How Oysters Are Grown: A Visit to Island Creek Oysters in Duxbury, Massachusetts

Grower Tour

Pin it button big

WhoIsland Creek Oysters
Where: Duxbury, Massachusetts

One hot sunny day last week, I drove to Duxbury, Massachusetts to find out how oysters grow. My destination was the Island Creek Oyster farm, an oyster farm set in the cold, salty water of Duxbury Bay, about 30 minutes southeast of Boston. For years I've slurped oysters from their shell with little knowledge of how these bivalves came to be, but that was all about to change. 

Pin it button big

The History of Island Creek Oysters

Island Creek Oysters' founder and lifelong Duxbury resident Skip Bennett started farming oysters here in Duxbury Bay in 1995. Since he was the first person to try growing oysters in this part of the country, it took about six years before he had his first big crop. "Skip likes to say he killed a lot of oysters in the process of figuring out how to make them live," says Chris Sherman, Vice President of Island Creek Oysters, and my guide and oyster guru for the day. Back then Skip sold around a 100 bags a week (each bag held 100 oysters). Now Island Creek Oysters sells 120,000 oysters a week, and services 350 chef accounts around the country. 

So how does one grow oysters? What's the process? What makes a good oyster? At Island Creek, it all starts in the hatchery.

Pin it button big

Chris Sherman, VP of Island Creek Oysters and my guide and guru for the day.

Hatching Baby Oysters

The life of an Island Creek Oyster starts in the early spring in the Hatchery, which sits in a warehouse on the shores of the bay. While most oyster farms buy generalist seed that's good for their region, Island Creek grows oysters specifically bred (by them) to flourish in the waters of Duxbury Bay. In fact, they're one of only about 12 oyster hatcheries in the country. 

The air in the warehouse is hot and moist — perfect conditions for spawning. Oysters can't spawn in Duxbury Bay because it's too cold, Chris tells me. So at the start of the season, in the spring, the farm crew collects a few "really handsome devils" to bring back to the hatchery to spawn — the first of 7 or 8 spawns they'll do throughout the season. "Just like you would a horse or dog, you get the ones that have the traits that you're looking for," says Chris. "What we're selecting for is shell depth, meat content, growth rate, disease resistance." Once they've collected the oysters they want to breed, the crew dumps them in large blue tanks full of warm water so they get ripe and build up gamete. ("Turn the lights down, put a little Marvin Gaye on" says Chris, with a wink.) When the oysters are rarin' to go, the crew moves them to a spawning tray where the oysters spew their gamete out into the water — 75 million "free swimming larvae" that will need to some help to become oysters!

From there the larvae move to one of six large tanks for a time, and when they're the size of a dust particle, the process really starts to get interesting: the oysters are ready to "set" and begin building their shell. To do this, they need the teensiest bit of calcium carbonate to wrap themselves in. (For more on this process, see Fact #3 below!) The old fashioned way to provide calcium carbonate to farmed oysters was to grind up old oyster shells into a fine micron powder, which you'd sprinkle into the puddle of larvae. But the way Island Creek Oysters does it now is to pour the larvae into a calcium carbonate bowl with a super fine 130 micron screen. Then the bowls are placed in a "downwelling system" — basically a trough underneath a constant flood of water and algae — for 4-5 weeks, where they grow from "looking like dust to looking like a flake of ground pepper," says Chris.

"Oysters go through a metamorphosis, like a butterfly," says Chris. "But it's kind of the opposite — it's kind of a 'bummer metamorphosis.' They go from being a sweet larvae that gets to cruise around wherever it wants to an oyster that has a shell and sits in one place. So, it's kind of a buzzkill for them." 

Pin it button big

Growing Baby Oysters in the Upwellers

Water flow — the constant movement of algae (food for oysters) and calcium bicarbonate (for their shell) — is what helps oysters grow. So at about five weeks, the baby oysters get moved from the hatchery to the upwellers — a sectioned off area of screen-bottomed boxes in the bay underneath the dock. Each box connects to a central trough which continually pumps water and nutrients to the baby oysters. With the upwellers, "again it's all about water flow," says Chris. "It's one of the major things to do as an oyster farmer, to shuffle volume around."

Oysters grow rapidly in the upwellers, doubling their volume in the course of a day. Here's how the upwellers work, according to Chris: "You take a little wet nap which weighs around two pounds and has 800,000 oysters in it, you put it in one of those boxes [and set it on the screen], you come back 18 months later and that same little two pound wet nap will weigh 280,000 pounds and they take up an acre of the bay." When the oysters are about the size of the nail on your pinky finger (about 1/4 inch) they're ready to move out into the river.

