Media playback is unsupported on your device Media caption The BBC's Cindy Sui reports on the migrant fishermen paying high fees to work in Taiwan

The story of Yim Bun Then, a Cambodian rice farmer, is one you will not hear about when buying "Made in Taiwan" seafood at your local supermarket.

The 34-year-old is among 1,000 Cambodian men recruited by a Taiwanese-managed agency - Giant Ocean - from 2009 to work on mostly Taiwanese-owned fishing boats.

The workers were sent to waters off Africa as well as Japan, Fiji, Qatar and Malaysia. According to NGOs and the men themselves, they were promised $150 (£90) a month, but were paid about half that.

"I was forced to work almost 24 hours a day and never got paid my full salary. I was often whipped by my captain when I was sick and could not work or worked slowly," said Mr Yim.

The workers were not given enough food, he said, and during his two years at sea, the boat reached port just once - in 2012 in Dakar, Senegal. Transport boats took the catch to land.

"I never imagined I could return home because working on a fishing boat in the high seas, we only saw water every day. I couldn't even communicate with my family. My working conditions were like that of a slave," said Mr Yim.

In Senegal, Mr Yim called his brother, who told him to contact a Cambodian NGO - Legal Support for Children and Women (LSCW), which informed the International Organisation for Migration. The captain only allowed him to leave after learning about this.

Some 200 workers or their families reported similar treatment. "They could not do anything… If they wanted to escape, they would have had to jump into the sea," said Sokchar Mom, a LSCW programme manager.

Image copyright AFP Image caption Former Giant Ocean manager Lin Yu-shin (L) was jailed for 10 years in April

Taiwan is one of the world's top seafood exporters. Its products are sold worldwide to the tune of $2bn in annual exports.

But the recent trafficking case illustrates that despite its labour laws, its fishing industry exploits the migrant workers it relies on.

The case is not uncommon. The International Labour Organisation (ILO) estimates 21 million migrants work in forced labour each year, with 11.7 million working in Asia. Fishing workers are especially at risk - they work at sea and have less access to channels to seek help.

What is unusual about the recent case is that a Cambodian court in late April sentenced Giant Ocean's manager, Lin Yu-shin, and five associates to 10 years in prison, and ordered them to pay 150 victims between $1,750 and $15,900 each in compensation.

That case and others reveal serious loopholes in Taiwan's migrant employment safeguards, however, despite its positive rating in the US annual report on human trafficking.

Tata's story Filipino migrant Tata, 32, is one of many victims of labour exploitation and human trafficking in Taiwan. From a poor family, he signed a contract in the Philippines to work eight hours a day. But after arriving, he found the actual work hours much longer. "We start at 6 in the morning and end at midnight. We get 20 minutes for breakfast, lunch and dinner and we sleep for only five to six hours," said Tata, using his nickname. All day long, every day, he and other migrants each drop into the ocean and pull up a stone weighing 25kg (55lb) attached to a net used to collect coral when the boat is moving. The coral is used to make expensive jewellery Taiwan sells to tourists. Laws prohibit employers from making workers work more than 12 hours a day or 84 hours every two weeks, but Tata works three times that. "Before we go to sea, I pray to the Lord to make me strong," said Tata, whose passport is kept by the Taiwanese recruitment agency. Although his monthly salary is Taiwan's minimum wage of $634, half of it is deducted by the agency in the first year of employment, less in the second year. "Yes, it's very unfair... But because of our financial problems and [the fact] we cannot find other work, we stay," Tata said.

This is generating attention, because Taiwan is a major employer, attracting around 24,000 mainly Filipino, Indonesian and Vietnamese fishermen, but more if Cambodian and Myanmar workers hired through irregular channels are counted.

According to a draft summary obtained by the BBC of a soon-to-be-released report on Taiwan, the ILO called Taiwan's Fisheries Agency's system of management and protection of migrant fishers "loose and unregulated".

"Most notably, no minimum wage is provided and working hours and rest breaks are determined by the contract agreed to between the migrant fisher and the fishing vessel owner," it said.

Taiwan says its labour and minimum wage laws also apply to fishing boats - but some are registered overseas. And many owners of the 1,300 locally registered deep-sea fishing vessels prefer to hire workers from overseas, who never enter Taiwan.

"It's difficult to monitor them," said Chung Kuo-nan, a Fisheries Agency spokesman. "But they're required to report workers' information to the government and follow Taiwan's labour laws. If not, they could be fined."

Giant Ocean's boats were not. Taiwan's officials are quick to say it was an isolated case and the company was actually registered in Cambodia, not Taiwan. It has since shut down and could not be contacted.

But Giant Ocean had worked with local employment agencies and LSCW officials travelled to Taiwan last year to inform authorities about the company.

But a prosecutor in the Kaohsiung, southern Taiwan, where Giant Ocean's local office and staff are believed to have been based, said it could not investigate because the NGO had not supplied victims' testimonies.

Yet, it only took this reporter a quick Google search to find the NGO and get victims' statements.

Image copyright AFP Image caption Experts say human trafficking laws are not followed in Taiwan

Human trafficking

What is especially disturbing, local NGOs say, is that human trafficking - where large portions of salaries are deducted by agencies for repayment of a supposed recruitment debt by the worker - are happening right under local authorities' noses, but they are not taking a proactive approach.

"We've been telling the government for years, but they say these are disputes between employers and employees so it should be up to the two sides to resolve them," said Allison Lee, secretary-general of the Yilan Fisherman Labor Union.

Ms Lee said she had submitted paperwork for 100 cases to relevant authorities, but they wanted evidence such as time cards and payment slips, which do not exist.

"Some of the workers are sent back. Some are threatened with not being allowed back. Some are afraid to even admit they know me," said Ms Lee.

Image copyright AFP Image caption Migrant fishermen are forced to work like slaves on boats far out at sea

Taiwan is reluctant to admit human trafficking remains a serious problem, pointing to its positive US rating. Experts say this is based on laws that are often not enforced and that many cases fit the international definition of trafficking and forced labour.

Fishing is one of the big export industries for Taiwan; We need decent exported products, decent working conditions Sokchar Mom, Programme manager, Legal Support for Children and Women

Tsai Meng-liang of the Ministry of Labour's workforce development agency insists the government actively investigates reports of exploitation and has helped many workers recover owed wages. But prosecutions are rare and the amount recovered is minimal given the number of workers involved.

He blames overseas agencies for deducting excessive fees and says Taiwan has been working with their governments to stop the practice. But he agrees the government should make it easier for employers to hire workers directly, without using agencies.

Back in his village, Mr Yim is too ashamed to tell villagers or even his wife what happened to him.

LSCW, which has paid for him to be trained in chicken farming, urges governments to do more to fight trafficking.

"Even if migrant workers are not recruited in Taiwan, these are Taiwanese boats under their authority," Mr Mom said. "Fishing is one of the big export industries for Taiwan. We need decent exported products, decent working conditions."

The ILO has also urged governments, workers, employers, and civil society organisations to work together to ensure that the rights and interests of migrant fishers are protected.

Next year it will issue guidelines for countries to inspect boats at sea and to toughen penalties against violators. The US, meanwhile, is calling for more prosecutions.

Despite his sad story, Mr Yim is lucky. Other victims may still be at sea. Ms Lin's associates, meanwhile, remain at large.

The question is whether Taiwan's authorities will track them down and take concrete measures to stop exploitation in its fishing industry.