Growing and Harvesting Oysters

article image

Nature’s perfect food — and eco-friendly, too!

Over the years, people have often asked me about the nutritional content of oysters. I always think of them as a delicious food that brings you in contact with the sea, but the oyster is also one of Mother Nature’s most perfect foods. In fact, it’s so packed with nutrients, it’s no wonder most people experience a protein-induced buzz after eating a number of oysters.

  • Oyster are high in omega-3 fatty acids and low in cholesterol. They’re an excellent source of vitamins A, B1, B2, B3, C, and D, and are loaded with minerals such as iron, magnesium, calcium, selenium, and zinc. They’re also a good source of easily digested protein. A 100-gram serving of raw C. gigas oyster meat contains 73 calories and just 2 grams of fat; 100-gram serving of C. virginica contains 60 calories and 1.5 grams of fat — perfect for health-conscious diners who are watching their figures.
  • Oyster farmers don’t feed or add any chemicals to their crop. Instead, they keep the oysters in an area where they can grow and be fed by Mother Nature.
  • Oyster farming, or aquaculture, is a sustainable resource that helps keep the environment healthy. As oysters snack on plankton, they help keep its growth in check. An overabundance of plankton clouds the water’s surface and prevents nourishing sunlight from reaching the aquatic wildlife below. (Just think of oysters as envi­ronmental heroes!)
  • Far less energy input is required to produce an ounce of protein from an oyster than most any other protein source. Beans to beef, oyster (and cultured filter-feeding shellfish) trumps all. No feed, antibiotics, water, energy/electricity needed to grow, and little fuel is required to harvest (depending on how far from land the oyster is grown). Save the ocean (ahem, the world), eat an oyster!

At the bar, I try not to say that oysters are a healthy food, good for you as well as the environment — as that type of image ruins the oyster’s sexy, late-night aphrodisiac qualities — a real shuckin’ PR nightmare.

To Grow an Oyster

Edible oysters grow naturally near the coast or on banks farther off shore where the water temperature is right and the sea bottom firm. They do particularly well in estuaries, where seawater mixed with sweet water nourishes the growth of the types of plankton that suit them.

Our ancestors originally gathered oysters by picking them up full-grown on the shore at low tide or by lifting them from natural beds at sea. In Europe, the coarse, cheap oysters of the mid-nineteenth century were a product of that kind of fishing, but they were fished out. A natural supply of mature oysters is rare in Europe nowadays.

In countries such as England, Ireland, and France, oyster cultivation consists of two stages: obtaining young oysters, and tending them as they grow and fatten.

According to Neild’s The English, The French, and The Oyster, there are two traditional methods of obtaining young oysters: by dredging a natural bed for spat and part-grown oysters; and by collecting on a private bed any spat that formed when larvae drifted in from natural beds or from private beds nearby. Once young oysters are 1/2 inch or more in size, they are known as brood and are bought and sold for laying down to grow and fatten.

The key to the breeding of oysters, whether on public or private beds, is to have enough breeding stock in a suitable place and to maximize the area of sheltered clean, hard surfaces on which larvae can settle to form spat. The traditional method of doing this is to provide a hard bed of “cultch” — a mixture of the old shells of oysters, cockles, mussels, and other shellfish, plus other suitable oddments, such as bits of broken crockery, and ceramic roofing tiles. In the middle of the nineteenth century, manufactured surfaces, or “collectors,” were intro­duced in France (a Roman practice rediscovered).

Before the spatting season, the bed needs to be raked to remove weeds and to lift existing cultch out of the mud, and new cultch needs to be added. Artificial collectors have to be prepared and put out.

The oyster grower needs to watch over the oysters regularly to make sure they are not smothered by silt, sand, or weed; damaged by predators, pests, or competitors for space and nutrients; or stolen.

Oyster laying, both for breeding and for later growth, may be on the foreshore (the area between high and low tide), or farther out to sea. With a laying on the shore, the oyster farmer needs to ensure that the oysters are covered in seawater all or most of the time while still enabling himself to tend them on foot.

Where the shore is relatively flat, an oyster grower can enclose an area above the normal low-tide level so that it will retain a few inches of water while the tide is out. Such enclosures are called parcs in France.

Oyster beds farther out have to be tended from a boat with dredges and harrows. The aim of dredging is to skim off oysters, cultch, and rubbish. What is brought up is sorted. Rubbish will be removed and oysters thrown back until they are ready to be harvested as brood or for consumption.

