Pismo Beach was once the Clam Capital of the World.
Then the clams disappeared

PISMO BEACH, Calif. — Pismo Beach loved its clams.

More than a century ago, farmers with horse-drawn plows would comb the sand and haul the clams off by the wagon-full. The meat was fed to the hogs. Softball-size bivalves were so abundant, they could be found rolling ashore by the dozen at high tide.

Californians of a certain age may remember visiting this Central Coast town and renting specialized “clam forks” to dig up the tasty mollusks. Even Bugs Bunny visited, declaring in a 1957 cartoon that he and Daffy Duck had “all the clams we can eat.”

Pismo Beach was indeed the Clam Capital of the World. But did it love them too much?

At the Pismo Beach Clam Festival last month, the entries in the chowder contest did not include the native species. Local clams haven’t been tossed into chowder here since 1947, around the time the commercial clam fishery closed.

Still, recreational clammers reportedly dug up the shellfish by the millions through the 1950s, and by the thousands through the 1970s. But the last time someone found a clam large enough to legally keep was in 1993.

Though the clams survived elsewhere, in Pismo Beach they had all but disappeared. During “clam digs” staged for children at recent festivals, kids unearthed plastic shells buried by the organizers because the real ones were too precious to disturb.

Which is why scientists are trying to answer a perplexing question: What happened to the Pismo clam?

Efforts to unravel the mystery of the disappearing clams go back years. On a fall morning in 2018, researcher Alex Marquardt held up a purplish striped shell in the palm of her hand. Compared to clams a generation ago, this one is minuscule.

“They’re the cutest things I’ve ever seen,” she gushed. “A quarter-inch and practically perfect in every way — they’re Mary Poppins clams.”

Then a graduate student at Cal Poly San Luis Obispo, Marquardt was leading the effort to help explain the clams’ decline and perhaps find ways to restore them across their natural range from Monterey to Baja California.

Marquardt and a team of undergraduates and volunteers had spent the three previous summers surveying beaches up and down the coast as part of the Cal Poly Marine Conservation Lab’s Pismo Clam Project. A mollusk enthusiast through and through, she has a Pismo clam tattooed on her left arm to go along with some phytoplankton ink from a previous job.

To conduct a monthly clam census, the crew hit the beach with shovels, wagons and plastic buckets. The work commences when the tide is at its lowest. In the summertime, that means digging in the middle of the night.

Divided into three groups, they dug trenches, dumping shovelfuls of sand in their wagons lined with one-inch chicken wire. Water was poured over the sand, and the makeshift sieves-on-wheels revealed sand-burrowing creatures.

It didn’t take long for the gulls to start circling.

“The birds are going after them too, so they’re here,” Marquardt said.

Soon, a California Department of Fish and Wildlife truck rolled up. Chris Foster, a game warden, hopped out to chat and noted clam poaching remains a problem.

“The bad guys,” he said, “know right where to find them.”

Until the early 1980s, Pismo clams seemed to be reasonably abundant. But then something went wrong.

The population’s decline, depending on whom you ask, coincided with the return of a voracious predator to the Central Coast, the sea otter. The mammals were nearly hunted to extinction on the West Coast during the fur trade in the 18th and 19th centuries. As federal protections helped the otters rebound, Pismo Beach noticed their big clams started to disappear.

But the explanation can’t be that simple, said Ben Ruttenberg, who runs the Marine Conservation Lab at Cal Poly San Luis Obispo. Clams and otters lived in balance with each other for thousands of years.

Humans, too, have a long history with the shellfish.

The Chumash people harvested clams, piling Pismo shells in middens along the coast. Both city and shellfish get their names from the Chumash word for tar, pismu. In some ways, both the city’s and clam’s identities are hinged together.

During the Great Depression, Pismo Beach businesses used clamshells as scrip. The larger the shell, the larger the value. One shell, six inches wide with deep purple stripes and now on display at City Hall, was worth $20 at F.W. Wolverton in 1933. Today, that’s more than $400.

To this day, Pismo Beach celebrates the clam, even in its absence.

Artists paint and decorate giant concrete clam statues located around town for different holidays. Utility boxes near downtown feature clam-themed art. Gift shops sell postcards featuring 1950s clammers, yearning for “the good old days.”

