Summary of the 2008 

NOAA National Symposium on 

Shellfish & the Environment 

Prepared by the 

NOAA Aquaculture Program 

in cooperation with the 

NOAA Office of Habitat Conservation

September 2009 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 2

Summary of the 2008 

NOAA National Symposium on 

Shellfish & the Environment 

You may download an electronic version of this report from: 

http://aquaculture.noaa.gov

You may download presentations from the meeting at: 

http://aquaculture.noaa.gov/news/shellfishsymposium.html

This document should be cited as follows: 

Summary of the 2008 NOAA National Symposium on Shellfish & the Environment, 

September 2009 

For more information: 

NOAA Aquaculture Program Office 

1315 East-West Hwy. 

SSMC-3 - Route: F/AQ 

Silver Spring MD 20910 

Phone: (301) 713-9079 

Website: http://Aquaculture.noaa.gov
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 3

Table of Contents 

Background _________________________________________________________ 4 

Top Three Themes from the Symposium __________________________________ 5 

Syntheses of the Breakout Discussions ____________________________________ 6 

· Eutrophication/Carrying Capacity/Water Quality

· Genetics/Invasives/ Disease 

· Habitat and Gear/Education 

· Societal Interactions/Engagement 

List of Presentations _________________________________________________ 10 

Summaries of the Individual Presentations ________________________________11 

· Dr. Jon Grant, Dalhousie University 

· Dr. Peter Cranford, Fisheries and Oceans Canada 

· Dr. JoAnn Burkholder, North Carolina State University 

· Dr. Odd Lindhal, Sweden’s Kristineberg Marine Biological Station 

· Dr. Dianna Padilla, State University of New York - Stony Brook 

· Dr. Dennis Hedgecock, University of Southern California 

· Dr. Roxanna Smolowitz, New England Aquarium 

· Dr. Loren Coen, Sanibel-Captiva Conservation Foundation 

· Dr. Brad Harris, University of Massachusetts - Dartmouth 

· Dr. Gary Jensen, USDA-CSREES 

· Colin Brannen, World Wildlife Fund-US 

· Dr. George Leonard, Ocean Conservancy 

· Dr. John Hargreaves, Baton Rouge, Louisiana 

· Dr. Gary Wikfors, NOAA Northeast Fisheries Science Center-Milford Laboratory 

· Dr. Susan Stonich, University of California - Santa Barbara 

Appendix 1 – Agenda ________________________________________________ 25 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 4

Background 

On June 9–10, 2008, the National Oceanic and Atmospheric Administration’s Aquaculture 

and Habitat Conservation programs hosted the 2008 National Symposium on Shellfish and 

the Environment in Warwick, Rhode Island. Organized by Dr. Sandy Shumway of the 

University of Connecticut, the symposium was designed to address important issues 

regarding shellfish aquaculture in the United States. Three key themes were discussed: 

• Educating the public on the benefits of shellfish aquaculture; 

• Bringing clarity and consistency to regulations for this industry, and 

• Refinement of best management practices essential for the growth and success of the 

shellfish industry. 

Topics included carrying capacity, eutrophication, water quality, habitat, invasive species, 

genetics, aquatic animal health, social aspects, gear/harvest impacts, and cumulative impacts. 

U.S. Senator Jack Reed of Rhode Island was a featured speaker on the first day of the 

symposium. In his remarks Senator Reed highlighted the proactive approach the Ocean State 

is taking to ensure a sustainable aquaculture industry and protect the marine environment. 

Other speakers included scientific and policy experts from the United States, Canada, and 

Europe who addressed a range of topics focused on policy, regulation, and the environmental 

effects of shellfish culture. Participants included growers and representatives from the U.S. 

shellfish industry, non-government organizations, researchers, and federal and state officials. 

NOAA’s representatives included Tim Keeney, Deputy Undersecretary for Oceans & 

Atmosphere; Brian Pawlak, Deputy Director of the NOAA Office of Habitat Conservation; 

and Dr. Michael Rubino, Manager of the NOAA Aquaculture Program. 

This summary includes a synthesis of the top three themes that emerged from the discussions 

held at the symposium, followed by highlights of the presentations given by each of the 

invited speakers. The information generated by the symposium will be used to facilitate 

public policy and resource management discussions and decisions for shellfish aquaculture in 

the United States, and to inform research priorities. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 5

Top Three Themes from the Symposium 

 The following points emerged as the top three themes from the breakout sessions held at the 

NOAA National Shellfish Symposium. 

• The need for improved understanding of the interactions, both positive and negative, 

of shellfish aquaculture and the environment. Better information and analysis will 

allow for refinement of Best Management Practices (BMPs) that are essential to a 

sustainable aquaculture industry. Participants emphasized that BMPs should be 

standardized, recognizing that practices, environments, and species vary regionally. 

• More vigorous education and outreach efforts are critical to the future of U.S. 

aquaculture, including the need to increase public knowledge and understanding of 

the beneficial effects of sustainable shellfish farming. Throughout the symposium, the 

value of and need for increased education and outreach to the public was raised as the 

most important next step. Participants emphasized that Sea Grant agents, industry 

members, environmental NGOs, and other stakeholders need to engage in more 

extensive local education and outreach (e.g., school programs/visits, oyster gardening, 

and food festivals) to improve public understanding of shellfish aquaculture. 

Potential solutions included targeting public education campaigns to riparian 

landowners and educating the public specifically on the environmental and economic 

benefits of shellfish aquaculture. 

• Shellfish aquaculture policies and regulations on all levels are often fragmented and 

confusing limiting restoration aquaculture and commercial shellfish farming. 

