On a humid Tuesday morning in Central Jakarta, five men stood shoulder-to-shoulder in a cramped police van, their hands still smelling of river mud and fish scales. They weren’t drug traffickers or extortionists—they were fishermen, arrested for hauling in too many of a seemingly innocuous creature: the walking catfish, or ikan sapu-sapu. To the untrained eye, it’s just another bottom-feeder lurking in Jakarta’s murky waterways. But to ecologists, market vendors, and now city enforcers, this invasive species has become a quiet crisis—one that’s exposing fractures in Indonesia’s urban ecology, informal economy, and environmental governance.
What began as a routine patrol by Satpol PP—Jakarta’s municipal enforcement unit—uncovered a small but sophisticated operation. The men had been using modified drag nets in the Cipinang and Krukut rivers, targeting walking catfish for resale to warungs and street vendors across the city. By afternoon, authorities had seized over 80 kilograms of the fish, destined for frying pans and sticky sweet soy glazes in kampung eateries from Tanah Abang to Senen. The arrests were made under Jakarta’s 2021 Invasive Species Control Ordinance, which criminalizes the harvest, transport, or sale of Clarias batrachus without special permits—a rule rarely enforced until now.
But this isn’t really about five men with nets. It’s about what happens when a resilient, air-breathing fish—native to Southeast Asia but ecologically aggressive beyond its range—invades a city’s already stressed waterways. The walking catfish doesn’t just survive in polluted canals. it thrives. It walks across land during rainy seasons, colonizing new ponds and outcompeting native species like ikan lele (native catfish) and ikan mas (common carp). Its presence signals deeper trouble: nutrient overload from domestic waste, fragmented habitats, and a lack of coordinated watershed management.
“We’re seeing walking catfish densities in Jakarta’s eastern canals that are three to five times higher than in natural floodplains of Sumatra or Kalimantan,” said Dr. Rina Suryani, a freshwater ecologist at the Indonesian Institute of Sciences (LIPI), in a recent interview. “They’re tolerant of low oxygen, high ammonia, and even occasional sewage spikes. In ecological terms, they’re generalists—and that makes them incredibly hard to control once established.”
Their adaptability has turned them into an unlikely commodity. In the informal economy, where protein is expensive and regulation is lax, walking catfish fill a niche. A single kilogram fetches between 25,000 and 35,000 rupiah (~$1.60–$2.20) at traditional markets—cheaper than farmed tilapia or chicken. Vendors praise its firm texture and mild flavor, ideal for pepes (steamed in banana leaf) or goreng (deep-fried). Yet this very demand fuels the cycle: as long as there’s a market, there’ll be someone casting nets in the dark.
Historically, the walking catfish was introduced to Java decades ago, likely through aquaculture escapes or accidental releases from fish farms. Unlike more notorious invasives like the Nile perch or snakehead, it didn’t arrive with fanfare—but its impact has been cumulative. A 2020 study by the Bandung Institute of Technology found that in 12 of Jakarta’s 15 major canals, walking catfish now constitute over 60% of the biomass in fish surveys, displacing native species and altering food webs. Their burrowing habits also weaken canal embankments, increasing maintenance costs for the city’s already strained drainage infrastructure.
City officials acknowledge the dilemma. “We can’t criminalize poverty,” said Bambang Supriyanto, head of Jakarta’s Environment Agency, in a statement to Kompas last month. “But we also can’t let unregulated harvesting worsen ecological degradation or create false impressions of sustainability. What we need is a managed approach—perhaps even a licensed harvesting program that incentivizes removal while protecting water quality.”
Such ideas aren’t without precedent. In Florida, wildlife agencies have long encouraged the controlled removal of invasive walking catfish (also introduced there) through bounty programs and public fishing derbies. In Vietnam, where the species is native, it’s farmed sustainably in controlled ponds—proof that the problem isn’t the fish itself, but the context in which it thrives.
For Jakarta, the path forward may lie in reframing the narrative. Instead of viewing the ikan sapu-sapu solely as a menace—or a black-market commodity—city planners could explore integrating its management into broader urban resilience strategies. Imagine: community-led monitoring teams trained to report invasive species hotspots; biodegradable traps deployed in high-risk zones; or even partnerships with culinary schools to develop value-added products from sustainably harvested stock, turning a ecological liability into a source of green jobs.
Until then, the arrests in Cipinang serve as a stark reminder: in a megacity where rivers are often treated as open sewers, even the most adaptable life forms can become both symptom and symbol. The walking catfish doesn’t question for permission to survive. It just does. And in doing so, it forces us to confront what we’ve tolerated in our waters—and what we’re willing to change.
What do you think—should cities like Jakarta manage invasive species through enforcement, or is there room for innovation that turns ecological threats into economic opportunities? Share your thoughts below.
