Campaign to kill invasive fish reveals contamination risks and chronic neglect of Java’s waterways.
Mass culls of sapu-sapu, an invasive South American fish thriving in filthy Jakarta rivers, are drawing attention to riverbank collapses, food-safety risks and the wider failure to clean up Indonesia’s heavily polluted waterways.
Invasion In Polluted Rivers
Introduced from South America decades ago as an aquarium “janitor fish”, sapu-sapu (suckermouth catfish or pleco) have colonised Java’s rivers after being dumped when they outgrew tanks. With few natural predators and an ability to survive in dark, oxygen-poor, foul-smelling waters, they outbreed native species, eat their eggs and dominate food sources, turning already stressed waterways into near monocultures.
Pollution, Holes And Collapsing Banks
More than half of Indonesia’s rivers are heavily polluted and two of its major river systems rank among the world’s dirtiest, with only about 7.4 per cent of municipal wastewater safely treated. In Greater Jakarta’s water‑stressed sprawl of 42 million people, sapu-sapu thrive by digging burrows into riverbanks to lay eggs, further weakening embankments that have in some cases collapsed, compounding flood and infrastructure risks.
Jakarta’s Killing Campaign
In recent weeks, Jakarta officials have mobilised residents, sanitation crews, fisheries staff and soldiers to net sapu-sapu in lakes and rivers, separate and release indigenous fish, then decapitate the invasive catch and bury them in pits. South Jakarta mayor Muhammad Anwar said about 5.3 tonnes of sapu-sapu were removed from local rivers in just two weeks, calling the fish a serious ecological and public‑health threat.
Toxic Fish And “Dangerous Snacks”
Scientific tests have found sapu-sapu flesh contaminated with heavy metals like lead and mercury and unsafe levels of E. coli, yet in some areas the fish are processed into cheap siomay (steamed dumplings) and pempek (fish cakes). Mayor Anwar has warned against eating such products, stressing that the fish “is dangerous to humans” and urging consumers not to be swayed by low prices that may conceal contaminated ingredients.
Activists Say Focus On Waste, Not Just Fish
Clean-river campaigner Gary Bencheghib, co‑founder of NGO Sungai Watch, calls the sight of thousands of sapu-sapu in rivers that look like “dark black, almost smelling like rotten eggs” “completely crazy”. Running 1,200 km from Bali to Jakarta to raise funds for clean‑ups, he argues that killing the fish alone misses the root cause: the solid waste and untreated sewage they feed on, and that only comprehensive pollution control will curb both the invasion and long‑term health risks.
The sapu-sapu invasion is less a freak ecological accident than a symptom of chronic pollution and weak wastewater management in Jakarta and across Java. Indonesians need sustained investment in sewage treatment, river clean‑ups and consumer vigilance over cheap fish products, while Singaporeans who share regional seas have a stake in upstream waste controls and cooperative efforts to keep invasive species and toxic contamination from spreading through shared marine and trade routes.
Sources: Straits Times (2026) , France 24 (2026)
Keywords: Sapu Sapu Fish, Pleco Invasion, Polluted Rivers, Heavy Metal Contamination, Dangerous Fish Snacks