Proposed solutions included coordinated coastal land use planning to keep shellfish 

beds, restore beds, to protect natural environmental features, and make room to 

establish areas dedicated for shellfish aquaculture. Policies and regulations should 

take into account local knowledge and experience, as well as the need for consistency 

and predictability. Proposed solutions included coordinated coastal land use planning 

to keep shellfish beds, restore beds, to protect natural environmental features, and 

establish areas dedicated for shellfish aquaculture.
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 6

Syntheses of the Breakout Discussions 

Participants at the symposium were randomly assigned to participate in breakout groups to 

discuss issues of particular importance and relevance to shellfish aquaculture in the United 

States. Each participant had the opportunity to participate in two of the four breakout 

discussions. 

The following text summarizes the major points recorded and highlighted in the four 

breakout sessions that focused on: 

1. Eutrophication/Carrying Capacity/Water Quality 

2. Genetics/Invasives/ Disease 

3. Habitat and Gear/Education 

4. Societal Interactions/Engagement 

1. Eutrophication/Carrying Capacity/Water Quality 

This session focused on the ecosystem interactions of shellfish aquaculture and the 

environment. Discussions highlighted the need for: 

• A common language and understanding as well as quantitative definitions regarding 

key metrics, values, and terminology for shellfish aquaculture. A standard starting 

point for comparisons. For example, should current operations be compared to 

present values, historic values, or something else? And, at what scale (temporal 

and/or spatial) must effects be analyzed? 

• Improved data collection practices and methods to provide species-specific data on 

benthic impacts, sedimentation, harvesting impacts, nutrient removal capabilities, and 

other factors. 

• Considering source data from industry as well as research. 

• Data and information on water quality that is easily accessible to researchers, 

regulators, and the public in useful formats, such as bibliographies or a web-based 

information 

• Implementation of a meta-analysis of existing data to help answer questions and 

identify information gaps related to water quality. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 7

2. Genetics/Invasives/Disease 

This session highlighted issues of genetic management and husbandry, non-native 

introductions, and the potential role of farmed shellfish as vectors for disease or parasites. A 

central question was: Should farmed species be domesticated (much like modern agriculture) 

to produce lineages that are very different than wild stocks, or should broodstock be managed 

to maintain genetic diversity as found in abundant wild stocks? Responses to this question 

included the view that although domestication would allow for “genetic improvement,” such 

as disease-resistant strains of shellfish, faster growth, higher meat yields, and other desirable 

traits, the chance of interbreeding wild and farmed stocks should be carefully considered to 

address the possibility of gene pool effects. 

Reflecting the discussions held in the water quality session, participants in this session 

emphasized that researchers and regulators need clear a definition of what constitutes an 

invasive species. Discussion here focused on the need to establish common reference points 

for the time and/or spatial scales that are considered; boundary lines for native species; 

intentional and accidental introductions; recognition of species and strains; and how 

regulators and others establish a baseline for what originally existed in an area. 

 

The importance of scientific expertise was highlighted as a key component for evaluating 

benefits, risks, and other issues. This discussion also included consideration of non-biological 

risks and public perception of the use of sterile and triploid stocks in shellfish aquaculture. 

The discussions in this session also addressed: 

• The need for better understanding of shellfish disease, either through increased 

federal funding of research and/or the establishment of disease testing centers with 

standardized testing protocols. 

• Additional research to develop more reliable methods for ensuring sterility of stock. 

• Using introduced species as a regional and species-specific decision. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 8

3. Habitat and Gear/Education 

The discussions concerning habitat and gear noted there are observed benefits to the 

environment from shellfish aquaculture and that current research showing the ecosystem 

benefits of shellfish aquaculture is well-recognized and accepted by industry. Several 

recommendations on future directions for research and regulation were discussed. Those 

included: 

• Further quantifying the benefits and interactions of shellfish aquaculture with the 

environment, including the positive effects of structure as refugia and habitat, the 

relationship between gear and increased biodiversity of native species, and the 

reduction of turbidity in the water column, which aids eelgrass and other vegetation. 

• An economic valuation of ecosystem services provided by shellfish aquaculture. 

Habitat disturbances inherent in shellfish harvest methods were also discussed. Suggestions 

for next steps included an assessment of the frequency and magnitude of disturbances, and 

recovery time from habitat disturbances such as trampling by humans, harvesting, dredging, 

structure removal, and others. Because the effects and impacts of harvest methods differ 

depending upon gear and harvest infrastructure, a comparative gear analysis of habitat 

disturbances was also discussed. 

As highlighted earlier, the need for more public education and outreach regarding the 

benefits of shellfish aquaculture was a common element in every discussion held at the 

symposium. In addition to the numerous calls for public education across breakout groups 

and topics, participants emphasized the need for better information flow to regulators to help 

streamline the permits process. Suggestions included providing regulators and permit writers 

with: 

• Additional training regarding shellfish aquaculture. 

• Better access to resources that provide the best, most recent science and research. 

• A Permit Writer’s Guidebook with region-specific supplements. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 9

4. Societal Interactions/Engagement 

 

As with the other breakout sessions, public education and outreach was most often identified 

as the best way to engage and interact with the interested public regarding shellfish 

aquaculture. Key messages in any education effort should include: 

• Shellfish require clean water and help to improve water quality through filtration. 

• Clean water improves the quality of life for people living along the coasts. 

Participants noted that large-scale direct marketing campaigns are a necessary step in the 

public education process. Such marketing could highlight the positive benefits of shellfish 

aquaculture and feature farms and farmers, not just products. The use of celebrity chefs was 

also suggested. 