Pin it button big

Bulking Up in the Nursery

The water in Duxbury Bay is very cold and very salty. It's almost full ocean salinity, which is really rare for a little estuary. But "the colder the better for oysters," says Chris. "[This water temperature] is really good for growing meat, which is what we want... The goal with growing oysters is to get them as big as possible before the winter so they can survive."

After the baby oysters make their first big growth push in the upwellers, the crew packs them into large black mesh bags (about 1200 baby oysters in each bag) and moves them out into the river near the bay, where they'll stay for about 6-8 weeks. After that they move to the nursery, a system of cages that sit, in rows, on the bottom of the bay. They'll live here for 2-3 months, or until they're about 2 inches long.

Pin it button big

Mud Planting and Harvesting 

"The planting process is the most ritualistic part of oyster farming," Chris tells me. After the oysters reach a certain size in the nursery, the crew takes them out of the black bags and scatters them free range on the bottom of the bay. Oysters will continue to grow in the mud for another 1.5 to 2 years before the crew harvests them.

The ideal oyster has a nice round shape and a deep cup, but sometimes they don't grow that way. If an oyster isn't big enough, or has a crazy shape, the crew will throw it back into the water to self-correct. "The cool thing about oyster farming is that it's not like harvesting corn where you just harvest everything and the stuff that doesn't make the grade gets chucked. We put it back in the water... it fixes itself, and we harvest it again," says Chris.

The crew harvests oysters by dragging a metal rake along the bottom of the bay, which pulls in hundreds of oysters every few feet. (Because the muddy bay bottom is otherwise barren, there's no need to worry about bycatch.) They then deposit the oysters into orange buckets — 200 oysters per bucket — and take them over to the Oyster Plex, a floating dock in the middle of the bay, to process. Here the oysters get culled by size: the selects (the 2.5 inch oysters with a nice, round shape), which mostly get sent to restaurants in New York; the jumbo oysters, and the 3 inch oysters.

Pin it button big

As with any kind of farming, it's a tricky business, and very dependent on factors that are often out of your control, so a diverse mix of oyster lines and breeds is essential: "The weird thing about oyster farming," Chris says, "is that we do so much bet hedging because it's so unscientific and there's so many variables that come in. Something in the water is significantly more sensitive to its surroundings than if you're growing corn: there are 37 different variables in the water, from temperature to salinity, pH, dissolved oxygen, turbidity that gets affected by the natural conditions, so it's very hard to predict."

Still curious about oysters? Here are a few other surprising things I learned:

6 Facts You May Not Know About Oysters

1. Oysters are sequential hermaphrodites.
This means that at some points in their life they're male, at other points they're female, and they switch back and forth. "We don't know what we have until we spawn," says Chris. 

2. Newly spawned oysters only need the teensiest (as in, almost microscopic) bit of calcium carbonate to start growing their shell.
Oyster larvae essentially "wrap" themselves around their few little individual molecules of calcium carbonate to get the shell started. They then add to their shell by filtering calcium out of the water. 

3. In the wild, oysters set on (or attach to) old oyster shells. 
When oysters grow in the wild in oyster reefs, they typically attach to old oyster shells (for the calcium carbonate — see above). Because of this they tend to grow in clusters and one on top of the other. This is also why wild oysters typically have "gnarly shapes," says Chris, instead of the nice round shape and deep cup you associate with farmed oysters.

4. An oyster can live for about 30 years, and the lighter the oyster, the younger it is.
A really light oyster means that's very young, as oysters get heavier as they get older. "They start adding shell and adding meat. They don't get longer necessarily, but they bulk up," says Chris. Island Creek even sells jumbo oysters that measure around six inches and weighs a pound. They're safe to eat, just maybe not the best tasting. "It's really not much different; it's just weird to have to take a steak knife to your oyster."

5. The best time to eat oysters is in September or October.
Like all New England seafood, oysters vary quite a bit in flavor seasonally. The "selects" — the 2.5 inch oysters with a nice round shape and deep cup — will bulk up by the fall and then they'll be perfect, "really plump and sweet" according to Chris. By September or October, oysters are through the hot months and the time they're thinking about spawning, and they're more focused on gearing up for winter. "So like a bear puts on fat, [oysters] do the same thing... [which means] most seafood is ready to eat in October. Everything is ready to rock for winter, and they're at their prime."

6. Oyster farming is a lot like making wine.
"We draw a lot of parallels between oysters and wine," says Chris. "Being out [in the oyster flats] you can really see — it looks like a vineyard! All these rows are positioned to maximize the exposure to the tidal flow that comes up into the bay everyday." Oyster farmers call it the merroir. "When you eat an Island Bay oyster, you smell Duxbury Bay," says Chris. "You smell what we're smelling right now, and that's a big part of what makes an oyster good or not so good."

Thanks, Island Creek Oysters!

(Images: Cambria Bold)