European Oysters at the Downeast Institute, Beals Island, Maine

The European oyster, flat oyster, belon, or mud oyster all refer to the bivalve Ostrea edulis, native to western Europe and introduced into Maine waters near Boothbay Harbor in 1949. Ask a true oyster gourmand and they will call it the best oyster available globally. Ask someone who's got some experience growing them, or working with them in the hatchery, and you'll get a mix of smiles, gritted teeth and a downright Eeyore gloom. In the oyster kingdom, flat oysters have to be most persnickety, mysterious and tantalizing variety out there.

The European industry has fallen (forgive me) flat, and the production from the East Coast of the US and Canada is not going to take the world over, despite tries from very inventive and persistent folks. Ditto for the west coast, and there are two main reasons for this. The first is that a parasite called Bonamia, which affects the hemocytes (blood cells) of the oyster, and is responsible for periodic die-offs of wild and cultured flat oysters: an intimidating enough obstacle. The second – and the reason for this post – is that they are often troublesome in the hatchery.

Some of the juvenile flat oysters produced at DEI. 

Chris Bartlett photo.

Many oyster species are broadcast spawners, meaning that sperm and eggs are released directly into the water, in hopes that the one finds and fertilizes the other. But oh no, that's not good enough for the flat oyster. They have to go and be different, to the point that the female holds on to the eggs, and allows them to be fertilized by sperm in the incoming water. Then, she even goes so far as to allow the embryos to develop for a while attached to her gills, before then ejecting them as free-swimming larvae. Added to this the complexity, is the life-cycle of Ostrea being a “protandric hermaphrodite.” That is, this oyster has the capacity to change its gender twice during a single season – spawning as a female, then changing to a male for a while, then back again! All this causes a lot of difficulty for the hatchery manager, who needs to reliably produce millions of oyster larvae to be financially solvent.

Meanwhile, there is a limited supply of flat oysters to meet the demand, and even though demand is not as large as for say, the Eastern oyster, it's a dedicated following, and there is money to be made for them's that can grow and market the right product.

Which brings me to the Downeast Institute (DEI), on Great Wass Island in the town of Beals, Maine; and the name says it. You come out hear, dear (they say 'heah' and 'deah' of course – music to my Mainer ears), and you have indeed arrived Down East.

Dr. Brian Beal oversees shellfish production and research at DEI; he's a professor at nearby University of Maine at Machias, and he's been working with shellfish for a few decades now. He and his staff, Hatchery Manager George Protopopescu and assistant Kyle Pepperman have been trying to get their flat oysters through full production for a couple of years, and have had decidedly mixed success. In 2009, they had a good run, producing 100,000 juveniles, but since then have had little joy.

The main problem is in the larval phase; that roughly two-week period of time when the larvae have left the female, and are being fed and cared for by the hatchery. Worms and other animals that hitchhike on the shells of the adults end up spawning as well and their tiny offspring compete for food with the small oysters, or eat them, or just change the water quality to a poor state for oyster larvae. While the DEI staff have overcome a large part of this by the novel approach of spreading a marine adhesive over the shells (prevents the hitchhikers from spawning), they still have a bit of a problem to overcome.

Also, there seems to be a bacterium at play in the larval tanks, one that ends up killing small oysters such that they end up clumped up in a pile, dead. Brian, George and Kyle are experimenting with some prophylactic approaches for this, but I can tell you that she ain't solved yet.

So, when I stopped in to talk with George and Kyle on Monday last, George was realistic (not what you'd call giddy) about the chances for the upcoming spawn, while being optimistic about the effectiveness of their new procedures, and chances for success. If they are successful, then oysters will go out to cooperators in industry for nursery culture and growout. Since flat oysters like cooler, more moderate water temperatures than their Eastern cousins, and since we've got a lot of that kind of water around here in Maine, they are a reasonable species to culture, especially for the many fishermen in the state who are beginning to experiment with aquaculture.

Above: Dan Canfield, a shellfish grower out of Tenant's Harbor, Maine and a former commercial fisherman, has a few flat oysters on his farm, and hopes to begin going to market in 2011.

So, for now, my visit was a reinforcement of the promise and the problems with the flat oyster. A couple of years ago, I organized a session on O. edulis at the Northeast Aquaculture Conference and Expo (NACE) in Portland, and one of the titles in the session summed it up accurately. Dr. Andre Mallet, who hails from Shippagan, New Brunswick, and who is himself an accomplished scientist and shellfish producer, called the flat oyster the Beast of Sorrow. Sheesh. Nonetheless, given the allure of a steady supply of belons to the market, I'm sure that Brian and company will persist, and they are every bit as likely as anyone to succeed.

Aquaculture is not for the faint of heart.