Other suggestions for societal engagement included: 

• Connecting with Community Supported Agriculture (CSA) frameworks, or other 

networks that highlight local food sources to the community. 

• Pursuing eco-labeling and/or sustainable certifications to promote the sustainability of 

their product. 

• Conducting a public opinion survey to help broadly identify the thoughts and values 

surrounding shellfish aquaculture. 

• Training regulators in conflict resolution. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 10

List of Presentations 

o Shellfish Culture in the Realm of Ecosystem-based Management, Dr. Jon Grant, Dalhousie 

University 

o Chronic Effects of Eutrophication on Bivalve Shellfish, Dr. JoAnn M. Burkholder, North 

Carolina State University 

o Ecosystem Interactions with Intensive Mussel Aquaculture: Research Applications, Dr. 

Peter Cranford, Department of Fisheries and Oceans, Canada 

o Mussel Farming as a Tool for Remediation of Coastal Waters: Experiences from Sweden, 

Dr. Odd Lindahl, Kristineberg Marine Biological Station, Sweden 

o Marine Invaders and Aquaculture: Sources, Biodiversity, Impacts and Consequences, Dr. 

Dianna Padilla, Stony Brook University 

o Genetics of Shellfish, Wild and Farmed, Dr. Dennis Hedgecock, University of Southern 

California 

o Effects of Environment and Culture Techniques on Shellfish Disease Severity and 

Prevalence, Dr. Roxanna Smolowitz, New England Aquarium 

o Importance of Bivalve Molluscs: The Habitat They Generate and Associated Ecosystem 

Services, Dr. Loren Coen, Sanibel-Captiva Conservation Foundation 

o Assessing the Impacts of Shellfish Aquaculture Harvest: Lessons Learned, Dr. Bradley P. 

Harris (University of Massachusetts, Dartmouth), Dr. Kevin D. E. Stokesbury (University of 

Massachusetts, Dartmouth), and Dr. Edward P. Baker (University of Rhode Island) 

o Case Studies–Perspective: Education and Engagement, Dr. Gary Jensen and Dr. Jeff 

Silverstein, U.S. Department of Agriculture (USDA) 

o World Wildlife Fund Molluscan Shellfish Dialogues, Colin Brannen, World Wildlife FundU.S. 

o Shellfish Aquaculture and the Sustainable Seafood Movement, Dr. George H. Leonard, The 

Ocean Conservancy 

o Thoughts on the Environmental Concerns with Molluscan Shellfish Aquaculture 

Development, Dr. Gary H. Wikfors, NOAA Northeast Fishery Science Center – Milford Lab 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 11

Summaries of the Individual Presentations

Throughout the course of the symposium experts in the field of shellfish aquaculture and the 

environment provided presentations to facilitate and inform the discussions. Below are the 

abstracts of the presentations, and following each abstract is a brief synthesis of the 

presenter’s key points. 

Shellfish Culture in the Realm of Ecosystem-based Management 

Dr. Jon Grant, Dalhousie University 

Ecosystem-based management (EBM) is a developing concept, applied largely to conservation of 

harvest fisheries. For aquaculture, it can have a more detailed meaning in terms of management, since 

the location and biomass of culture species is controlled. Aquaculture may have a variety of 

interactions with the ecosystem, since high biomasses of herbivorous bivalves are emplaced within 

the trophic web. These include seston depletion (the uptake of plankton by the shellfish primarily for 

feed) via filtration and eutrophication (nutrient pollution) via biodeposition. There is a sustainable 

level of shellfish culture, estimable by ecosystem modeling, but in any management scenario, goals 

must be defined—an often deficient aspect of EBM. Management variables include levels of nutrients 

and oxygen, biodiversity, and habitat conservation. The options for mechanisms of controlling coastal 

ecosystems are limited, however; discharges of contaminants and nutrients can be regulated and, in 

the case of aquaculture, biomass is controlled to limit potential localized organic loading. There are 

various examples of models applied to these problems, but a reasonable progression is to start simple 

(box or index models) and proceed to more complex models (fully coupled physical-biological) if 

necessary. In any event, the science is sufficient to reliably yield a variety of predictions related to 

aquaculture management at the ecosystem level. 

Highlights from the Presentation: 

• Aquaculture can be a natural part of coastal ecosystems and can be made sustainable by 

understanding its interaction with the system. 

• The point above is an essential aspect of now-popular ecosystem-based management. 

• It is important to define goals for ecosystem management as they relate to water and sediment 

quality, coastal resource use, biodiversity, etc. 

• Dominant effects of bivalve culture include seston depletion and localized organic deposition. 

• Predictive tools are essential in managing this process, likely based in ecosystem modeling. 

• Models are of several types, including box models and fully coupled physical-biological 

simulations. 

• Models of marine systems must include a biogeochemical component as well as an explicit 

physical oceanographic model. 

• Simpler models are best for initial approaches, leading to more complex models if required. 

