Decades of overfishing and the international demand for cheap seafood mean Thai boats are increasingly turning to slave labor as fishermen flee worsening working conditions, a rights group said on Wednesday. Thai waters are one of the world's most over-fished regions, and Thai boats now catch just 14 percent of what they caught in the mid-1960s, according to the London-based Environment Justice Foundation. To remain profitable, boats are forced to stay at sea for longer and go further afield than ever before. Some unregistered "pirate" boats are fishing the waters of other countries, also fueling demand for modern-day slaves, the EJF said in a report. As workers flee appalling conditions aboard the boats, catches decline and costs rise, vessel operators have resorted to using trafficked, bonded and forced labor to fill the shortfall and man their fishing boats, the EJF said. "Producers and consumers of Thai seafood are embroiled in one of the most outrageous social and ecological crimes of the 21st century," EJF executive director Steve Trent said in a statement. "Ecosystem decline and slavery exist in a vicious cycle," he added. Thailand is the third largest seafood exporter in the world, with exports valued at $7 billion in 2013, EJF said.