Troubled waters: Jakarta battles deadly, invasive sucking fish

Jakarta is grappling with a significant environmental challenge as its waterways become overrun by the sapu-sapu, an invasive sucking fish from South America. The Straits Times reports on the grim reality faced by the city, where mounds of the fish carcasses are accumulating on riverbanks, a stark visual of an uphill battle against a fast-breeding species thriving in heavily polluted waters.

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That there are thousands of (sapu-sapu) fish in some of these river bodies, where, you know, the rivers are like dark black, almost smelling like rotten eggs... is completely crazy.

Originally introduced decades ago to keep aquariums algae-free, the sapu-sapu has found a perfect, albeit toxic, habitat in Java's rivers. Unlike in its native Amazon, the sapu-sapu faces few natural predators in Indonesia. It rapidly outbreeds and outcompetes indigenous freshwater fish, consuming their eggs and food sources. This ecological imbalance is compounded by the fish's surprising resilience in oxygen-poor, polluted environments, where they also weaken riverbanks by digging holes.

The consequences extend beyond the ecological. Residents and environmental campaigners are raising alarms about the foul odors emanating from the decaying fish and the potential health risks associated with consuming snacks made from sapu-sapu caught in these contaminated waters. Clean river campaigner Gary Bencheghib described the situation as "completely crazy," noting the sheer number of fish in rivers that are "dark black, almost smelling like rotten eggs."

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Killing sapu-sapu is not addressing the real problem, he added in a phone interview, nearly halfway through a 1,200km run from Bali to Jakarta to raise money for river clean-ups and having witnessed the crisis at several stops along the way.

While Jakarta has launched a campaign involving residents, sanitation workers, and even soldiers to kill the sapu-sapu, removing approximately 5.3 tonnes in just two weeks, activists like Bencheghib argue this is a superficial fix. He emphasizes that the real solution lies in addressing the root cause: the extensive pollution of the rivers. As The Straits Times highlights, Indonesia faces a severe pollution problem, with a significant portion of its rivers heavily contaminated and a very low percentage of municipal wastewater treated. The sapu-sapu's proliferation is a symptom of this larger crisis, a crisis that requires a comprehensive approach to water quality management rather than solely focusing on eradicating the invasive species.

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The real solution is cleaning up “the waste it lives off... that you find in these polluted waters,” said Mr Bencheghib, co-founder of the Sungai Watch NGO.