• Aquaculture may be fully integrated into EBM with reliable output from ecosystem-level models. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 12

Ecosystem Interactions with Intensive Mussel Aquaculture: Research Applications 

Dr. Peter Cranford, Department of Fisheries and Oceans, Canada 

Aquaculture is the only realistic means of resolving the growing disparity between seafood 

production and demand. Although shellfish aquaculture in Canada is highly diverse in 

structure, capital, and material infrastructure, the most rapid development has occurred with 

mussel culture. Ecosystem science is regarded in Canada to be the foundation for the 

development of effective area-wide strategies that promote the sustainability of the 

aquaculture industry. Ecosystem interactions with bivalve culture are highly complex as a 

result of potential effects on suspended particles, particularly in terms of food resources; 

sediment geochemistry and benthic habitat; nutrient cycling; and benthic and pelagic 

population and community dynamics. The number of fundamental ecosystem processes 

potentially influenced by mussels, and the complexity of their interactions, make it difficult 

to predict the effects of the culture on many ecosystem properties without resorting to a 

model. A combination of multidisciplinary field research and ecosystem modeling in 

intensively farmed Prince Edward Island (PEI) coastal embayment has been conducted to 

investigate ecological consequences of mussel filter-feeding, feces deposition, excretion and 

harvesting, and interactions between aquaculture and coastal eutrophication (nutrient 

pollution). This research has provided Canadian decision-makers with comprehensive 

science advice and is being used to develop approaches for assessing the capacity of 

ecosystems to support the future growth of the industry. 

Highlights from the Presentation: 

• A recurring bottleneck to the establishment of an operational framework for managing 

aquaculture is the need to define an "unacceptable" impact. 

• While science has an important role in advising managers and policymakers on the ecological 

consequences related to available management options, this decision needs to be made within 

an integrated framework that recognizes important linkages between ecological and 

socioeconomic systems. 

• An important consequence of developing an effective science-based management framework 

for aquaculture is that it will increase public confidence and reduce negative driving forces on 

industry. To achieve this goal, the development of a management framework should be 

inclusive, with diverse stakeholder participation, transparency, and communication. 

• Ecosystem research results have been used to make recommendations on indicators 

(measures of habitat and ecosystem status) and thresholds (predetermined impact limits used 

to trigger management actions) for use in assessing shellfish aquaculture impacts on marine 

habitat and to develop monitoring frameworks for assessing habitat effects of shellfish 

aquaculture. 

• A habitat assessment framework was recommended for shellfish aquaculture. The 

framework is based on a tiered monitoring approach recognizing that an increased risk to fish 

habitat requires an increased monitoring effort. 

• Ecosystem modeling provided the means for a quantitative assessment of the capacity of 

intensive mussel aquaculture to ameliorate impacts from excess nitrogen enrichment from 

land-use. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 13

Chronic Effects of Eutrophication on Bivalve Shellfish 

Dr. JoAnn M. Burkholder, North Carolina State University 

Although intensive shellfish aquaculture can cause localized degradation of water quality in 

some poorly flushed coastal regions, bivalve aquaculture in many areas is a minor contributor 

of pollutant loadings compared to land-based sources. In contrast, major, pervasive nutrient 

pollution from many urban and agricultural sources is seriously affecting shellfish 

populations and shellfish aquaculture, and these impacts are expected to increase with rapidly 

expanding coastal development. The National Research Council has reported that 60 percent 

of the coastal rivers and bays in the United States are moderately to severely degraded by 

nutrient pollution, mostly from land-based urban and agricultural sources. Coastal population 

growth worldwide and associated nutrient pollution are rapidly increasing. The acute, 

obvious effects of urban and agricultural nutrient pollution, often accompanied by microbial 

pathogens, are fish kills and high-biomass algal blooms. Much more serious chronic 

impacts, however, include long-term shifts in nutrient supplies; increased “dead zones” of 

low-oxygen bottom water; loss of critical habitat such as seagrass meadows; stimulation of 

harmful algal species that are low in food quality; reduction of shellfish recruitment and 

grazing; and increased shellfish physiological stress, disease and death. Increasing 

temperatures from present warming trends caused by climate change can interact with 

pollution to weaken shellfish hosts and facilitate pathogen attack. Considering that shellfish 

aquaculture is vital to meeting the seafood demands of the rapidly increasing global human 

population, there is a pressing need for resource managers and policymakers to increase 

protection of shellfish aquaculture operations from land-based nutrient pollution. 

Highlights from the Presentation: 

• Relative to land-based pollution sources, shellfish aquaculture contributes little to 

eutrophication (nutrient pollution) except in localized, poorly flushed areas along 

U.S. coasts. Aquaculturists should continue to strive to minimize these impacts. 

• There is a pressing need for resource managers and policymakers to increase 

protection of shellfish aquaculture operations from land-based nutrient pollution. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 14

Mussel Farming as a Tool for Remediation of Coastal Waters: Experiences from 

Sweden 

Dr. Odd Lindahl, Kristineberg Marine Biological Station, Sweden 

Nutrient emissions from agriculture, rural living, the atmosphere and many other diffuse 

sources increase coastal primary production leading to increased biomass in both filamentous 

algae and phytoplankton. Because phytoplankton is the main feed for mussels, mussel 

farming and harvest are been recognized as possible measures to improve coastal water 

quality. A cost-efficient and environmentally friendly way of taking care of diffuse nutrient 

emissions is the cultivation of mussels through the long-line farming method. When the 

mussels are harvested, a known amount of the nutrients are recycled back from sea to land, 

mainly in the form of valuable seafood or marine protein. One kg of live mussels will remove 

8.5 to 12 g of nitrogen, 0.6 to 0.8 g of phosphorous, and about 40 to 50 g of carbon. 

The ecosystem service provided by mussel farming has been recognized by Swedish 

environmental authorities as a possible measure to improve coastal water quality. The main 

principle is the implementation of nutrient trading as a management tool. This imposes 

demands on those who emit the pollution through emission quotas, which are traded and 

bought by the emitter. The seller is a nutrient harvesting enterprise (e.g., a mussel farmer). 

