Tisbury Great Pond Oyster Hatchery

On Tisbury Great Pond Tom Osmers tends thousands of healthy seed oysters in the oyster nursery. The seed are part of a larger effort by Martha's Vineyard Shellfish Group to build sustainable hatcheries here.

Even though Tom says his efforts "all are for beauty," there is a need to be on guard. Flowing through Oysters are nutrients, minerals and oxygen, and potentially Dermo, an invasive parasite.

Osmers checks on the young oysters as they find something to attach to and grow. Pea-size oysters float in sacks held on the surface by kid's floaties. Other beds made of plastic deer fencing hold older oysters stuck to scallop shells.

Dermo is an oyster parasite that attacks its gut. (It doesn't harm humans or alter the flavor of the meat,) but it eats the food the oyster eats, and slowly starves it. Oyster populations from Maine to the Chesapeake Bay have been affected by Dermo, and hatcheries up and down the coast have at one time or another had losses of up to 90% of their stock to Fermo and other diseases.

5 years ago Dermo nearly wiped out the entire oyster population in Tisbury Great Pond. These new seed are 20% more resistant to Dermo, and hopefully will help build up Dermo resistance here, and restore the population to the numbers before the last parasite outbreak...

The seed oysters here were produced in the Martha's Vineyard Shellfish Group hatchery. They are from a Dermo-resistant broodstock that were in Edgartown Great Pond and are survivors of a Dermo epidemic there.

After more than a decade of exposure to Dermo, the Edgartown Great Pond oyster population has evolved, and their offspring have developed a resistance to the parasite.

The floating nursery beds are strung out in a train. The mesh needs to be cleaned, and the beds flipped to allow for consistent sun and water flow. The train of beds can be blown by the wind causing their anchorages to crawl and must be drawn up away from shore. It's work.

But, it's not just Dermo that must be watched. These ponds are natural systems under significant strain and change. Although oysters can handle a certain amount of nutrients, in the form of nitrogen run-off for example, they do suffer quickly from systemic changes.

Increases in water temperature, and algae, and larger green crab populations, and changes in oxygen and salt levels in the water effect oysters. The oysters are part of a much larger natural ecology, and in order for the oysters to be healthy the whole pond must be tended to as well.

Green crabs eat the seed. In Menemsha Pond alone thousands of crabs are collected each year. The timing of the cut to the ocean is important to let Tisbury Great Pond flush and balance its salt level. The pond's water level must be right to push the cut open. This year the cut was a little later than usual. Interpreting the pond's dynamic system in the midst of change is a bit of a science, particularly when fewer people are working the beds for a living.

In the midst of all this flux, Tom Osmers says he's had to become what he calls an "entropologist." He's had to study change itself. Three more years, and we'll see if changes here, including the oyster seeding project, help to re-establish a sustainable oyster population and robust fishery.