How Exactly Do You Farm Oysters?

Mar 28 at 11am

By Calin Van Paris

When the sun is high in the Bay, there are few snacks more enjoyable than a platter of chilled, raw oysters paired with a crisp beer; they’re light, refreshing and they help get a pretty good buzz going. And whether you choose to venture across the bridge to their home in Tomales Bay, dine at the Napa Valley location, or head to the Ferry Building outpost, Hog Island Oyster Co. is a favored destination for those looking to sample the best-loved bivalve. But did you know that oysters are actually grown and farmed? Because I didn’t. Luckily, Lucas Sawyer of Hog Island was willing to explain the process to me.

To begin with, Hog Island Oyster Co. is a production beast. “We have over a million oysters growing right now,” says Sawyer, a member of the company’s seed crew. “Our goal is about four million per year, and you have to take the seed mortality rate, which is about 50%, into account. There’s a lot of survival of the fittest stuff going on.” The farm raises four types of oyster, including Atlantic, Pacific, and Kumamoto, as well as small batch varieties like the Belon. Hog Island is working with conservation organizations to re-establish the native oyster, the Olympia, in Tomales Bay. But I’m getting ahead of myself. Let’s start at the beginning.

New oysters begin as larvae spawned from full-growns. Most oysters are broadcast spawners, meaning they release their sperm and egg into open water and hope for the best. Pacific oysters spawn when water temperatures are high, whereas Olympia and Belon oysters are a bit more finicky about their potential offspring, making their spawning period a bit less predictable.

Our goal is about four million per year, and you have to take the seed mortality rate, which is about 50%, into account. There’s a lot of survival of the fittest stuff going on.

Larvae is collected and grown into seedom in a hatchery. Hog Island doesn’t currently have a hatchery to call its own, and instead receives shipments of seed from Washington and Hawaii. While at the hatchery, larvae is “set,” or placed in a heated seawater tank that allows each future shooter to attach to a surface, usually a perforated strip of plastic. The larvae are fed different types of algae as they mature and begin to develop a shell. 

The next stage of oyster life is the seed stage, and this is where their time at Hog Island’s West Marin farm begins. Seed varies in size, but is always small to begin with; the last shipment Hog Island received was made up of tiny dudes measuring about 1.5 mm. Seed this size is floated out to Hog Island’s Tomales Bay nursery in a series of Stanways. Stanways are mesh, cylindrical bags that, once filled with seed, are hooked into a water-immersed rack that rocks with the tide; the constant movement creates the round shape and “full cup” that mark an ideal Hog Island Sweetwater.

Oyster seeds

If the seed is too small for the nursery, it goes to the FLUPSY for further growth. The FLUPSY, a type of floating upwelling system, is a barge with a central trough that runs down the middle, to which bins are hooked, and a pump at one end. Water is sucked up through the bottom of the bins — made of different sizes of screen — through the oysters, into the trough, and out the pump, providing the filter feeders with necessary nutrients. As Sawyer puts it, “More food, more food!” 

After a time, young oysters (1/4 inch to 3/4 inch) are transferred to a new home.

The ‘French’ rack and back system is Hog Island’s preferred method, and one they’ve helped popularize throughout the region. Here oysters continue to grow in mesh bags elevated from the bay floor. A final method of oyster growth involves bottom bags, which are clipped to rope lines that lay in the mud flat.

 X-small Pacifics can be anywhere from nine months to a year old by the time they’re ready to eat, while mediums are around three years old by the time they're on your plate. Kumamotos and Atlantics take two and a half to three years before they're market size. 

As the oysters develop, feeding naturally on nutrients and phytoplankton, it’s the farm crew’s job to monitor their the growth, size, and shape  — and to keep them moving. Oyster racks are tipped up and hit with a baseball bat to break up new shell growth, which makes the oysters grow deeper bottom cups and stronger shells and also improves the firmness of the oyster meat. Think of this as P90x for oysters. Bottom bags are flipped with hay hooks to prevent the shell from growing into the bags.

“Everything is dependent on tide, and everything takes time,” says Sawyer. X-small Pacifics can be anywhere from nine months to a year old by the time they’re ready to eat, while mediums are around three years old by the time they're on your plate. Kumamotos and Atlantics take two and a half to three years before they're market size. So Next time you’re enjoying a Hog Island oyster, savor that little guy — he’s likely been readying for this moment for a few years.

Be sure to check out Hog Island’s Ferry Building location, which is slated to reopen as a full scale restaurant, complete with double the seating and a full bar, in mid- to late April.

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