In Samut Songkhram province, south of Bangkok, the shrimp pond that once held a million baby shrimp now hosts an invader. In two months, blackchin tilapia ate nearly all of them. “They ate everything. They ate the shrimp, they even ate the crab,” says Wallop Khunjaen, a local fisher who was forced to abandon shrimp farming. Native fish have become scarce; some species, like fiddler crab, he no longer sees at all.
The blackchin tilapia, native to west Africa, was first reported spreading in Thailand in 2011. Since then it has proved unstoppable, infiltrating at least 19 provinces – from the canals of Bangkok to the coastal waters of Pattaya, a tourism hotspot. There are fears it could cross Thailand’s borders.
“Invasive blackchin tilapia has devastated Thai shrimp farmers, with one fisher losing a million baby shrimp in two months.”
In Samut Prakan province, chef and restaurant owner Adisorn Jamsuksaward has found one way to make use of the fish that has invaded his pond: cooking it. He offers blackchin tilapia dishes free to friends. “People are hesitant, but once they try it – [they say] it’s delicious,” he says. Yet he admits it is unlikely ever to be a bestseller.
Thai authorities have increased control measures: releasing Asian sea bass as a predator, developing blackchin tilapia that produce sterile offspring, and paying people to fish. Thousands of tonnes have been removed. But experts say eradication is no longer possible.
“We have gone far beyond the point that we can return,” says Thotsapol Chaianunporn, assistant professor at the department of environmental science at Khon Kaen University. The fish reproduces rapidly, its juvenile survival rate is high, and it thrives in both brackish and freshwater. After any control effort, it quickly reasserts itself.
The most sustainable option, Thotsapol argues, is to find economic uses – turning blackchin tilapia into animal feed or food for humans. Fish invasions are a growing global threat, often linked to aquaculture or the aquarium trade. For now, Thai fishers like Wallop Khunjaen are counting the cost: a pond emptied, a livelihood lost, and a species that, as he told officials, “if it had feet, would climb up your fisheries department office.”