A British environmental group says overfishing and the use of illegal and undocumented trawlers has ravaged Thailand's marine ecosystems and even encouraged the use of slave labor in the industry.

A report released Wednesday by the British nonprofit Environmental Justice Foundation says Thai fishing boats are now catching about 85 percent less than what they brought in 50 years ago, making it one of the most overfished regions on the planet.

Depleted fisheries in the Gulf of Thailand and Andaman Sea have, in turn, pushed Thai fishing boats farther and farther from home. Fewer Thais are willing to take on the dangerous, low-level work, so fishing operations use brokers and agents to enlist migrant workers from impoverished neighboring countries such as Myanmar and Cambodia, often through trickery and kidnapping.