Blackchin tilapia, a fish native to west Africa, has been found in 19 provinces of Thailand, causing ecosystem damage and the decline of native species. The invasion has upended the livelihoods of shrimp farmers and coastal fishers, particularly in Samut Songkhram province south of Bangkok, where the fish was first reported spreading in 2011.
Local fisher Wallop Khunjaen was forced to abandon shrimp farming after blackchin tilapia ate nearly all of his million baby shrimp in just two months. “They ate everything. They ate the shrimp, they even ate the crab,” Wallop said. Native species such as fiddler crab have become less common, and he has stopped seeing some fish.
Spread and Control Measures
Blackchin tilapia has infiltrated at least 19 provinces, from Bangkok’s canals to the coastal waters of Pattaya, and officials fear it could cross Thailand’s borders. Thai authorities have increased control measures: releasing Asian sea bass as predators, developing sterile offspring, and paying people to fish for it. Thousands of tonnes have been removed, according to officials.
Experts say eradication is no longer possible. “We have gone far beyond the point that we can return,” said Thotsapol Chaianunporn, assistant professor at Khon Kaen University. Blackchin tilapia reproduces rapidly, juvenile fish have a high survival rate, and the species adapts to both brackish and freshwater conditions.
Economic Uses and Culinary Experiments
The most sustainable option, Thotsapol says, is to find economic uses for blackchin tilapia, such as animal feed or human consumption. Chef Adisorn Jamsuksaward at Kor-Tae seafood restaurant in Samut Prakan has been experimenting with the fish in Thai classics like tom yum talay and spicy larb salads. “People are hesitant, but once they try it – [they say] it’s delicious,” Adisorn said. He offers the fish free of charge to friends who request it.
Despite such efforts, few in Thailand want to eat blackchin tilapia. Tongta Samtia, a trader at a fish market in Samut Prakan, tried to sell it but nobody bought it. “They don’t know how to eat it,” she said, adding that it is not a beautiful fish.
Environmental Impact and Legal Dispute
The full impact on ecosystems remains unknown. Blackchin tilapia may degrade water quality as females dig pits in the sand during courtship, increasing sedimentation. This could affect benthic invertebrates and underwater plants. The fish also feeds on zooplankton, which controls algae blooms.
The source of the invasion is disputed. Fishers have filed a lawsuit against agribusiness giant Charoen Pokphand Foods Plc, which legally imported 2,000 blackchin tilapia for breeding research in 2010. The company says all imported fish were destroyed and rejects the claims, pointing to research that concluded the invasion was not from a “single introduction.”
Monitoring Tools and Future Threats
Researchers have developed new monitoring tools, including environmental DNA (eDNA) analysis, underwater facial recognition cameras, and acoustic tracking. Sampling eDNA is the most powerful tool, said Dean Jerry, distinguished professor at James Cook University. “Fish are particularly big shedders,” he said, likening a water sample to a “DNA soup” that can reveal entire fish communities.
Fishers and experts hope the invasion does not spread further. “It’s a silent threat,” said Thanandon Charoenhiransaku, a fishing-net seller and fisher in Bangkok. “You don’t notice until it’s there.”
