YAMADA, Iwate Prefecture—A European oyster species that “disappeared” from waters around the Tohoku region after the 2011 tsunami was, in fact, just laying low.

Aquaculture farmers here are now helping the elusive bivalves continue their comeback.

If things go well, the European delicacy can be served when the Pacific oyster, the variety predominantly grown in Japan, is in short supply, according to a restaurant industry official.

On Nov. 6, the first cultivation process began for about 20,000 6-month-old European flat oysters in Yamada Bay off this town, home to a thriving oyster aquaculture.

By Nov. 11, 16 farmers were raising 70,000 of the species together. They hope to ship the product in winter next year.

“I was stunned to learn that the variety has survived in the bay,” said Hiroshi Yamazaki, a 34-year-old farmer who participated in the pilot program. “I will do my best to raise them.”

The European flat oyster is said to have brought to Japan from the Netherlands in 1952 by Takeo Imai, professor emeritus of oyster aquaculture at Tohoku University in Sendai. His goal was to raise the shellfish.

The town of Onagawa, also in Miyagi Prefecture, became the first site to cultivate the oyster variety.

By around 2000, oyster farmers at 29 sites in Hokkaido and the prefectures of Iwate, Miyagi and Aomori had joined the aquaculture of the European species.

But they all abandoned the effort after realizing they could earn higher net profits with the Pacific oyster. At the time, they did not have the technology to grow the European species big enough to fetch good prices in the market.

European flat oysters and their seeds were preserved, but they were all lost when the tsunami spawned from the 2011 Great East Japan Earthquake swamped the coast of the Tohoku region.

In Yamada town, local aqua-farmers ended their trial cultivation much earlier, when a tsunami from a powerful quake swept away oysters and oyster seeds in 1994.

The destruction caused by the 2011 tsunami convinced everyone that the European variety was lost forever.

But in April last year, an image of an unfamiliar oyster popped up on Instagram. The photo, posted by an oyster farmer in Yamada, captivated Sayaka Teramoto, a researcher of shellfish with the Iwate Fisheries Technology Center’s breeding and aquaculture department.

It was a flat and oval bivalve that was definitely not a Pacific oyster.

The farmer wrote that the strange oyster was attached to Pacific oysters he had cultivated, and that he kept the strange variety in a basket hanging from a pier.

Teramoto grew up in Rikuzentakata, a coastal city to the south of Yamada, and collected shellfish on the beaches since she was 3.

After the 2011 tsunami swept away her home, she pursued a career as a researcher of marine science.

Teramoto studied the Instagram oyster after it was provided by the farmer. A DNA analysis showed it belonged to a family of the European flat oyster.

The finding prompted Teramoto and Toshimasa Kobayashi, chief of the breeding and aquaculture department, to run a survey of 24 fishery cooperatives in Iwate Prefecture to ask if they had seen the variety in recent years.

The survey found the European flat oyster was confirmed in seven bays in the prefecture, including those where the bivalves were not cultivated previously. That suggested their habitat was expanding.

They were sighted more often in 2022 and 2023 than in other years, some farmers said.

According to a study, adult European flat oysters can survive in seawater even at 30-degree temperatures.

Water along the coast of Iwate Prefecture rarely exceeds 30 degrees, despite a spike in recent years, making it an environment where the bivalves can thrive.

A French restaurant in Kamaishi in the prefecture held an event in November offering samples of European flat oysters. Participants made positive comments.

One commented that the texture of the flat oyster is distinct from that of the Pacific oyster. Another said a new menu could be created with the European variety.

Teramoto, who was not a particular fan of consuming the oyster before, praised the taste after sampling one.

Hidenori Yoshida, adviser to General Oyster Inc., Japan’s largest chain of oyster bars, said the European flat oyster has the potential to break into today’s market.

“It is crisp and tastes dense,” he said. “The flat oyster can be a new offering and served during the months when the Pacific oyster is not in the market.”

Since overall demand for oysters has grown and their prices are higher, cultivating the European flat oyster will “make a good business,” Yoshida added.