NOAA/National Marine Aquaculture Initiative (NMAI): Environmental and Technical Assessment of Alternative Shellfish Production Methods

Purpose or Scope:

The past two decades have seen a rapid expansion of alternative and innovative methods for the cultivation of shellfish; however, there is little information on the effects of these practices on the surrounding environment. This project is assessing environmental and technical aspects of cage and bag-on-bottom, bag-on-rack or bottom suspended oyster and clam culture, and net-protected or enhanced clam culture methods.

All research is being conducted in collaboration with East and West Coast U.S. shellfish researchers and industry members. This research meets the high priority 2015 goal 3.2, "Ecological impacts (positive and negative) associated with shellfish growing and harvesting, should be documented, understood, and incorporated into the shellfish industry Environmental Management System (EMS). " This work satisfies the research priorities of the Northeast Regional Aquaculture Center and the East Coast Shellfish Growers Association.

Approach:

The overall research approach is to: 1) characterize and quantify the effects of alternative shellfish culture methods on eelgrass; 2.) assess and compare benthic infauna and epifauna species, juvenile salmonids, shrimp and crab diversity, density, and biomass within and adjacent to shellfish culture and reference sites; 3) determine sediment and water column interactions associated with culture method and compare with undisturbed conditions; 4) model carrying capacity, phytoplankton concentrations, and sedimentation for different submerged and floating aquaculture methods and planting densities.; and 5) evaluate existing culture methods in terms of environmental impact and develop recommendations and guidelines for modifications to existing growing methods in order to reduce adverse impacts, maximize positive environmental effects and improve production efficiency.

Progress and Results:

Characterize and quantify effects on eelgrass: Direct effect experiments were conducted at a field sites in eastern Long Island Sound, near Groton, Connecticut, and indirect effects were obtained using quantitative data on light levels at off-bottom culture field sites in Long Island Sound, CT and Puget Sound, WA. Analyses of collected data were conducted during the fall-winter period 2005-06. Conclusions from these experiments were as follows:

Quantify biological effects: Research was an assessment and comparison of fish and invertebrates species' diversity, density, and biomass across habitat types in shellfish aquaculture and control sites. Seasonal sampling was conducted to address the abundance and species composition of benthic fauna and flora for a variety of culture methods and control conditions. Samples were collected at low tide from randomly selected locations within/underneath and adjacent to netted and un-netted clam, oyster bag, oyster longline, and oyster rack plots. Additional samples were taken inside each clam bag to capture organisms residing inside. Epibenthic samples were taken from the surface of oyster and clam bags and netting and at control points. A selected suite of samples from each site were sorted and analyzed for species composition and abundance. Conclusions from the experiments were as follows:

Flow modeling: This task included: 1) the construction of three-dimensional flow models of the studied farming locations; 2) the formulation of special algorithms to estimate shellfish growth based on rates of food uptake; and 3) the use of particle tracking algorithms to determine the fate of suspended solids produced by the aquaculture activities. Small scale, numerical flow models were used to calculate flow patterns within different types of aquaculture gear. These models were developed within the framework of the FLOW-3D software system. FLOW-3D is a Computational Fluid Dynamics (CFD) software package designed to analyze complex flows. The completed numerical models provided a quantitative framework from which the impact of different alternative shellfish culture practices were compared.

Outreach and reporting: The goal of the outreach program was to provide stakeholders with the knowledge to make informed decisions about shellfish aquaculture siting in the coastal environment. The principal element was presentation of the results to farmers and resource managers, and development of manuscripts for peer review. In addition, a comprehensive online database on shellfish aquaculture and the environment was developed and maintained by the Pacific Shellfish Institute.

A number of presentations about project results were made at regional meetings. The presentations listed below can be viewed in PDF format (file sizes are indicated):

Project Partners:

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