic information on species dynamics, achieving other goals such as quantifying relationships between human activities and species recovery or even knowing if species recovery goals are being met will not be successful. The NWFSC, in partnership with regional stakeholders, including states, tribes and industry, is conducting research to collect and monitor critical demographic information for recovering species.
Describe the relationships between human activities and species recovery, rebuilding and sustainability
Human activities play a major role in determining the status of species and stocks. Rebuilding and recovery therefore need to address how these activities affect their status. At the NWFSC, biophysical modeling is used to link specific human activities such as land use and pollution to habitat conditions, and then to link these conditions and other activities to particular life stages. These models can be used to quantitatively assess how human activities influence species abundance, productivity, distribution and diversity. Not surprisingly, altering human activities in some way is often necessary for species or stock recovery and rebuilding. It is therefore important to understand the socio-economic effects of alternative management structures. Gathering data on their economic costs and social impacts helps identify actions that are cost-effective. These actions will need to be resilient to potential changes in climate throughout the region. Research on how humans react to management strategies helps policy makers avoid those that lead to unintended consequences that can hinder rather than help recovery.
Develop effective and efficient habitat restoration and conservation techniques
Maintaining and re-establishing viability and sustainability of living marine resources requires conservation and rehabilitation or restoration of habitats upon which species depend. Common habitat restoration approaches and tech-niques often presume that habitats are static features of the environment, and that creation of stable habitats is a desirable restoration strategy. However, riverine, nearshore, and marine habitats are created and sustained by dynamic landscape, climatic, and oceanographic processes and biota are adapted to changing habitats that are within the range of natural variability. Hence, current restoration strategies often have limited success, in part because they fail to recognize larger scale processes that drive habitat change, and in part because they fail to recognize intrinsic habitat potential of individual restoration sites. The main goals of this research focus are to: improve understanding of how large-scale processes create diverse and dynamic habitats that support marine and anadromous species, better understand how human activities alter habitat-forming processes and habitats, develop new restoration techniques that are compatible with sustainable habitat-forming processes, and understand the variety of actions needed to adequately conserve intact critical habitats. In addition, NWFSC’s research will improve understanding of how new and existing habitat restoration and protection techniques affect fish and habitat at multiple scales (i.e., reach, watershed, Evolutionarily Significant Unit).
Develop methods to use physiological, biological and behavioral information to predict population-level processes
Understanding the biological processes occurring within organisms is a powerful way of understanding how environmental changes affect those organisms. Genetics, developmental, physiological and behavioral studies all provide important information for effective species recovery and rebuilding. Integrating this information into models is vital to predict how populations will respond to natural or human perturbations, and to assess the constraints to stock rebuilding efforts. For example, data on thermal tolerance and physiological responses to temperature can be used to explore changes caused by shifts in climate on reproductive behavior and productivity, viability, movement, habitat selection, and population dynamics. Similarly, data on contaminants that impact physiological processes (immune system, growth, development, reproduction, and general health) are critical in determining how these compounds affect population dynamics. Data on biological responses of organisms to ocean acidification are useful for understanding how acidification may affect individual development and survival. The NWFSC collects such information for several species that are of concern, targets of fisheries or otherwise important for overall ecosystem function. NWFSC scientists will continue to expand current efforts and develop methods to incorporate physiological, biological and behavioral data into population models in order to predict population-level processes from these individual level data.
Provide scientific support for the implementation of ecosystem-based management
Fisheries scientists and managers recognize the potential for ecosystem-based management to improve sustain the delivery of ecosystem goods and services, including sustainable fisheries resources. An Integrated Ecosystem Assessment (IEA) is one approach that examines all available information on relevant physical, chemical, ecological and human processes in relation to specified ecosystem management objectives. IEAs provide an efficient, transparent means of summarizing the status of ecosystem components, screening and prioritizing potential risks, and evaluating alternative management strategies against a backdrop of environmental variability. To perform IEAs of major ecosystems will require development of project components, including new and existing data, to develop a suite of indicators that characterize the ecosystem. Careful assessment of ecosystem indicators will provide a powerful means for assessing management efficacy and a basis for adapting and improving management practices. A major focus will be to produce the initial IEA of the California Current LME and then provide annual updates.
