DNA Research Traces Origin of Black Chin Tilapia Outbreak in Thailand

Scientists have long debated whether Thailand's black chin tilapia outbreak originated from a single source, and new DNA research from Chulalongkorn University's Department of Marine Science and Aquatic Resources Research Institute has provided definitive answers. Research published in the international journal Aquaculture Reports analyzed fish samples from every Thai province and compared their genetic profiles with West African origins, revealing 19 different genetic patterns—with three dominant patterns appearing in Samut Songkhram, Prachuap Khiri Khan, and Surat Thani provinces.

The genetic diversity strongly indicates multiple separate importations. Fish from Samut Songkhram matched at least two countries including Côte d'Ivoire and Ghana, while Surat Thani fish were genetically closest to specimens from Ghana, Togo, and Benin. Prachuap Khiri Khan and Phetchaburi fish showed yet different genetic signatures. The research confirmed that at least two genetic codes don't match fish from Samut Songkhram, meaning the province likely isn't the sole source of the national outbreak.

Human activity has clearly accelerated the spread, as genetically identical fish from Samut Songkhram have been found in distant provinces including Trat, Rayong, Chanthaburi, and Southern Thailand locations like Chumphon, Nakhon Si Thammarat, and Songkhla—distances impossible for natural fish migration. Beyond the legally permitted 2010 research importation, scientific evidence now confirms multiple illegal smuggling operations brought the fish into Thailand at different times. Key questions remain unanswered: who conducted these illegal imports, how many times did it occur, and what connections exist to the growing ornamental fish export business that shipped fish to 17 countries before the severe outbreak in 2017?