Gouldsboro’s Shellfish Resilience Lab

Gouldsboro has begun work on its Shellfish Resilience Laboratory and will have it operational by this spring. Located in Bunkers Harbor, the Resilience Lab is not only a key element in Gouldsboro’s program to restore clam flats to productivity and sustainability, but will also collect data and develop know-how that other Maine communities can use to manage municipal shellfish operations as Maine’s climate changes.

Brief Background

Close-up of soft-shell clam seed in late fall prior to overwintering. Photo credit: Downeast Institute.
Close-up of soft-shell clam seed. Photo credit: DEI

Green crabs have been eating soft-shell clams on the coast of Maine since the early 1900s. But as water temperatures in the Gulf of Maine have risen and as winters have become milder, green crabs are growing more quickly and more of them are surviving the winter. With more crabs eating clams, the population balance between crabs and clams has shifted dramatically, and there are fewer clams to harvest (See posts on this site about Green Crab and Soft-shell Clam lifecycles.) However, Gouldsboro and other communities have had success in using a combination of clam seeding and predator exclusion to restore flats to productivity. Clam seeding involves placing tens of thousands of one-year old clams (see the picture at right) on the clam flats. Predators (primarily green crabs, but also seagulls and others) are excluded by placing nets over the newly seeded clams.

 

Hatchery-reared soft-shell clam seed at DEI resting on window screening. Gouldsboro would grow these clams until they are large enough to put out on the clam flats. Photo credit: DEI
Hatchery-reared clam seed of the size that Gouldsboro purchase and grow. Photo credit: DEI

Use of clam seeding in Gouldsboro and other small communities is limited by the cost of purchasing one-year old clams, which currently cost $25 per 1,000 clams from the Downeast Institute (DEI). In response, and with support from DEI, Gouldsboro decided to explore the possibility of purchasing very young clams (< 2 mm shell length) in the early spring, not long after they are hatched. The cost would be about one-third that of the year-old clams. The town would then grow the clams over the summer, keep them alive over the winter, and use them the following spring.

DEI not only runs the hatchery that produces the juveniles, but also have already figured how to grow first-year clams over the summer and keep them alive over the winter. So, we know it can be done at the scale of DEI’s operation. But, can we bring this process down to a community scale? And, if we can do that, does it work financially?

Those are the questions that Gouldsboro has set out to answer. DEI offered technical and other assistance, and three other organizations, the Maine Shellfish Restoration and Resilience Fund, the Maine Community Foundation, and the Schoodic Community Fund, provided financial support to get the program started. Schoodic Institute at Acadia National Park and the Town of Gouldsboro have also provided substantial in-kind support.

Growth Over the First Summer

Floating trays with black plastic covers to keep seagulls from poking through the mesh and preying on the growing clams inside the tray. Photo credit: DEI

Once DEI delivers the juvenile clams to Gouldsboro in the early spring, the town will place them in nursery trays that will float in a lobster pound or other place that is protected from waves.

The trays have a tough, tear-resistant layer of window screen on the bottom that allows water and nutrients to flow easily into the tray, providing plenty of food to support growth. A few periwinkles that are placed in each tray keep the screen free from algae that could obstruct the movement of water and nutrients.

Each tray can hold fifteen to twenty thousand clams. It is summertime and the living is easy, so the clams can grow from about 2 mm to a shell length between 12 and 15 mm by late fall. This is large enough to use as clam seed. But if the town put the seed out on the mudflats in the fall, many of the small clams would not survive the winter. So, Gouldsboro will bring the clams in from the nursery trays to keep them inside over the winter.

Overwintering

An overwintering cage. Clams in mesh bags will spend the winter on the shelves in running seawater.

This is where the expense and risk comes into the picture. Consequently, it is the primary focus of the Shellfish Lab, at least for the first few years of operation. We will not only set up the systems to support clams over the winter, but will also monitor all the costs of running those systems. We will do this not only to learn how to make the process more efficient and financially attractive, but also to have data that other towns can use if they decide to build systems of their own. We will also keep track of clam survival: what proportion of clams did we keep alive through the summer and what proportion make it through the winter?

