• Projects
  • Early Marine Survival of Puget Sound Steelhead


Northwest Fisheries Science Center (NWFSC) Environmental and Fisheries Sciences EFS - Fisheries Enhancement and Conservation


Salish Sea Marine Survival
Early Marine Survival of Puget Sound Steelhead
The primary objectives of this study are to estimate a predation rate by harbor seals on steelhead smolt in Puget Sound, and determine whether predation by harbor seals differs by region. Nisqually River steelhead will be acoustic tagged, and 12 - 18 seals will be fitted with GPS/acoustic receiver instrument packs. Tag detection capabilities will be expanded by i) monitoring harbor seals in South and Central Puget Sound and Admiralty Inlet, ii) placing stationary receivers at seal haulouts and at random locations not frequented by harbor seals, iii) conducting mobile tracking to locate tags remaining in Puget Sound after the smolt outmigration period. Seal time at depth and locations will be quantified in such a manner that estimates the amount of time seals spend at haulout locations to estimate the probability that a tag consumed by a harbor seal would be defecated near a haulout site. Data on harbor seal abundance, behavior, steelhead tag locations, and smolt abundance will be combined to estimate the predation rate and total number of smolts consumed by harbor seals.
In addition, recent fish health assays indicate high infection prevalence (87-100%) and intensity (800-2500 cysts/fish) of Nanophyetus salmonica in steelhead outmigrating from Central (Green) and South (Nisqually) Puget Sound Rivers. South and Central Puget Sound steelhead populations generally experience lower early marine survival rates than those from North Puget Sound rivers, where Nanophyetus infections in assayed steelhead were absent. High infection intensity among freshwater outmigrants could contribute to rapid mortality shortly after seawater entry. This study will use acoustic telemetry to evaluate differences in the early marine survival (near river mouth to Pacific Ocean) of specific pathogen-free (SPF) and Nanophyetus-infected Puget Sound steelhead smolts. This approach will help us understand effects of Nanophyetus infection at different stages of the steelhead smolt migration through Puget Sound.

Research Themes

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.

Research Foci

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.
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.


Harbor seal
Marine survival
Nanophyetus salmincola
Parasitic trematode
Predation on steelhead smolts migrating through Puget Sound
Salish Sea
includes Puget Sound, Strait of Juan de Fuca, in Washington state
Oncorhynchus mykiss


None associated


Species Oncorhynchus mykiss
rainbow trout, steelhead trout, syeelhead trout
Species Phoca vitulina
common seal, harbour seal


Barry Berejikian
Megan Moore
Megan Moore
Rob Endicott