Survey Says! What is the value of Greenwich’s shellfish?

A NOAA Fisheries research vessel, the R/V Victor Loosanoff, will be in Greenwich waters from Monday, Oct 1 through Friday, Oct 5, to allow scientists to conduct a shellfish population survey.

This survey is an important piece of an ongoing study which will provide the town, and particularly shellfish growers and harvesters, with data on the value of shellfish beyond the seafood market.

The study will also yield a methodology that other coastal communities can follow to quantify the economic value of environmental benefits provided by shellfish.

Shellfish such as hard clams and oysters feed by filtering algae and other organic material from the local environment. These suspension-feeding animals incorporate nutrients from their food into their own tissue and shell as they grow. Their feeding activity leaves water cleaner and clearer. Studies have shown that filter feeding shellfish can improve water quality in coastal areas that have excess nutrients and an overabundance of algae.

The NOAA Fisheries Milford Lab has a long history of conducting applied research to address questions of importance to communities and the shellfish aquaculture industry. Scientists at the NOAA Fisheries Milford Lab contributed to a recent project that modeled nutrient removal from Long Island Sound waters by Connecticut’s oyster industry and calculated what this nutrient removal service would cost if it was provided by traditional nutrient reduction strategies, such as wastewater treatment.

The Milford Lab is now working on a pilot study to document the local environmental benefits provided by shellfish by measuring and modeling nutrient capture and water quality improvements provided by clams and oysters in Greenwich. Collaborating with the Greenwich Shellfish Commission, a NOAA scientist focused on mathematical modeling, and a Stony Brook University economist, they are using a multidisciplinary approach to assign value to the environmental benefits of natural and aquacultured shellfish. Greenwich is a good model for investigating the benefits of shellfish; the town has a long tradition of shellfish cultivation, has committed to active shellfishing management, and has improved its water quality substantially in recent years.

To complete a comprehensive valuation of Greenwich’s shellfish resources, the research team had to develop the methods to collect a reliable population estimate for all of the clams and oysters in Greenwich waters. With help from the Greenwich Shellfish Commission, the team connected with local Greenwich oyster growers and integrated their use of commercial shellfish resources into the model. The growers provided estimates of population density, types of gear used, and mortality rates for the commercial leases.

In the current phase of this project, the research team will conduct a five day shellfish survey across Greenwich in October.

During the survey, scientists will sample from more than a hundred randomly selected stations spanning all types of shellfish areas (natural beds, commercial leases, etc.).

At each station, they will take a take a one-foot-square sample from the seabed to a depth of about six inches. From the samples collected, scientists will be able to quantify the mean clam density across the entire Greenwich seabed, map the relative density of clams across the seabed, and measure the size distribution of clams. Obtaining clam population data across all habitat types is critical for generating a realistic model and accurately appraising Greenwich’s shellfish resources