To keep the clams alive over the winter, we will keep them in water that is cold, clean, and full of oxygen. DEI does this by putting the clams from the nursery trays into mesh bags that are placed on shelves in overwintering cages. The picture on the right shows one of the cages that Gouldsboro shellfish warden Mike Pinkham had built for this purpose. These cages and the tens of thousands of clams inside them will be submerged in a tank full of seawater that is constantly pumped in from Bunkers Harbor. Below is a picture of the tank that Dana Rice donated for use in the lab. Years ago, it was used at the lobster pound at Tidal Falls in Hancock. We will be giving it a new life and purpose.

Inside the future Shellfish Resilience Lab: the tank we will repurpose to overwinter clams.
Inside the future Shellfish Resilience Lab: the tank we will re-purpose to overwinter clams.

Next steps

If you look closely at the photo of the tank you might notice that the walls look like they are made of insulating board. Looks are not deceiving: the two rooms that Dana Rice provided for the Shellfish Resilience Lab are in his lobster operation in Bunkers Harbor. Years ago, these two rooms were full of ice and cooled by refrigeration units because they were the center of a clam buying and wholesaling operation. (We celebrate their return to use as part of the clam fishery.) All the walls are covered by 4 inches of foam board. Once we get the building sealed up, it should be easy to keep it at the cool temperatures that we need for the overwintering operation.

The next steps are to seal up the building, put wall coverings over the insulation, and install new electrical service. (Since the rooms were designed to be full of ice, they do not, for good reason, have outlets.) We will install pumps and pipes and plan to get the Shellfish Lab up an ready for initial test operations by spring. Mike Pinkham and Jim McLean, Gouldsboro’s Supervisor of Town Infrastructure, have already started getting the construction process underway.

Getting Students Involved

All CSI-Maine programs aim to connect science, community, and schools. As we describe in other posts on this site, work with students has been at the center of the CSI-Maine Shellfish Resilience program from the outset. Students were deeply involved in early design work for the nursery trays and other work connected to the Shellfish Resilience Lab. But COVID-19 came along and threw a wrench into what schools are able to do. This changed the options that are available for direct student engagement in building the lab and in fieldwork this coming spring. We are hopeful that will change sooner rather than later.

For many of the shellfish harvesters in Gouldsboro, involving the students is nearly as important as figuring out how to overwinter clams. They often tell us that they wish they had been able learn science while getting outdoors and doing work that matters. They also see bringing young people out on the flats and into the fishery as essential to sustaining it.

Consequently, having a place for students to work and learn has been central to our plans for the Shellfish Lab from the beginning. In the short term, we have funding to support students in building and programming the micro-controller systems that we will need to monitor the systems in the lab. That is work that we should be able to do remotely. Over the longer term, we hope to involve students in much of the operation of the lab.

Gratitude

When Gouldsboro, Schoodic Institute, and Sumner Memorial High School first began thinking about building a lab to explore the operation and economics of a community-scale program to grow seed clams, it seemed like a really good idea and one that we should be able make into reality if we planned carefully. COVID-19, together with the scarcity of waterfront locations to support this kind of work, took us by surprise. But, we are now finally moving forward and should have much that we can report over the coming months.

We want to express special thanks to Dana Rice for making space available to the town and its shellfish committee for this work toward sustaining a healthy municipal shellfish program. We thank the Maine Shellfish Restoration and Resilience Fund, the Maine Community Foundation, and the Schoodic Community Fund for the financial support required to build and run this experimental program. We also thank the Elmina B. Sewall Foundation for supporting Schoodic Institute’s work with communities and schools. The Shellfish Resilience Project is a central part of that work.

— Bill Zoellick
    November 5, 2020

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