Invasive blackchin tilapia from Africa found in the waters of 13 Thai provinces were found to have come from the same parent stock, according to the Department of Fisheries.
The confirmation of DNA testing results comes amid stepped-up efforts by the department to eradicate the fish from local waters.
The department is also conducting research on sterilising the fish, starting with a pilot project in Phetchaburi on Wednesday.
Agriculture Minister Thamanat Prompow has established a special committee to oversee the eradication effort, with experts and representatives of people in affected areas.
Provincial committees will recommend regulations appropriate to their circumstances. This could include catching the fish and grinding them up to be used in feed or fertiliser, with guidelines for appropriate prices.
Two thousand blackchin tilapia were orignally imported from Ghana in 2010 by CP Foods, part of the Charoen Pokphand agribusiness conglomerate, according to Isra News Agency. The company had a permit to study the fish for breeding at its research centre in Samut Songkhram province.
The company subsequently told the fisheries department that the fish had died within three weeks of being brought to Thailand and had been buried. But they later started showing up in local waterways and as their population grew, native fish species started decreasing in number.
It was reported in 2017 that only around 50 of the original blackchin tilapia remained. DNA tests on those fish also confirmed they came from the original parent stock.
Guidance for dealing with invasive fish consists of three parts: making the best use of the fish, studying their life cycle, and sharing the knowledge with the community to keep the ecosystem balanced, said Dr Wanna Sirimanapong, an assistant professor of veterinary science at Mahidol University.
The protocols for regulating imports of alien species in Thailand are still ineffective, and a more comprehensive protocol is needed to prevent this kind of problem from happening in the future, Dr Wanna said.
Nattacha Boonchaiinsawat, a Bangkok MP with the Move Forward Party and vice-chairman of the committee, said the problem caused by the blackchin tilapia had become severe.
“Southern people are now worrying about the fish invading their waters. This problem could result in a 1-billion-baht loss in the aquatic economy,” Mr Natthacha said.
He said he would call representatives of CP Foods to explain the breeding experiment to the committee and answer questions about how the fish might have spread.
A resident of Bang Khun Thian district in Bangkok reportedly invested 300,000 baht in a shrimp pond that ended up being destroyed by blackchin tilapia. The farmer had to sell the land to pay off the debt. This reflected the severe impact of the problem, the MP said.
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