After dark, fishermen waded down into the water wearing powerful headlamps, casting their nets over and over into the rough surf.

All night long, they shake the sludge from their nets and pick out the treasures: wriggling, transparent eels, each no thicker than a vermicelli string. They are worth their weight in gold, or nearly so. The fishermen put them in jugs, some of which they hang from ropes around their necks.

“Sometimes it’s gold, sometimes it’s mud,” said Dai Jiasheng, who has been fishing for glass eels in the winter for a decade. He is one of many fishermen like him who have attracted generations of people to Taiwan’s coast every year on the ocean currents.

But that appeal is waning.

“We used to think this business could make money, but now more and more people are not so sure,” Dai said.

Eel populations are declining worldwide. Conservationists say the most traded species is under threat.National Taiwan UniversityFisheries Science InstituteProfessor Han Yushan said that, like other places, overfishing hasThe Formosan eel’s population is already declining due to loss of its waterside habitat due to land development and, more recently, climate change.

In the 1980s and 1990s, Taiwan’s eel industry flourished due to Japan’s enthusiasm for eels. For a few years, Taiwan’s total exports to Japan alone reached US$600 million. But those days are gone forever.

Han Yushan said that although the impact of global warming on eels has not been carefully studied, Taiwanese fishermen believe that temperature changes will affect tides and thus affect their catch.

“The warmer the water, the deeper the fish will swim,” making it harder to catch them, said Kuo Chiung-ying, 68, president of the Taiwan Eel and Shrimp Exporters Association.

Fishermen like Dai Jiasheng sell eels to wholesalers along the Lanyang River in Yilan County, where signs clearly read “Buying Eels.” Wholesalers pay up to $40 per gram — about six eels — while gold costs around $63 per gram.

Before being flown to countries such as Japan, adult eels make their final stop in Taiwan, where they are placed in bags of water weighed down by ice at a packaging plant owned by Guo Qiongying in Taoyuan City in northern Taiwan.

A rare woman in a male-dominated industry, she strides through the factory in her overshoes on a winter evening, talking on the phone with clients and occasionally reaching into the pool to catch a swimming eel and sort it into a pipe.

Guo Qiongying entered the industry at the age of 21, working for a Japanese import and export company that dealt in eels and other products. She first saw eels when she was visiting a packaging factory as a translator. She was amazed to see that the workers could catch the eels with their bare hands and accurately judge their weight.

Guo Qiongying worked at the company for 17 years and lost her job when Japan’s bubble economy collapsed. In 1992, she started her own business, using all her savings to purchase factory equipment and mortgaging two properties. She said that for many years she spent the night in her car.

Eventually, such frugality paid off in a life of luxury: Guo now drives a convertible, the Taiwanese media reports on her life (and calls her the “Eel Queen”), and she once appeared on a Japanese TV show, cooking samples of her products for the judges.

“The Taiwanese eel won the competition,” she recalled with a laugh. “Our eel was just the best.”

Catching eels in the often-polluted estuaries is less glamorous, with fishermen standing for hours, dipping basket-like nets into the water again and again or tying themselves to metal anchors on the beach before swimming out further.

Chen Zhichuan, a part-time technician, said he almost died while fishing for eels in the water. “I didn’t have the strength to hold the rope. I let go and let myself drift in the sea,” he recalled while taking a break by the Lanyang River.

“Now that I’m older and more experienced,” said Chen, who was wearing a green rubber jumpsuit and yellow boots. “I won’t push myself to that extent again,” he said, before diving back into the surf.

Chen Zhichuan said he earned $8,000 this fishing season. Although it was not as much as in previous years, he was still quite satisfied.

During the epidemic, as restaurants closed and global shipping was in chaos, eel prices also plummeted.

Zhang Shiming, 61, used to fish for eels in his youth near Changhua City on Taiwan’s west coast. In the early 1990s, a giant petrochemical plant was built there. Massive chimneys spewed smoke and steam, and nearby grass was covered in white ash. He said the catch was no longer as rewarding as it once was.

“We’ve seen so much destruction over the years,” said Zhang, who switched to less labor-intensive clam farming about 20 years ago. “There are already very few eels this year.” At least, that’s what he’s heard;

His eldest son works at the chemical plant. “Just to make a living,” Zhang Shiming said.

Jiang Kaide, 43, a part-time construction worker, had been doing odd jobs for years until a friend persuaded him to try fishing for eels. He moved from his hometown to a village on the Lanyang River. He can only reunite with his four-year-old son and parents who visit him on weekends.

It has proven difficult to master the job, and the yield from nighttime eel fishing can be anything from 10 to 100. On a recent trip, he caught fewer than 20.

“It’s hard to make money,” said Jiang Kaide, who collapsed to the ground in exhaustion. “My whole family is counting on me.” He said he was about to give up the business.

“I think this is going to be unsustainable sooner or later,” he said.

Not far away, several retired elderly people were grilling chicken wings around a small earth pit, enjoying themselves. They were Amis, an indigenous ethnic group in Taiwan.

Eel fishing is not a tradition for the Amis, but the group has spent the winter in Yilan County for a decade. They camp in tents with wooden doors, and after fishing, they drink beer and chat until late at night.

“We come here not just for the eels, but to spend time with friends,” said Uwen Wayan, 58, as she found a dirty float to use as a stool. “This is one of the happiest times of the year.”

“We can’t control climate change,” she added. “All we can do is pray for good weather and a good harvest.”