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  • Washington Sea Grant Shellfish Aquaculture in Washington State • 2015 | a

    Shellfish Aquaculture in Washington State

    Final Report to the Washington State Legislature

    December 2015

    Washington Sea Grant

  • Acknowledgments Washington Sea Grant expresses its appreciation to the many individuals who provided information and support for this report. In particular, we gratefully acknowledge funding pro- vided by the Washington State Legislature, National Oceanic and Atmospheric Administration, and the University of Washington. We also would like to thank the many academic, state, federal, tribal, industry and other experts on shellfish aquaculture who cooperated with investigators to make this research possible.

    Investigators/staff Jonathan C.P. Reum, Research Manager

    Neil S. Banas

    Wei Cheng

    Penelope Dalton

    Kevin Decker

    Marcus Duke

    Dara Farrell

    Recommended citation Washington Sea Grant (2015) Shellfish aquaculture in Washington State. Final report to the Washington State Legislature, 84 p.

    Shellfish Aquaculture in Washington State Final Report to the Washington State Legislature • December 2015

    This report is available online at

    This report provides the final results of Washington Sea Grant studies conducted from July 1, 2013 to

    November 30, 2015 on the effects of evolving shellfish aquaculture techniques and practices on Washington’s

    marine ecosystems and economy. Funding provided by a proviso in Section 606(1) of the adopted 2013 –

    2015 State Operating Budget.

    Bridget E. Ferriss

    Chris J. Harvey

    Teri King

    Kate Litle

    P. Sean McDonald

    Robyn Ricks

    Jennifer Runyan

    MaryAnn Wagner


    Washington Sea Grant 3716 Brooklyn Avenue N.E. Seattle, WA 98105-6716


    WSG-TR 15-03

  • Contents

  • Washington Sea Grant Overview i


    Shellfish aquaculture is both culturally significant and economically important to Washington communities, and in many locations interest exists in expanding production. To promote and manage shellfish aquaculture in a sustainable manner, it is essential to understand the potential ecological and economic effects, both positive and negative, of evolving aquaculture practices. At the direction of the Washington State legislature in 2013, Washington Sea Grant initiated a research program to assess and develop tools and resources that could help growers, managers, and other coastal residents address a range of issues. The research program included an economic analysis, three pilot modeling studies, and an overview of spa- tial data approaches:

    1. An economic trend analysis of Washington shellfish production and value (p. 1) details the economic contribution of shellfish aquaculture to different coastal areas in Washington and to the state. The analysis underscores the contribution of aquaculture to generating revenue in the state economy. Results from this work should help guide future development of economic studies and social science on the state aquaculture industry.

    2. An ecosystem model of Central Puget Sound (p. 15) was developed to explore the potential influence of aquaculture on the environment and, alternatively, how environmental changes affect aquaculture. In this region, sufficient data are available to build a quantitative ecosystem model, which can be used to explore different management scenarios. For example, a finding from the model that aquaculture gear had stronger ecosystem impacts than the farmed geoduck themselves points to development of innovative gear and new culture techniques as a promising approach for minimizing impacts.

    3. Relying on limited data, qualitative food web models of South Puget Sound and Willapa Bay (p. 35) can be used to identify whether shellfish populations or other food web members are likely to increase or decrease given a particular management or environmental scenario. The models for Willapa Bay, for instance, indicate that ocean acidification could potentially result in fewer Manila clams but more eelgrasses and phytoplankton. The models were relatively simple to build and can be easily refined using alternative scenarios.

    4. An oceanographic study advances development of a high-resolution circulation model for South Puget Sound (p. 59). In a preliminary analysis, the model suggests that aquaculture may have the capacity to control phytoplankton concentrations in localized areas. The results strongly encourage further investigation of both the possible downstream effects on other consumers of phytoplankton and a possible role for aquaculture in mitigating eutrophication (which can be associated with

    water quality issues) in western South Puget Sound. The model also has a wide range of other potential applications and could be an important first step towards better prediction of seawater oxygen and acidity levels in South Puget Sound.

    5. A framework and data assessment for spatial decision support in aquaculture (p. 71) can further the development of tools to support decisions such as where to site shellfish farms. A decision support study outlines the framework and includes an assessment of publicly available spatial data in Washington State that will likely be relevant. It provides a starting point for growers, managers, and researchers interested in developing spatial tools to weigh the potential ecological, social, and economic tradeoffs involved in farm placement.


    Commercial shellfish cultivation has taken place in Washing-ton waters since the mid-1800s and has evolved in terms of the species farmed, methods used, product markets, and acre- age under cultivation. Today Washington State is the nation’s leading producer of farmed clams, oysters, and mussels. The 2011 Washington Shellfish Initiative estimated that state shell- fish growers directly and indirectly employ more than 3,200 people and provide an estimated total economic contribution of $270 million. Production includes hatcheries, nurseries, farms, and processing, distributing, wholesale, and retail operations. In addition to their commercial importance, shellfish are cen- tral to tribal cultures and economies and contribute to recre- ational opportunities and tourism.

    Shellfish are an important component of marine ecosystems, and environmental changes and stressors can affect shellfish aquaculture production. For example, the Washington coast is especially vulnerable to ocean acidification (OA), a change in ocean chemistry that interferes with shell development in some marine organisms and which may potentially affect both cultured species and marine food web dynamics. Harmful algal blooms and aquatic invasive species also continue to pose seri- ous threats to shellfish resources and seafood product safety. Meanwhile, climate change has introduced additional variability in environmental parameters like water temperature, contrib- uting to and interacting with other changes.

    Shifts in Washington’s coastal environment have been coupled with growing human populations that affect coastal water quality and put additional pressure on regional shellfish resources. Approximately 65 percent of state residents live in coastal counties, and the Puget Sound region alone is expected to grow almost 35 percent, to five million people, by 2040. The

  • ii | Washington Sea Grant Shellfish Aquaculture in Washington State • 2015

    complex challenges facing shellfish managers and growers have spurred interest in more comprehensive, ecosystem-based research that integrates environmental, social, economic, and institutional information.


    Housed in the UW College of the Environment, Washington Sea Grant is a federal–university partnership that conducts research, education, and outreach to address Washington’s coastal and marine issues and needs. In 2013, the Washington State Legislature directed Washington Sea Grant to conduct a two-year scientific research program specifically addressing state concerns related to shellfish aquaculture. The legislative language specified that funding be used to:

    … commission scientific research studies that examine pos- sible negative and positive effects, including the cumulative effects and the economic contribution, of evolving shellfish aquaculture techniques and practices on Washington’s economy and marine ecosystems. The research conducted for the studies is not intended to be a basis for an increase in the number of shellfish harvesting permits available and should be coordinated with any research efforts related to ocean acidifi- cation.

    As a first step, Washington Sea Grant convened a series of scop- ing sessions with researchers and faculty from the University of Washington, Washington Ocean Acidification Center, and National Oceanic and Atmospheric Administration (NOAA). Based on the recommendations of session participants, a research team was assembled to develop a scope of work for the program. Although shellfish are cul