For example, in one trial between 2005 and 2011, the community of Lysekil, Sweden, was 

permitted to continue to discharge nitrogen from the sewage treatment plant, presupposing 

that the same amount of nitrogen was “harvested” and brought ashore by 3,900 tons of 

farmed blue mussels. The annual cost of $230,000 for Lysekil was far below the price for 

nitrogen removal in the sewage treatment plant. This payment goes to a mussel farming 

enterprise which has been contracted for the removal of 39 tons of nitrogen from the 

recipient waters annually. This is estimated to correspond to 100 percent nitrogen treatment 

of the discharges from the sewage treatment plant. 

Highlights from the Presentation: 

• Shellfish farming is a cost-effective, flexible, and environmentally friendly measure for 

combating eutrophication (nutrient pollution) and improving coastal water quality. 

• Shellfish farming is a sustainable way of producing healthy seafood while also recirculating 

nutrients from sea to land. 

• Nutrient trading is a useful management tool that connects environmental economy (nutrient 

discharges) with market economy (shellfish farming enterprises). 

• In the sea, shellfish farming has the same effect as open landscape feeding on land. Thus, 

“mussel farming - clear water feeding” will be a new slogan. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 15

Genetics of Shellfish, Wild and Farmed 

Dr. Dennis Hedgecock, University of Southern California 

Use of non-native species, reductions in biodiversity, and gene flow between domesticated 

farmed and wild stocks are potential genetic impacts of shellfish aquaculture. Although 

global shellfish culture is based on non-native species (e.g., the Pacific oyster Crassostrea 

gigas and the Manila clam Ruditapes philippinarum), the aquaculture industry, at least in 

Europe and North America, is not currently a major vector of new shellfish introductions. 

On the other hand, interactions of wild and farmed shellfish stocks deserve greater attention 

and research support at a global scale. Aquaculture in general, and shellfish culture in 

particular, lack domesticated strains and rely largely on hatchery propagation of wild stocks. 

The legendary high fecundity of bivalve molluscs (females can typically spawn tens of 

millions of eggs at one time) creates a risk that hatchery-propagated shellfish stocks could 

dilute the genetic diversity of wild populations and possibly elevate the frequency of harmful 

mutations. Continued farming of wild, native species will raise rather than lower these risks 

over time. Moreover, farming wild animals is a less efficient food production system than 

one based on domesticated stocks with improved traits, increased production efficiency, and 

reduced environmental and energy footprints. Yet use of genetically divergent domesticated 

stock might also increase the risks of detrimental effects on the genetics of wild populations. 

Farming triploid bivalves, which are largely sterile, essentially eliminates genetic interactions 

with wild shellfish. However, since tetraploid bivalves are used to generate triploid seed and 

tetraploids are self-fertile, the bio-security of tetraploid stocks becomes a new issue for 

study. Research on developing and improving domesticated shellfish for aquaculture and on 

improved methods for eliminating interaction with wild populations (bio-security) should 

have high priority for research leading to sustainable management of shellfish resources. 

Highlights from the Presentation: 

• Research on developing and improving domesticated shellfish for aquaculture and on 

improved methods for eliminating interaction with wild populations (biosecurity) should have 

high priority for research leading to sustainable management of shellfish resources. 

• Although non-native species are widely used in shellfish aquaculture, as in agriculture, 

shellfish aquaculture is probably not currently an important vector of new introductions. 

• Interactions of wild and farmed shellfish deserve greater attention because they could be 

detrimental to both. 

• Farming of wild stocks may, over time, increase the likelihood of detrimental interactions. 

• Farming of domesticated stocks permits genetic improvement but may elevate the risk of 

detrimental interactions with wild stocks. 

• Farming of triploid domesticated shellfish, which are effectively sterile, permits genetic 

improvement while greatly reducing or eliminating negative interactions with wild stocks; 

containment of fertile tetraploids is an issue deserving closer attention. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 16

Marine Invaders and Aquaculture: Sources, Biodiversity, Impacts and Consequences 

Dr. Dianna Padilla, Stony Brook University 

Aquaculture – both private commercial and public stock enhancement – is a leading source 

of introduced non-native species in marine and estuarine waters, second only to shipping. 

Many initial introductions are historic, but new introductions—the aquaculture species 

themselves and associated macro- and micro-species, including agents that cause disease—

continue to invade and spread on shores around the world. Aquaculture escapees, especially 

bivalves, can have large ecological impacts on shores, hybridizing with and displacing 

important native species. Safe introductions (i.e., introductions that do not escape and 

spread) are rare. The time lag between when a species is first introduced and when it begins 

to spread is unpredictable, and can be short (a few years) to very long (>75 years). Our 

ability to predict the impacts of invaders is poor, but many can have devastating impacts on 

local populations of commercially and ecologically important species and communities, 

including marine reserves and protected areas. For example, the Pacific oyster, Crassostrea 

gigas, is now a major introduced species spreading on shores in North America, Australia, 

and Europe. Many marine invaders impose significant negative impacts on aquaculture 

species (e.g., disease, bloom forming harmful algae, and direct fouling) and the aquaculture 

industry (e.g., through fouling gear). Due to the substantial ecological harm and economic 

costs that can be caused by introduced species and the unpredictable nature of predicting 

which species will be invaders, when they will spread, and what impacts they will have, a 

risk-averse strategy will be the safest course when considering new aquaculture 

introductions. All safeguards should be in place to ensure that non-native species are not 

transferred or likely to escape culture through aquaculture practices. 

Highlights from the Presentation: 

• Aquaculture is the second leading source of non-native introduced species in marine 

systems. 

• Invaders include aquaculture species themselves as well as associated macro- and 

micro-species, including disease causing agents. 

• Spread can occur decades after initial introductions, and the timing and impacts of 

spread are often impossible to predict. 