The Pismo’s scientific name is Tivela stultorum. “Tivela” is the genus of saltwater clams. “Stultorum,” in Latin, means lazy.

It’s a fitting name. A study from 1995 found Pismos are among the slowest-digging bivalves, the fastest are the sleeker Pacific razor clams.

To move, the oblong Pismo extends a slimy “foot” from its shell to dig itself into the wet sand in a series of plodding motions. Their shape and heavy shell makes it easier for them to anchor themselves in the sand, but harder to move around once buried.

Pismo clams and humans seem to like Pismo Beach for many of the same reasons. Here, the headlands of Port San Luis protect the beach from intense waves. The sand is also fine without too many rocks.

Scientists are unsure how long it takes a clam to reach legal size; estimates range from 10 to 14 years to grow to 4.5 inches. That’s the size set by the state to legally harvest them if you’re south of the Monterey-San Luis Obispo county line and have a state fishing license. Undersized clams must be reburied with their “button” facing up and hinge toward the ocean.

In some places in Southern California, legal-sized clams can still be found, but researchers are hesitant to say exactly where for fear of attracting poachers.

Cal Poly scientists have been investigating the disappearance of the clam at Pismo Beach since 2013, when the City Council provided funding for preliminary surveys.

Around 2016, came somewhat encouraging news. The researchers observed “pulses” — a proliferation of small, young clams on the beach.

This phenomenon, called broadcast spawning, is common in other marine species, including many fish such as tunas, sea urchins and abalone: Young animals all sort of show up at once. Most eggs and larvae get eaten by predators, but sometimes huge numbers beat the odds and survive, leading to mini population booms.

Did these pulses signal a rebound for the beloved species? Or would the same factors that nearly wiped out the Pismo clam strike again?

On that fall day in 2018, Marquardt and her crew continued their census. “Where are you, clams?” Marquardt asked.

After almost an hour of work, the teams had excavated several 100-foot-long trenches. Some scooped sand on to the wagons topped with chicken wire while others dumped buckets of water to melt away the sand. The reveal: a surprising diaspora of ocean life — sand crabs, sea snails, polychaete worms and some things that even Ruttenberg, the marine ecologist, couldn’t identify.

Finally, the teams started to strike gold just a few inches deep: dozens of the banded brown shells of the Pismo clam.

When a group of beachgoers wanted to know what was going on, Marquardt stopped digging to explain. “We are doing research on Pismo clams.”

One kid inspected the contents of a wagon. “Oh, that’s a pretty big one!”

“No, these guys are little,” Marquardt said.

The biggest they’d ever found on Pismo Beach was about 3 inches.

Just as one conversation ended, another seemed to begin with passersby young and old. Such is the magnetism of the Pismo clam.

“Are they clamming? I thought clamming was done earlier in the morning.”

“We are not clamming,” Marquardt said. “We’re doing research on clams.”

When Marquardt spotted a clam, the conversations stopped. “Hey, look at that! Ta-daaa!” she said as she plucked a small brown bivalve from the wagon. This was a bean clam, which can resemble a young Pismo in size and color patterns.

Most Pismos are sort of beige with darker brown or purplish bands that generally correspond with age, like the rings of a tree trunk.

Some shells have long purple stripes radiating from hinge to opening. Marquardt calls these “stripey ones.” The “old literature” from almost 100 years ago, which contains some early descriptions of clam biology, estimates about 5% to 10% percent of the population have these features. Why? She shrugged.

Because the clams reproduce by spawning, there’s no sexual selection — no clam mating dances — and thus no apparent evolutionary reason for the coloration. Another mystery on the list. Marquardt resumed digging.

Her shovel stopped short. Through the handle, she felt a clamshell.

“I’m glad that I felt that one because the first couple surveys...” Marquardt started to tell a story but stopped to answer another question and marvel at three more clams. “Oh it’s a wee babe. It’s so cute!”

Back to digging.

“I can feel them through the shovel,” she continued. “It’s like a weird superpower.”

For Pismo clams, threats abound, and not just from humans. Ruttenberg inspected a clamshell with a small hole bored through it. He suspected that a sea snail called a whelk drilled the hole and ate the clam from the inside out.

