Although Biwa pearls are not always round like their saltwater counterparts, they come in a variety of colors and shapes, and they were considered valuable enough in the late 1930s to launch a successful pearl industry along the lake’s southern shores.

In the decades after World War II, Biwa pearls dominated the global market. At that time, many Japanese consumers knew little of their country’s production of freshwater pearls, for the best places to sell high-cost luxury items were, until relatively recent times, all located abroad.

In particular, Jinbo Pearls based in Otsu, Shiga Prefecture, distributed to the boutiques of Europe and North America, providing a living for countless pearl cultivators on the lake. Lake Biwa pearl production peaked in the early 1970s at just over 6,000 kilograms annually, while the annual value of exported pearls peaked a decade later at around ¥40 billion.

By the end of the 1980s, however, the Biwa pearl industry had collapsed. Those close to the sector typically cite two main factors.

First, domestic freshwater cultivators faced increasingly strong competition from China. Interestingly, Chinese cultivators are believed to have picked up the tissue-nucleated technique as part of cultural exchange programs between the two countries.

“Japan had exchange programs with China at the time,” says Seki Shinsuke, a fisheries civil servant in Shiga Prefecture. “We taught them the technique, perhaps unaware of the implications. In fact, we might have even sent experts to China to help them out.”

As a result, China’s freshwater pearl industry flourished. Initially, Chinese freshwater pearls were inferior in quality, earning the nickname “Rice Krispies” for their irregularities.

Over the years, however, the techniques of Chinese cultivators have been refined to the point that China’s best freshwater pearls now rival their Lake Biwa counterparts.

The Biwa pearl industry has also been affected by a number of environmental issues. Freshwater mussels typically require a constant source of cool, clean water that is rich in mineral content. However, a multitude of water-borne pollutants from surrounding farms, industries and households end up in the lake, affecting water quality.

Higher average water temperatures due to climate change and damage to lagoons have also affected the lake’s ecosystem.

“I asked many to teach me the technique of cultivating mussels but we were all rivals at the time,” Hane recalls. “Eventually one or two locals kindly helped me get started.”

Hane and his family thrived on their mussel farm for a couple of decades. Once the market crashed, however, he accepted a position as a salaryman. It was a lifestyle that didn’t suit him.

Now 85, Hane still enjoys the outdoor life. “I’ll keep working this job as long as I’m able,” he says.

Five pearl farms are now operating at the south end of Lake Biwa.

Masakazu Saiki, who took over his elderly father’s pearl farm in Omihachiman, Shiga Prefecture, in 2016, says mussels develop in a symbiotic relationship with certain freshwater species such as catfish. In their larval stage, mussels are parasitic, attaching to fish gills with hooks or suckers in the early parts of their life cycle, he says.

In 2016, however, algae blooms were covering large areas of Lake Biwa’s surface and the fish — and, by extension, the mussels — struggled to survive.

It takes one or two years to raise mussels before they can be grafted. Now, however, less than 1 percent of pearly mussels develop into adulthood via this process. Pearl farmers are now working with researchers to find better ways to raise mussels.

“It’s tough to make a living,” Saiki says. “We have to figure out a way to bring more mussels into adulthood.”

Teams at the Institute for Humanity & Nature in Kyoto and the University of Shiga Prefecture jointly conduct research into lagoon ecosystems in Kusatsu, the birthplace of freshwater pearl farming.

Researcher Tohru Ikeya describes how he works alongside locals to discuss lagoon restoration. A long-term rehabilitation project by Shiga Prefecture has just been completed to resume the utilization of those lagoons.

“Lagoons are important as they tend to have adequate nutrients for efficient primary production. They’re calm and have gentle waves,” Ikeya says.

Once sewage disposal facilities have been installed upstream, it might be possible to regain control of a steady inflow into the lagoons.

Local residents are already starting to see some parts recover.

“In the past, farmers and locals could navigate waterways by boat,” Ikeya says. These environmentally sound ways to get around still exist in a few places.

The climate crisis is an ongoing problem.

“The rise in temperatures is altering the lake’s balance,” Saiki says. “Last summer, the temperature of the lake’s water reached 30 degrees Celsius — a record high.”

Saiki’s father, Isao, adds that today’s shells are thinner and weaker than shells of the past.

“Pearls of the past were better quality because the mussels themselves were healthier,” Isao says.

While researchers and farmers are fighting to save the pearl industry, there are some who would like nothing more than to see its demise. Jason Baker, senior vice president of international campaigns for People for the Ethical Treatment of Animals, believes pearl farming is unethical and exploitative. Baker admits we can’t be certain mollusks feel pain when an “irritant” — a term used frequently in the nucleated pearl farming industry — is inserted but wants people to “err on the side of compassion.”

He says there’s “an endless selection of jewelry that doesn’t harm animals or the planet.”

Syuhei Ban, a professor of plankton ecology at Shiga Prefectural University, counters by explaining that pearl cultivation is a natural process.

What’s more, bivalves die as soon as the shells are pried open and, therefore, do not suffer during harvesting.

“Local residents in Kusatsu hold a memorial ceremony for the mussels that are killed,” Ikeya adds. “And they teach children to respect living things in elementary school.”

While harvesting pearls does cause the mollusks to die, the edible tissue is not wasted. Pearly mussels are generally not highly sought-after cuisine, but Saiki at least sells the edible parts to a restaurant named Yamajin in the city of Omihachiman, Shiga Prefecture.

Cruel or otherwise, related environmental issues are putting much more than pearl farmers and restaurants in danger.

In a National Geographic report titled “A freshwater mussel apocalypse is underway” in December 2019, Carie Arnold examines the tremendous value freshwater mussels play in keeping ecosystems healthy.

Nevertheless, “staggering numbers of freshwater mussels are dying (in the United States and Europe),” Arnold writes. Many have become endangered almost overnight.

Baker highlights the environmental damage that people’s taste for beauty has wrought, saying simply that “aquaculture has contributed to the destruction of natural pearl oyster beds.”

Indeed, Ikeya notes that a 2016 study found Lake Biwa’s wild mussels are “severely endangered,” while its farmed pearly mussels are struggling to reproduce.

Imperiled by a wide variety of environmental issues, Lake Biwa’s remaining pearl farms sit at a crossroads.

If farmers ultimately give up cultivating these balls of nacre, all future Lake Biwa pearls will once again be produced exclusively by wild mollusks.