• Care must be taken to prevent the introduction and spread of non-natives through 

aquaculture, including consideration of new aquaculture species and aquaculture 

locales for non-native species. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 17

Effects of Environment and Culture Techniques on Shellfish Disease Severity and 

Prevalence 

Dr. Roxanna Smolowitz, New England Aquarium 

Disease is the result of the interaction of three factors: host susceptibility, agent virulence, 

and environmental conditions. Elimination or modulation of any one of these factors can 

decrease or increase the occurrence of disease in a host. When disease occurs in a molluscan 

population, our lack of understanding of why the disease happens and how, causes us to treat 

the disease as though it is a black box. But because disease is a combination of factors, if we 

logically think about the factors and then begin our investigations on the pathogenesis by 

examining important factors, we can develop an understanding of the disease as well as 

methods to prevent or manage around it. Factors important in disease occurrence are 

summarized below. 

Highlights from the Presentation: 

• Host susceptibility (i.e., poorly conditioned animals and genetic lack of disease 

resistance). 

• Agent virulence (i.e., new or mutated agent in the environment; change in the base 

population level of agents, such as increased density of the agent; direct vs. indirect 

infections). 

• Environmental conditions (i.e., density of the host; pollution; decreased water quality; 

decreased nutrients; and temperature/salinity/pH changes of the water). 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 18

Importance of Bivalve Molluscs: The Habitat They Generate and Associated Ecosystem 

Services 

Dr. Loren Coen, Sanibel-Captiva Conservation Foundation 

Aquaculture is making an ever-increasing contribution to meeting the worldwide demand for 

shellfish, as native wild stock (captured) populations decline. At the same time, recently we 

have become more aware of the ecosystem services provided by native bivalves as habitat, 

biofilters, and shoreline stabilizers. These bivalves occur as reef-forming, aggregationforming, or shell-accumulating species. Given the significant decline in native species 

populations, the loss of all critical (nursery) habitats, and the increasing worldwide 

contribution of cultured native and non-native species, we need to examine and critically 

evaluate their value and impacts. These include positive and negative, direct and indirect, 

biotic and abiotic effects in estuarine and marine systems. For the United States these 

impacts currently vary by location of habitat (intertidal vs. subtidal), extent of cultured vs. 

natural acreage, and 3) by latitudinal/geographical differences (e.g., western Atlantic/Gulf of 

Mexico vs. Eastern Pacific). 

Highlights from the Presentation: 

• Aquaculture can provide enhanced habitat for natural communities. 

• Culture of native species can reduce the fishing pressure on native wild stock. 

• Methodologies to assist with native species restoration should be used (e.g., Olympia 

oyster). 

• Sustainable practices need to be investigated, developed, and implemented. 

• Greater emphasis needs to be placed on quantifying the impacts, both positive and 

negative, of large-scale bivalve aquaculture. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 19

Assessing the Impacts of Shellfish Aquaculture Harvest: Lessons Learned 

Dr. Bradley P. Harris, University of Massachusetts – Dartmouth; Dr. Kevin D. E. 

Stokesbury, University of Massachusetts – Dartmouth; and Dr. Edward P. Baker, University 

of Rhode Island 

 

As the shellfish industry expands, growers, managers, and permitting agencies will face 

increasing pressure to demonstrate that harvest activities are environmentally benign. 

Drawing causal connections between environmental changes and harvest activities requires a 

formal experimental design and representative sampling at appropriate temporal and spatial 

scales. The Before-After Control-Impact (BACI) experimental design provides a framework 

for testing these harvest-impact hypotheses. We conducted a BACI assessment of sea scallop 

(Placopecten magellanicus) dredge harvest and found that changes in the epibenthic 

community were similar between the control and impact areas. Further, annual substrate 

composition changed more than epibenthic faunal composition, indicating high levels of 

natural disturbance—which may explain why harvesting did not alter the benthic community. 

Lessons learned and guidelines for conducting a BACI study include: 

• Use a pilot study to select the temporal and spatial sampling scales. 

• Select a sampling design adaptive to new technologies. 

• Incorporate/anticipate spatial and temporal variability. 

• Use sampling techniques that develop your intuition of the ecosystem (automation 

can kill intuition). 

• Start as simply as possible and build a mosaic. 

Most importantly, absolute measures sampled in the units of the expected impact are required 

to explain changes in a population, community, or ecosystem due to harvest activities. 

Highlights from the Presentation: 

• Cause and effect hypotheses require experimental design; the BACI design is ideal 

for testing the connections between harvest activities and environmental changes. 

• Establish the appropriate temporal and spatial sampling scales. 

• Anticipate spatial and temporal variability; natural disturbance provides a context for 

determining if harvest activities have adverse impacts. 

• Avoid collecting relative samples; absolute measures, sampled in the units of the 

hypotheses, are required to explain anthropogenic changes in a population, 

community, or ecosystem. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 20

Case Studies–Perspective: Education and Engagement 

Dr. Gary Jensen and Dr. Jeff Silverstein, U.S. Department of Agriculture 

The advancement of shellfish aquaculture depends on the generation of new discovery 

information and access to our collective knowledge system supported by public investments 

in science, technology and education, and private sector innovations. The United States has 

two university-based programs with an informal education mission founded on science. 

Numerous land-grant universities and sea grant institutions—in partnership with the USDA 

Cooperative State Research, Education and Extension Service and the NOAA National Sea 

Grant Office, respectively—have programs aimed at assisting the U.S. farmed shellfish 

sector. These same university programs also support research projects and interact with 

federal research partners—the USDA Agricultural Research Service and NOAA. 

