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Northwest Fisheries Science Center (NWFSC) Conservation Biology CB - Ecosystem Science


Stable Isotopes in Predators
Characterizing ecosystem role of sharks
This work uses white muscle tissues collected from sixgill and sevengill sharks to characterize the diet of each species. Tissues from prey species have also been prepared in order to initialize the models. We used mixing models to determine the probabilities of each prey species being in the diet of these top predators. These data will be used to predict which prey groups are impacted by these species, and then used in conjunction with patterns of daily, seasonal, and annual movement patterns to examine the variation in predatory impact across space and time among the various prey groups.

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.

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.
Describe the interaction between human activities, particularly harvest of marine resources, and ecosystem function
Humans are an integral component of ecosystems. These ecosystems provide goods and services such as fish and seafood harvests, but these activities and others such as habitat alteration, pollution, and ocean acidification, can have strong impacts. Understanding the nature of these interactions will require observational and experimental studies aimed at identifying ecosystem-level responses to human activities, both individually and cumulatively, as well as human responses to ecosystem changes. Modeling spatial choices for harvesting and other human activities that are affected by ecosystem integrity, for example, can support a better understanding of the effects of ecosystembased management actions.


stable isotopes
isotopes of an element that have the same atomic number, but different atomic mass


None associated


Species Hexanchus griseus
bluntnose sixgill shark, six-gill shark, six-gilled shark, sixgill shark
Species Notorynchus cepedianus
broadnose sevengill shark, sevengill shark


Chris Harvey
Gregory Williams
Kelly Andrews
Nick Tolimieri
Phil Levin