Pismos “make a whole bunch of babies,” he said. “Most of them die. They have to run through a whole bunch of gantlets just to become an adult clam.”

It’s been three years since Marquardt conducted her surveys, and she’s moved on to other work. Last month, the Pismo Beach Clam Festival returned after a coronavirus-induced hiatus in 2020. Costumed mascots Sam and Pam the Clam once again marched in the parade as the grand marshals.

Standing behind a table covered with photos, literature and an old clamming fork, Peggy Coon held up a worn cream-colored shell — a legal-sized clam plucked from the sand long ago. Coon is a volunteer docent for the state park and she had news for a captivated young family.

“Have you heard the clams are starting to come back?” she asked.

It’s true. No one has seen these many clams on the beach for years.

In July, Cal Poly researchers counted and measured 35,000 clams in three days of surveying. That’s more than what they found in the previous five years of research.

“You can’t even walk on Pismo Beach right now without stepping on clams,” said Cal Poly graduate student Marissa Bills, who now leads the clam research project.

Most of the clams, researchers say, are still about 3 inches long, many years from reaching a size legal enough to keep. That hasn’t stopped some beachgoers from — intentionally or not — illegally taking them.

That’s why over the summer, the California State Parks department tasked its volunteer docents with walking the beach at low tide and high-visitation days. The goal: Teach visitors to leave the clams alone.

Coon began volunteering at the Pismo State Beach Monarch Butterfly Grove 14 years ago. Now once a week, she roves the beach with a bucket that reads “Learn how to save and bury a Pismo clam.” She keeps an eye open for people taking clams or kids using them as sand castle decorations.

“People are poaching them because they remember the good old days” she said. “But the good old days aren’t back yet.”

Illegal harvesting still presents a threat to the clams’ long-term recovery. Game wardens watch for people doing the “clam shuffle.” They make a back-and-forth movement reminiscent of doing the Twist, but they’re really feeling for the rough texture of clamshells.

In 2020, despite closures to some areas of the state park to vehicular traffic, Department of Fish and Wildlife game wardens seized a record of 25,000 undersized clams and issued 225 citations.

Sometimes, people will use kids’ sand buckets to collect the shellfish, said Lt. Matt Gil, the game warden who supervises Monterey and San Luis Obispo counties.

Officers have caught people cooking the clams right on the beach. In one case, a group of people had stuffed an umbrella bag full of 368 clams.

Illegal clamming comes with a hefty price for the offender: a misdemeanor violation is more than $1,000 — plus a base fine of $20 per mollusk over the limit of 10. In the Pismo Beach area, an average of 68 clams are seized per citation.

To help keep tabs on the clams, the Cal Poly researchers in August bedazzled dozens of shellfish with QR codes and reburied them, logging their locations down to the centimeter. Now when they find a tagged clam, they can compare its previous size and location.

And the public can help, too. When scanned, the QR code links to a survey asking for a photo of the clam, its location, whether it’s alive or dead and if it was found above or beneath the sand. The data will allow the scientists to calculate the clams’ growth rate with greater accuracy than counting rings on the shell. They’ll also have a better understanding of mortality rates.

To the researchers’ delight, the team found eight clams exactly where they buried them upon re-surveying the area in October. So far, 30 beachgoers have found tagged clams and filled out the survey.

What remains unclear is where all these clams are coming from. Are they spawning locally, or are free-floating larvae drifting in from Morro Bay or Santa Barbara? It’s also unclear what’s preventing the clams here from reaching legal size. Some of it is poaching, Ruttenberg said, but predation and changing ocean conditions also play a part in this story.

Still, new pulses of Pismos continue to appear on the beach. The researchers are seeing bigger clams, smaller clams and many in-betweens, all living and growing in the sand at the same time. A sign of a healthy population.

As Ruttenberg and Bills work to understand the many mysteries of the wild population, they’re also trying to develop techniques to spawn and grow Pismos in the lab.

If successful, the effort could revive the commercial harvest of Pismo clams through aquaculture. Then perhaps Pismo Beach restaurants could use local clams in their chowder, just as locals did decades ago.