Support collaborative community-based data collection, dissemination, and analysis for fishers, fisheries management, science, marketing, seafood safety, and education
Data are no longer the sole province of the agency. As technologies advance, fishers are collecting and analyzing fleet data in near real time. Data collected by fishers are used by the fishing community to reduce bycatch, allocate fishery impacts, and trace products through the processing and marketing system. Fisher-collected data, in combination with survey and oceanographic data, satellite remote sensing, economic data, and sociocultural data provide improved understanding of fish stocks, fishing, and the near-shore ecosystem. Collaborative efforts increase the quantity and quality of data available to the agency for scientific analysis, modeling, fishery management, and conservation. Through cooperation with the science and management agencies, the fishing community stands to gain more control and flexibility of their fishing operations, including the potential for improved economic efficiency. Increased availability of fisheries data creates opportunities for education and outreach both in the school system and to the general public. Further, well-informed local leaders conversant in the latest fishery issues will help garner local support and fisher buy-in for improved information sharing. The NWFSC will work with industry groups to improve distributed data collection, compilation, and distribution for multiple uses in fisheries, management, science, marketing, and education.
Understand how climate influences ecosystem variability
Effective ecosystem management will require an understanding of how climate variability and climate change will alter riverine, estuarine, and marine habitats and consequently how this will affect ecosystem status, function and recovery. Key research elements include better understanding of historical ecological variability through traditional (i.e., indigenous) sources, exploring the vulnerability of key species and biotic communities to expected habitat changes, including decreasing stream flow, increased flood frequency, increasing stream temperature, sea level rise, ocean acidification, shifts in ocean currents, and changed frequency and extent of deoxygenated zones. A secondary goal is to improve understanding of how ecosystems respond to year-to-year and decadal climate variability. Achieving these research goals will provide NOAA and state and local governments with the knowledge and tools needed to incorporate climate change and variability into management of living marine resources.


Pacific herring
Pacific lamprey
Restoration trajectory
Time series of change in monitored metric; development towards management goal
adaptive management
Adaptive management of strategies and actions intended to recovery salmon populations
bioenergetics modeling
model of organism's energy budget
dam removal
related to removal of dams from rivers
effectiveness monitoring
evaluating whether actions had desired effects on physical, chemical, or biological processes
essential fish habitat
aquatic habitat where fish spawn, breed, feed, or grow to maturity.
Thaleichthys pacificus
flat depositional feature of a river valley adjoining the channel
food web
complex of interrelated food chains in an ecological community
forage fishes
small, energy-rich fishes that serve a key ecosystem role as prey for larger fish, marine mammals, and seabirds
use of genetic markers to determine differential reproductive success between adults with different life histories
quantifying effects of spawning salmon on resident food web using stable isotopes of C and N
juvenile salmonid
early life stages of salmonids
salmon food webs
habitats from the intertidal zone to the continental shelf
process-based restoration
habitat restoration of ecological processes (compare with form-based restoration)
recolonization dynamics of salmon following reintroduction
habitat restoration
restoration genetics
genetic analysis to understand success or failure of restoration process
all salmonids
water temperature
temperature of water


Benthic invertebrate response to Elwha dam removal
Morley, S.A., J.J. Duda, H.J. Coe, M. Elofson, E. Sampson, M. McHenry, M. Liermann, and G.R. Pess. In Prep. Benthic invertebrate response before, during, and after dam removal. To be submitted to Large-Scale Dam Removal and Ecosystem Restoration special issue of Frontiers in Ecology and Evolution.
