WELLFLEET — Sometime in June, a fleet of pickup trucks rumbled into the Dunkin’ Donuts parking lot and met for a handoff. Their drivers were “not making a drug deal,” said “Johnny Clam” Mankevetch, Wellfleet’s assistant shellfish constable, in a talk at the 19th annual State of Wellfleet Harbor Conference last month. “They were waiting for quahog seed.”
His talk summarized what the town’s shellfish dept. has been learning from experiments that began back in 2018 to compare shellfish propagation strategies.
Complementing the department’s work, the nonprofit Wellfleet Shellfish Promotion and Tasting (SPAT) has funded a three-year study led by biologist Barbara Brennessel. Now in year two, her research is providing insights on how tidal restoration at the Herring River may affect oyster larvae settlement.
Obtaining quahog clam seed involves engaging with a “seller’s market.” For the shellfish dept., “there’s a lot of phone calls and phone messages and waiting,” Mankevetch said. And when it comes to the shipping date, hatcheries set the pace.
This year, the shellfish dept. bought 500,000 quahogs, each about four millimeters long. In June, the hatchery representative rolled into Wellfleet with half the load. The other half arrived in August.
The shellfish dept. piles the seed into mesh cages destined for Wellfleet Harbor — but not without first raking the bottom for predators. “If you have crabs under your quahog netting,” Mankevetch said, “they have nothing to do but eat.” From there, the clams mature in the tidal flats, and in three years or so they’re ready for harvest.
As the tide goes out, the receding water in Chipman’s Cove uncovers loads of “happy little clams,” Mankevetch said.
Wellfleet’s supply of happy clams comes not only from hatchery seed purchases but also from a quahog relay program based in the Taunton River — “a wonderful quahog growing area,” according to Mankevetch, “that’s mildly yet hopelessly contaminated with fecal coliform.”
These Taunton River clams are off-limits for harvest. “But when they’re put in clean water, the shellfish will continuously filter and flush out the bacteria,” said Brennessel, a Wellfleet-based biologist who has served on the town’s shellfish advisory board and conservation commission.
Wellfleet purchases these contaminated quahogs in June for around $20 per tote, and the shellfish are dispersed in the harbor. Within a few days, the clams pump out the coliform and can be state-certified for consumption — but Wellfleet keeps them undisturbed through their spawning period.
“This is important,” Brennessel said. “It’s not like you put them there, and as soon as they’re clean, you harvest them. They’re left there long enough that they can spawn and make more shellfish for Wellfleet Harbor.”
Harvesters can come after this spawning period ends sometime in September, and they’ve reported back this year with sightings of quahog seed. The appearance of wild seed floating in the waters is promising news, especially as littlenecks (small quahogs) have been enjoying a “historic price in the market,” Mankevetch said. “Our commercial fishermen are truly reaping the benefits of this program.”
A June Jackpot
Unlike clams, oyster larvae (also called “spat”) can cling to a substrate. When it’s spawning season, the shellfish dept. catches wild spat on plastic disks coated in lime-rich cement. Curving into wide-rimmed cone shapes, these apparatuses are called “Chinese hats,” and they sit in stacks along the harbor. Chipman’s Cove and the mouth of the Herring River are two prime spots.
The department also does “cultching,” another rendition of this spat-catching principle that involves laying down rows of empty shells in the intertidal zone, where larvae can grab hold.
Historically, shellfishermen have followed a rule of thumb: those Chinese hats should hit the water near the Fourth of July. Two years ago, however, that schedule returned a meager catch. But the few who happened to deploy their devices in mid-June landed a jackpot, so, this year, spat collection kicked off by the second week of June, and the hats “caught magnificently,” Mankevetch remarked. “You could hardly lift them off the bottom and put them onto the truck.”
When they first stick onto the hats, young oysters have grown only one shell. By the end of September, the back shell forms, and soon after they’re ready for mesh growing bags. In theory, to do this “you just flex the disk, and they pop off,” Mankevetch said. “It doesn’t really work that way all the time. There’s a lot of banging involved.”
From there, the oysters return to the tidal flats, where they’re grown in bags until they hit market size — or until January, when the threat of harbor icing looms. Ice can churn up equipment and devastate an oyster grant. “We all live in abject fear of ice,” Mankevetch said. “If you leave your racks and bags out in the ice, it creates an outrageous, unfathomable mess of twisted rebar.”
At this point, hundreds of thousands of oysters take refuge at the dump — that is, they’re hustled out of the winter waters and thrown into an oyster pit under the auspices of the town transfer station. In early March, “you take them out and they sound dry and rattly,” Mankevetch said. “You go, ‘Oh, no — these are all gonna be dead.”
But once the oysters return to the water, “they refresh,” he continued. “They’re alive, the great majority of them. I’ll never stop being amazed at that.”
With the Herring River Restoration Project in the near future, shellfishermen have been wondering how tidal restoration in the river’s basin may change where spat settles in Wellfleet Harbor.
“I realized that no one had studied it,” Brennessel told the Independent. “It wasn’t scheduled to be part of all the other studies that were done as part of the restoration,” she said, adding, “It seemed to me like a simple enough thing to get some baseline data before the restoration.”
Working through the Friends of Herring River, she proposed the idea to SPAT — the nonprofit that organizes Wellfleet’s OysterFest and supports research and education on the ecology and economy of shellfishing and aquaculture here — and received a grant to pursue it.
Aided by retired National Seashore ecologist John Portnoy and Silas Watkins, who was still a student at UMass Amherst in the project’s first year (he has since graduated), Brennessel wrapped up the second year of her Herring River estuary spat settlement study in September.
The team collected spat from four sites along the estuary. For comparison, they also monitored settlement at Jake and Irving Puffer’s Mayo Beach grant, which reliably catches wild oyster set.
This year, they found that spat could settle on the site just landward of the Herring River dike. But at a spot National Seashore scientists call the Dog Leg, the last place where salt water reaches upstream and which experiences far less tidal flushing, they found none.
“I hypothesize that, with restoration, there’ll be increased settlement further upriver,” Brennessel said. “And that the conditions will be more favorable for the growth of oysters above the dike.”