Jakarta Goes After Its Invasive 'Janitor Fish'

Cheers broke out in Indonesia's capital on Friday as residents, city workers, and environmental volunteers hauled bulging nets of invasive fish to the surface of a reservoir in an operation to crack down on "janitor fish." Authorities are seeking to remove at least 10 tons of the fish from Jakarta's waterways, reports the AP, an effort officials hope will restore balance to the Ciliwung River and renew public attention on water quality. From the polluted river to the concrete embankments and skyscraper-lined canals of the city's heart, the dark shapes of the fish cling tightly to the river walls. At first glance, they appear almost prehistoric, with armored bodies gleaming a dull brown beneath the murky surface.

Janitor fish, or suckermouth catfish, known scientifically as Pterygoplichthys and locally as "sapu-sapu," aren't native to Indonesia. Imported decades ago for aquariums because of their ability to consume algae, they were later released and found a home in Jakarta's heavily polluted rivers. The fish can grow up to 20 inches and live for 10 to 15 years. Experts have long warned that unchecked populations of invasive species can destabilize freshwater ecosystems, particularly in densely populated urban areas like Jakarta. Dian Rosleine, an ecologist from the Bandung Institute of Technology, said that the adaptability of janitor fish is very high, so that even in polluted conditions, it can survive when other species can't. "So, these fish are biological indicators that the water is in poor condition," she said.

The cleanup drive involved hundreds of personnel, including firefighters, disaster officers, and residents. They have netted and buried more than seven tons of janitor fish across the city within a week. The cleanup on Friday at a 19-foot-deep reservoir in East Jakarta's Ciracas neighborhood drew curious crowds as city workers collected about 700 pounds of the fish. Piles of wriggling janitor fish filled red barrels along the reservoir — tangible proof that something, at last, was being done. "The janitor fish populations have reproduced at a notable level while also feeding on native species," East Jakarta's mayor, Munjirin, told reporters when visiting Friday's cleanup. "The impact extends beyond ecosystem destruction, contributing to structural damage to riverbank and embankment walls."

Munjirin, who like many Indonesians uses a single name, vowed a review of the program after the Indonesian Ulema Council, or MUI, raised concerns over perceived cruelty, pledging that all fish will be dead before burial. While endorsing the cleanup, MUI's fatwa commission warned that burying the janitor fish alive amounts to a violation of animal rights enshrined in Islamic teaching. Meanwhile, experts caution that removal is only the beginning. Without improving wastewater management and reducing pollution, the river could quickly return to the same condition. "The Ciliwung River requires rehabilitation, our major challenge that must be addressed," Rosleine said. "Addressing the symptoms without tackling the root causes will not provide a lasting solution."