Cedar River fish reintroduction
Kiffney, P. M., P. J. Lisi, M. Liermann, S. M. Naman, J. H. Anderson, M. H. Bond, G. R. Pess, M. E. Koehler, E. R. Buhle, T. W. Buerhens, R. S. Klett, J. R. Cram, and T. P. Quinn. 2023. Colonization of a temperate river by mobile fish following habitat reconnection. Ecosphere DOI: 10.1002/ecs.44336
Creation of public outreach position with Lower Elwha Klallam Tribe
Internship position created with Lower Elwha Klallam Tribe to focus on community engagement
Elwha 2022 Chinook salmon escapement
Denton, K., M. McHenry, E. Ward, M. Liermann, O. Stefankiv, W. Wells, and G. Pess 2023. 2022 Elwha River Chinook salmon escapement estimate based on DIDSON/ARIS Multi-beam SONAR data. Technical report to the Lower Elwha Tribe and Olympic National Park.
Elwha 2022 Coho salmon escapement
Denton, K. and O. Stefankiv. 2023. Estimating coho salmon escapement and mark rates in the Elwha River in 2022 using multi-beam SONAR technology. Technical report submitted to the Lower Elwha Tribe. 14.
Elwha 2022 Steelhead escapement
Denton, K., M. McHenry, E. Ward, M. Liermann, O. Stefankiv, W. Wells, and G. Pess 2023. 2022 Elwha River steelhead escapement estimate based on DIDSON/ARIS Multi-beam SONAR data. Technical report to the Lower Elwha Tribe and Olympic National Park.
Elwha 2022 smolt enumeration
McHenry, M. Elofson, M. Liermann, T. Bennett, S. Corbett, and G. Pess. 2023. 2022 Elwha River smolt enumeration project report. Summary Report. Technical report to Olympic National Park. McHenry, M., J. McMillan, R. Moses, and G. Pess. 2023. Coho salmon relocations and redd
Elwha Chinook salmon out migration timing
Liermann, M., Fullerton, A., Morley, S., Hinkeley, L., McHenry, M. Bennet, T., Elofson, M. and Pess G.R. Predicted changes in Chinook Salmon out-migration timing and size in response spawning distribution expansion and climate change To be submitted to Large-Scale Dam Removal and Ecosystem Restoration special issue of Frontiers in Ecology and Evolution.
Elwha Coho redd surveys
McHenry, M., J. McMillan, R. Moses, and G. Pess. 2023. Coho salmon relocations and redd surveys in the Elwha River 2011-2019: Summary report. Technical report to Olympic National Park.
Elwha Community and Citizen Science
Eitzel, M.V., Morley, S., Behymer, C., Meyer, R., Kagley, A., Ballard, H., Jadallah, C., Duda, J., Jennings, L., Miller, I., Stapleton, J., Shaffer, A., Miller, A., Shafroth, P., and Blackie, B. (2023) Community and Citizen Science on the Elwha River: Past, Present, and Future. UC Davis Center for Community and Citizen Science and Elwha ScienceScape.
Elwha Data Inventory Portal
Web-based data portal to easily access all NWFSC Elwha datasets
Elwha community and citizen science
Eitzel, M.V., Morley, S., Behymer, C., Meyer, R., Kagley, A., Ballard, H., Jadallah, C., Duda, J., Jennings, L., Miller, I., Stapleton, J., Shaffer, A., Miller, A., Shafroth, P., and Blackie, B. In Prep. Community and Citizen Science on the Elwha River: Past, Present, and Future. To be submitted to Large-Scale Dam Removal and Ecosystem Restoration special issue of Frontiers in Ecology and Evolution.
Elwha distribution of Chinook salmon spawning
McHenry, M., G. Pess, and J. Anderson. 2023. Spatial distribution of Chinook salmon spawning in the Elwha River, Washington State during dam removal and early stages of recolonization (2012-2020). Technical report to Olympic National Park.
