‘They ate the shrimp, they even ate the crab’: Thai fishers count the cost of a voracious invader
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- Blackchin tilapia has spread to at least 19 Thai provinces since first being reported in Samut Songkhram in 2011, reaching from Bangkok's canals to the coastal waters of Pattaya and threatening to cross into Thailand's neighbors.
- Thai authorities have tried multiple control measures — releasing Asian sea bass predators, developing sterile-offspring variants, and paying people to fish for the species, removing thousands of tonnes — but experts including Thotsapol Chaianunporn of Khon Kaen University say the infestation is beyond eradication.
- Fishers have filed a lawsuit against agribusiness giant Charoen Pokphand Foods Plc, accusing it of introducing the invasive species; the company legally imported 2,000 blackchin tilapia in 2010 for breeding research but rejects the claims, saying all imported fish were destroyed.
- Blackchin tilapia is reshaping Thai ecosystems beyond competition for food and habitat: females dig courtship pits that increase sedimentation and the fish feed on zooplankton that controls algae blooms, risking wider harm to underwater plant photosynthesis, per Thotsapol.
- eDNA sampling — analyzing water for environmental DNA shed by organisms — is the most powerful monitoring tool for fish invasions, according to Dean Jerry of James Cook University, with newer tools like underwater facial-recognition cameras also under development.
- Restaurants and markets have tried commercializing the catch to control populations: chef Adisorn Jamsuksaward offers the fish free at his Kor-Tae seafood restaurant in Samut Prakan, and fermented fish sauce and animal feed products have been developed, but traders report weak consumer demand.
- Wallop Khunjaen, a Samut Songkhram shrimp farmer, lost nearly all of his million baby shrimp in two months as blackchin tilapia ate "everything" including crab; he has since abandoned shrimp farming entirely and no longer sees native fiddler crab.
Why it matters: For Thailand's 19 affected provinces and its neighbors, the blackchin tilapia invasion shows no signs of slowing, since rapid reproduction outpaces control efforts that have already removed thousands of tonnes. A pending lawsuit against Charoen Pokphand Foods now tests who bears responsibility for ecological damage already inflicted on shrimp farms and native fisheries. With eradication off the table, Thailand's ability to control spread and find economic uses will shape whether this becomes a regional crisis.