The winds of change are affecting shellfish aquaculture businesses. This situation implies 

new approaches and actions by the shellfish aquaculture community focused on the transition 

from science to practice. This presentation highlighted several case studies as examples of 

the benefits of research-extension integration, engagement, and education: seafood Hazard 

Analysis and Critical Control Point (HACCP) alliance for education; aquaculture effluents 

task force; national organic aquaculture work group; and Viral Hemorrhagic Septicemia 

(VHS) education alliance. Each case study is based on scientific information generated from 

highly relevant solution research and mobilizing expertise across states and institutions with 

a common purpose to address an industry-critical issue or need. To leverage resources, 

engage broader extension expertise, and strengthen state-federal partnerships, the USDA 

Cooperative State Research, Education and Extension Service and NOAA’s National Sea 

Grant Office established the National Aquaculture Extension Steering Committee. This 

interagency action has resulted in new collaborations and projects to support the aquaculture 

extension community and its educational role of advancing industry development. 

Highlights from the Presentation: 

• If it is not business as usual in the industry sector, federal and state research and 

educational programs should seek effective approaches that take full advantage of our 

knowledge system, expertise, and limited resources through effective collaborations 

and partnerships. 

• There are numerous examples of participatory processes, engagement, and strategic 

actions that have addressed complex regional and national issues that can serve as 

models for other applications and issues. 

• New tactics and bold steps may be required to reach a desired future state, including 

development of effective collaborations and partnerships that may extend outside of 

the United States. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 21

World Wildlife Fund Molluscan Shellfish Dialogues 

Colin Brannen, World Wildlife Fund-U.S. 

Through a series of roundtable discussions known as ‘Aquaculture Dialogues’, the World 

Wildlife Fund (WWF) works with seafood farmers, retailers, NGOs, scientists, and other 

aquaculture industry stakeholders worldwide to develop global standards for certifying 

aquaculture products. Certification is understood to mean that the product is grown and 

harvested in an environmentally and socially responsible way. The goal of aquaculture 

certification standards is to minimize key environmental and social impacts associated with 

seafood farming. Dialogues are under way for 12 marine and freshwater species, including 

tilapia, salmon, shrimp, molluscs, trout, and pangasius. 

Highlights from the Presentation: 

• Currently, more than two dozen standards or certification programs for aquaculture 

exist. Most are ineffective at helping make the global aquaculture industry more 

sustainable. 

• The standards created by WWF’s Aquaculture Dialogues will be created by a broad 

and diverse set of stakeholders, based on consensus, developed through a transparent 

process, science-based, measurable, and performance-based. 

• The WWF Aquaculture Dialogues build from previous work done by the 

organization, including the Forestry Stewardship Council, the Marine Stewardship 

Council, Protected Harvest, and the Climate Savers Program. 

• To date, the WWF Molluscan Dialogues have attracted 235 participants from nine 

countries. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 22

Shellfish Aquaculture and the Sustainable Seafood Movement 

Dr. George H. Leonard, The Ocean Conservancy 

Sustainability is the intersection of the environmental, economic, and societal sectors. 

Presently, the sustainable seafood movement, of which farmed seafood products is a part, is 

generally focused only on the environmental aspects of this concept. The sustainable seafood 

movement includes four components: eco-certification, consumer education, single species 

campaigns, and partnerships among businesses and NGOs. 

 

Highlights from the Presentation: 

• Several key issues contribute to overall environmental sustainability, including use of 

marine resources for feed; impacts of escaped fish; amplification and retransmission 

of disease and nutrient pollution; and other habitat impacts. 

• Shellfish farming is generally viewed favorably because it requires no supplemental 

feed, has limited pollution impacts, and lower risks of escapes because animals are 

generally sedentary. 

• Going forward, the shellfish industry needs to be concerned with questions of science 

and society. 

• Important questions remain to be answered surrounding the local impacts of harvest 

methods as well as broader questions of what scale of farming is compatible with 

overall ecosystem health and function. 

• Addressing the societal questions is likely to pose the toughest challenge. For 

example, much of the current controversy surrounds issues of what people see – or 

are willing to look at – from their waterfront property (this is also known as 

‘viewshed’), property rights, and the future use of habitats which can be viewed as 

public trust resources. 

• Geoduck farming is one example of the broader need for a national dialogue on the 

future role of aquaculture in our nation’s coastal and ocean ecosystems. 

• As competing interests in our nation’s oceans grow—including interest in 

aquaculture—a multi-stakeholder approach holds promise for resolving these 

inevitable conflicts and for crafting a forward-looking vision for both sustainable 

ocean economies and the healthy ocean ecosystems on which they depend. 

 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 23

Thoughts on the Environmental Concerns with Molluscan Shellfish Aquaculture 

Development 

Dr. Gary H. Wikfors, NOAA Northeast Fishery science Center – Milford Lab 

Concerns about possible environmental impacts of shellfish aquaculture range from changes 

in ecosystem structure and function to pollution and multi-user conflicts. These concerns 

often are viewed as proscriptive, for example, when people say, “We can’t let that happen.” 

However, we live with many of these environmental changes as consequences of other 

human activities. Many examples are from land-based, agricultural production of human 

foods, but environmental modifications in the marine environment to accommodate 

recreation, capture fisheries, and transportation of goods are ubiquitous. It is unrealistic to 

expect farming of any kind to not modify the surrounding environment; nevertheless, 

concerns about impacts often are presented as barriers. 