Elwha proportion of hatchery-origin steelhead
Peters, R.J., K. Denton, and M.C. Liermann. 2023. Proportion of hatchery origin winter steelhead and broodstock collection in the Elwha River: 2022. Report to the Lower Elwha Klallam Tribe, fulfilling LEKT agreement # LEKT-FWS-2019-01. Project # 4937-1336, U.S. Fish and Wildlife Service Report, Washington Field Office, Lacey, WA.
Elwha winter steelhead surveys
Mchenry, M., R. Moses, J. McMillan, H. Connor, K. Sutton, and G. Pess. 2022. Summary of 2022 winter steelhead surveys in the Elwha River. Technical report to Olympic National Park.
Emergency of diverse life history in juvenile salmonids
Munsch, S.H., M. McHenry, M.C. Liermann, T.R. Bennett, J.R. Mcmillan, and G.R. Pess. In Prep.. Dam removal enables diverse juvenile life histories to emerge in threatened salmonids repopulating a heterogeneous landscape. To be submitted to Large-Scale Dam Removal and Ecosystem Restoration special issue of Frontiers in Ecology and Evolution.
Leaf litter decomposition response to Elwha dam removal
LeRoy, C., S.A. Morley, J.J. Duda, et al. In Prep. Leaf litter decomposition and detrital communities following the removal of two large dams on the Elwha River (WA, USA). To be submitted to Large-Scale Dam Removal and Ecosystem Restoration special issue of Frontiers in Ecology and Evolution.
Ongoing outreach and educational activities
Regular field trips and presentations to educational and community organizations to support ongoing participation in Elwha research - community and citizen science
Response of Chinook salmon and steelhead trout to Elwha dam removal
Pess, G.R., M. McHenry, K. Denton, J.H. Anderson, J.R. McMillan, M.C. Liermann, R. Peters, S. Brenkman, T.R. Bennett, J. Duda, and K. Hanson. In Prep. Initial response of Chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus mykiss) to removal of two dams on the Elwha River. To be submitted to Large-Scale Dam Removal and Ecosystem Restoration special issue of Frontiers in Ecology and Evolution.
Response of Chinook salmon and steelhead trout to Elwha dam removal
Pess, G.R. et al. In Review. Initial response of Chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus. m. irideus) to the removal of the Elwha River dams, Washington State, U.S.A. Canadian Journal of Fisheries and Aquatic Sciences.
Restoration of riverine connectivity
Kiffney, P. M., J. H. Anderson, E. Jones, F. Kretschmer, and G. R. Pess. in review. Natural colonization of a small forest stream by native anadromous coho salmon following restoration of riverine connectivity.
Veterans Conservation Corps Internship
VCC internship hosted by Migrational Behavior and Watershed Program


Class Actinopterygii
ray-finned fishes
Class Insecta
Family Salmonidae
Genus Oncorhynchus
Order Salmoniformes
Phylum Chordata
Species Ammodytes hexapterus
Pacific sand lance
Species Clupea pallasii
Pacific herring
Species Hypomesus pretiosus
surf smelt
Species Lampetra tridentata
Pacific lamprey
Species Oncorhynchus clarkii
cutthroat trout
Species Oncorhynchus gorbuscha
humpback salmon, pink salmon
Species Oncorhynchus keta
chum salmon, dog salmon, Keta salmon
Species Oncorhynchus kisutch
Coho salmon, silver salmon
Species Oncorhynchus mykiss
rainbow trout, steelhead trout, syeelhead trout
Species Oncorhynchus nerka
kokanee, red salmon, sockeye salmon
Species Oncorhynchus tshawytscha
Chinook salmon, king salmon, spring salmon
Species Spirinchus thaleichthys
longfin smelt
Species Thaleichthys pacificus


Aimee Fullerton
Internal Collaborator
Anna Kagley
George Pess
Principal Investigator
George Pess
Principal Investigator
Karrie Hanson
Kinsey Frick
Krista Nichols
Internal Collaborator
Martin Liermann
Martin Liermann
Peter Kiffney
Internal Collaborator
Sarah Morley
Todd Bennett
Todd Bennett