Before oysters are marketed, they may be moved into areas where con­ditions are ideal for fattening them and for maximizing their flavor. In some parts of France, a complex system of artificial beds, called claires, has long been in use for this purpose. Claires are shallow basins with clay walls located in marshy areas at the level of high tide. Water is let into them at high spring tides and retained by a system of dykes and sluices until the next spring tide. In the summer, the stagnant water in the claires develops a bloom of blue-green organisms that tinges the oysters a greenish color — an indicator to the consumer that these are among the most flavorful of bivalves. Claires were first introduced at Marennes, which at one time was a major source of flat oysters and was renowned for its seasonal supply of Marennes vertes.

Oysters in the Bag

Amédée Savoie and Maurice Daigle, the owners of La Maison BeauSoleil in New Brunswick, on the East Coast of Canada, place their oysters in mesh Vexar bags suspended from long lines until mature, without being finished on the bottom — an interesting varia­tion on a practice that dates back to Roman times. This labor-intensive approach produces a consistent Cocktail oyster with a meat-to-shell ratio greater than any other oyster on the market. It’s always full and plump, with a lovely salty-sweet taste and steely, clean finish.

Wild in Galway

Galway oysters are one of the few true wild oysters that I know of. Apparently, local folks tried to aquaculture the O. edulis, with limited success. So they returned to their original methods of stewardship. When the beds start getting thin, they’re closed to harvesting for up to five years so the oysters can grow and replenish the stock. When the beds reopen, the oldest oyster can weigh more than 200 grams. If you happen to know the grower personally, some of these gems might just end up in your order (thanks Dairmuid and Michael!).

Michael Kelly, of Kelly Shellfish, has a grow-out lease of 800 acres in Inner Galway Bay, which is fed from the fresh runoff of the fields of Athenry and flushed by cold Atlantic waters. This magical combina­tion creates one of the world’s most distinctive oysters, available only from September to April. The oysters are finished over 10 acres in Killeenaran, Clarenbridge. “The Fields of Athenry” is a well-known song everyone sings with tear in their eyes while dancing on chairs at the Oyster Festival. It’s a Galwegian thing.

The family has six full-time and six seasonal employees who together harvest some 200,000 oysters a year. Mature oysters are dredged out of the Inner Bay and rest in the finishing area for a number of days or weeks. To harvest them, the Kellys simply walk out at low tide and gently lift the oysters into a waiting basket with the help of a stiff rake or pitchfork. The harvested oysters are taken back to the farm for cleaning, culling, and grading. They’re then loosely arranged in trays of 100 and returned to the water to rest again. “The oyster doesn’t like to be brought out, then boxed and shipped,” Mr. Kelly Sr. told me one year. “Too much shock to their system. Better to let them rest for a couple of days, then they’ll travel better.”

Oystering À La Carte

Foraging for your own seafood by the sea is an unforgettable expe­rience. It’s also easy, if you know what you’re doing and you do your homework in advance.

No matter where you go, even if you have land with a water view, call the local Fisheries office to make sure the area you are harvesting in is in good condition. They’ll be able to tell you what shellfish is available in that area and what the limits are.

You’ll need a pair of rubber boots, a bucket, an oyster knife, and some gloves. Oyster shells can be sharp, especially in warm weather. The boots will keep you from cutting your feet, which is not fun.

Head to the area at low tide and pick up oysters as you walk along the beach. Quite often, you’ll find a group attached to rocks or other objects. Just take the knife, pry a few off, and put them in the bucket. Make sure you test a few, of course, to ensure they taste good.

When your bucket is full, take your oysters home and rinse them under cold water. If they are muddy, a little scrub brush will help.

You can serve the oysters at “ocean” temperature, as you found them, which provides the best flavor. To chill them before shucking, make a bath of ice and water and let the oysters sit in it for 20 minutes.

After your feast, return the shells to the area in which you found them to give spat a good place to set.

More from The Oyster Companion:


The Oyster Companion excerpted with permission from Firefly Books. Published by Firefly Books Ltd. 2018 / Text © 2018 Patrick McMurray.

Real Food

Cooking fish and other seafood at home is much easier than you think! Fresh Fish offers simple step-by-step instructions for all of the essential cooking methods, including baking, pan-frying, braising, broiling, steaming, poaching, roasting, marinating, and grilling — along with 175 mouthwatering recipes that bring out the best in everything from fish fillets and whole fish to shrimp, mussels, lobster, clams, calamari, and more. You’ll also learn how to buy fish (even whole fish) with confidence, how to serve fish raw, how to clean freshly dug clams, and much more. Order from the MOTHER EARTH NEWS Store or by calling 800-234-3368.