 

Assumptions underlying tacit intolerance of potential shellfish–aquaculture impacts on 

coastal areas can be questioned. Most coastal waters where shellfish aquaculture expansion 

can occur are not pristine wilderness areas; most are highly impacted by other human 

activities. In fact, a major concern is whether coastal areas have sufficient environmental 

quality to sustain shellfish growth. The perception of shellfish aquaculture as an industrial 

activity that will benefit a few at the expense of the general populace is challenged by the 

reality that shellfish farming often is local, place-specific food production consistent with the 

current movement toward local foods and community-supported agriculture. Thus, changing 

perceptions about environmental and societal aspects of shellfish farming are revealing this 

activity to be consistent with the ecosystem services desired by human communities from 

their coastal seas. The way forward for molluscan shellfish aquaculture is complex but 

achievable. 

Highlights from the Presentation: 

• Put perceived risks in a realistic context. 

• Question the assumptions underlying barriers. 

• Recognize evolution of societal values. 

• Benefit from the opportunity to do it right/better. 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 24

Appendix 1 

MONDAY, JUNE 9, 2008 

8:00 - 8:15 a.m. Welcome

Dr. Sandra Shumway, University of Connecticut 

8:15 - 8:45 a.m. Opening Remarks

Timothy R. Keeney, NOAA Deputy Undersecretary for Oceans and 

Atmosphere 

Dr. Michael Rubino, Manager, NOAA Aquaculture Program 

Brian Pawlak, Deputy Director, NOAA Office of Habitat Conservation 

Eutrophication/Carrying Capacity/Water Quality

8:45 - 9:00 a.m. Dr. Jon Grant (Dalhousie University) 

· Shellfish Culture in the Realm of Ecosystem-Based Management

9:00 - 9:15 a.m. Dr. Peter Cranford (Fisheries and Oceans Canada) 

· Ecosystem Interactions with Intensive Mussel Aquaculture: Research 

Applications

9:15 - 9:30 Open Question Period 

9:30 - 9:45 a.m. Dr. JoAnn Burkholder (North Carolina State University) 

· Chronic Effects of Eutrophication on Shellfish

9:45 - 10:00 a.m. Dr. Odd Lindhal (Sweden’s Kristineberg Marine Biological Station) 

· Shellfish Farming as a Tool for Remediation of Coastal Waters 

10:00 - 10:15 a.m. Open Question Period 

Genetics/Invasives/ Disease 

10:45 - 11:00 a.m. Dr. Dianna Padilla (State University of New York - Stony Brook) 

· Marine Invaders, Biodiversity & Aquaculture: Sources, Impacts & 

Consequences

11:00 - 11:15 a.m. Dr. Dennis Hedgecock (University of Southern California) 

· Genetics of Shellfish, Wild and Farmed

11:15 - 11:30 a.m. Dr. Roxanna Smolowitz (New England Aquarium) 

· Effects of Environment & Culture Techniques on Shellfish Disease 

Severity & Prevalence

11:30 a.m. - 12:00 p.m. Open Discussion with Entire Group 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 25

MONDAY, JUNE 9, 2008 (continued) 

12:00 - 12:30 p.m. Guest Speaker – U.S. Senator Jack Reed (Rhode Island)

Afternoon Breakouts (Facilitated Discussions) 

1:30 - 2:15 p.m. Eutrophication/Carrying Capacity/Water Quality 

2:15 - 3:00 p.m. Invasives/Genetics/Disease 

3:30 - 5:00 p.m. Summary Presentations and Discussion 

5:00 p.m. Adjourn 

TUESDAY, JUNE 10, 2008 

8:00 - 8:15 a.m. Day 2 Welcome

Dr. Sandra Shumway, University of Connecticut 

Habitat and Gear/ Education/ Societal Interactions/ Engagement

8:15 - 8:30 a.m. Dr. Loren Coen (Sanibel-Captiva Conservation Foundation) 

· Importance of Bivalve Molluscs: The Habitat they Generate and 

Associated Ecosystem Services 

8:30 - 8:45 a.m. Dr. Kevin Stokesbury (University of Massachusetts - Dartmouth) 

· Impacts of Shellfish Aquaculture Harvest Methods 

8:45 - 9:00 a.m. Open Question Period 

9:00- 9:15 a.m. Dr. Gary Jensen (USDA-CSREES) 

· Case Studies and Perspectives: Education and Engagement in 

Aquaculture 

9:15 -9:30 a.m. Colin Brannen (World Wildlife Fund) 

· Molluscan Dialogues Revisited 

9:30 - 9:45 a.m. Dr. George Leonard (Ocean Conservancy) 

· Shellfish Farming and the Growing Sustainable Seafood Movement 

9:45- 10:00 a.m. Open Question Period 

10:30 - 10:45 a.m. Dr. John Hargreaves (Baton Rouge, Louisiana) 

· BMPs & Environmental Management Systems in Shellfish Aquaculture 
Summary of the 2008 NOAA National Symposium on Shellfish & the Environment 26

TUESDAY, JUNE 10, 2008 (continued) 

10:45 - 11:00 a.m. Dr. Gary Wikfors (NOAA, Northeast Fisheries Science Center) 

· Thoughts on the Environmental Concerns with Molluscan Shellfish 

Aquaculture Development 

11:00 - 11:15 a.m. Dr. Susan Stonich (University of California - Santa Barbara) 

· Societal Issues Associated with Shellfish Aquaculture 

11:15 a.m. - 12:00 p.m. Open Discussion with Entire Group 

Afternoon Breakouts (Facilitated Discussions) 

1:30 - 2:15 p.m. Gear and Harvest/ Education 

2:15 - 3:00 p.m. Societal Interactions/ Engagement 

3:30 - 5:00 p.m. Summary Presentations and Discussion 

5:00 p.m. Adjourn