Background Research & Analysis

In the summer of 2012, a Shellfish Viability Test was conducted by the town to demonstrate initial feasibility. A complete write-up of this milestone is included as OP-TM-2. This Test included the following test methods and results:
  • 3 oyster bags in Green Pond
  • 3 oyster bags in Little Pond
  • Gear was donated by a local oyster grower
  • Initial test accomplished by volunteers
  • Oysters destroyed at end of test
  • Oysters examined weekly
  • Oysters tested for health/disease
  • Survival/growth measured at end
  • Use of oysters as the shellfish for the viability test
  • Work was under the direct oversight of the town through the Shellfish Constable

Results


While the expectation was that there will be roughly a 50% survival rate, the results of the viability study show much lower mortality rates (only 1 out of 1,247 individuals). This is likely due to a combination of factors: good husbandry, resilient genes, lack of predation, and low stocking densities. Subsequent disease testing of a sample of the Little Pond oysters revealed no MSX or Dermo. Part of the finding of the Demonstration will be an assessment of the mortality of larger-scale oyster cultivation. Based on the success of this test, the town hired Woods Hole Group to assist with the planning for this project. Their research and analysis can be accessed by clicking on the titles below. These reports include:
  • Stock Assessment Report
  • Little Pond Viability Test
  • Literature Review and Discussion of Findings
  • Project Planning, Specifications and Cost Estimates
The Stock Assessment Report and Little Pond Viability Test Review (OA-TM-1) confirmed that oysters are likely to survive and grow in Little Pond.

Considered Species


Selecting oysters from the range of options available was based on the information provided in OA-TM-2. The following species of shellfish were considered:
  • Bay Scallops (Argopecten irradians)
  • Mussels (Mytilus edulis)
  • Oysters (Crassostrea virginica)
  • Quahog Clams (Mercenaria mercenaria)
  • Ribbed Mussels (Geukensia demissa)
  • Soft Shell Clams (Mya arenaria)
In addition to the nitrogen assimilation capacity, of particular importance to species selection, was the likelihood of grow-out success. Once oysters were chosen, the data on nitrogen removal and cost were carefully considered by the WQMC.

Variables


Several key variables significantly impact the cost and nitrogen-removal of shellfish, including:
  • Gear choice (floating bags or submerged cages)
  • Initial number of seed (0.5M, 1.0M, 1.5M 2.0M)
  • Nitrogen-removal capacity as percent of total N load
  • Seed starting size (2mm, 6mm, 12 mm, 18mm)

Criterion


A critical Demonstration criterion is to be able to measure a change in nitrogen in the water after oyster installation and growth. The total nitrogen load for Little Pond came from the Little Pond Massachusetts Estuaries Project (MEP) Final Report (2006). In addition, a model calculation of the likely daily mass of nitrogen that would be present in the water column was developed. These values and information on the standard deviation of the data in the MEP Report for Little Pond were compared to validate that the quantity and starting size of oysters could remove a mass of nitrogen that is likely to be measurable through each growing season over the 3-year project duration. In particular, the percentage change of nitrogen over seasonal (May-October) load when the MEP studies indicated the nitrogen Sentinel Threshold would need to be achieved and daily flux were used as the basis for determining how many oysters to grow in order to be able to measure a change in nitrogen concentration. For the colder months of the year, the MEP reports indicated that dissolved nutrients in the water would be of little consequence to the health of the ecosystem since there is relatively low or negligible biological activity in the estuaries during that mostly dormant period. Tables 1, 8, 9, 12, and 13 in OA-TM-3 present the values for percent nitrogen removal for the warmer months of the year. Scenarios for intermediate seed start-size were also evaluated. The specifications and a cost estimates for the Demonstration for three years included seed, gear and labor costs organized by varying quantities of seed of different starting size. Tables 2-7 and 11, found in OA-TM Number 3, present this cost information.

Issues


The WQMC identified several issues that needed to be balanced in the final design of the Demonstration, evaluating a number of different implementation scenarios to fit within the following constraints:
  • Area/Aesthetic Constraints and Competing Uses of Little Pond for Paddling and Passive Enjoyment
  • Economic/Budget Constraints
  • Permitting Requirements and Compliance
  • Scientific Constraints - The Need for Measurable Results Over Statistical Variations in Background Nitrogen

Final Design


The final design came through an iterative process of discussion and analysis. Input from a broad range of stakeholder groups was also carefully considered. These groups include Division of Marine Fisheries (DMF), Department of Environmental Protection (DEP), Falmouth Department of Natural Resources (now the Department of Marine and Environment), Falmouth Conservation Commission (ConCom), local community members and abutters, local shellfish growers and commercial harvesters, the town of Mashpee Shellfish Constable, and several individuals who have either interest in, or experience with shellfish cultivation and nitrogen bioextraction methods. While the plan was developed with the intent that the Demonstration will be managed by the town, the advantages and disadvantages of a town-sponsored versus private aquaculture grant was also assessed.

Shellfish aquaculture was not considered in the 2009 Alternatives Screening Analysis Report. It is now a key demonstration project in this CWMP. The Monitoring Plan for this Oyster Aquaculture Demonstration Project (Demonstration) ensures careful tracking of costs and water quality improvements. If it proves to be a successful nitrogen management method, the CWMP will be modified through adaptive management to incorporate shellfish aquaculture more broadly in the planning area.

Parameters to be Measured


Parameters to be measured include:
  • Benthic condition (periodical)
  • Chlorophyll-a
  • Dissolved oxygen
  • Orthophosphate
  • pH
  • Pheophytin-a
  • Salinity
  • Temperature
  • Total nitrogen
    • Ammonia
    • Dissolved Organic Nitrogen
    • Nitrate
    • Nitrite
    • Particulate Organic Nitrogen
  • Transparency (Secchi depth)
  • Other parameters as specified in the Quality Assurance Assessment Plan, as well as shellfish weight (periodic)