Dominance of Pleco Fish in Ciliwung River, IPB Expert: A Strong Sign That the River is "Ill"
The abundance of pleco fish (Hypostomus plecostomus) along the Ciliwung River does not reflect biodiversity richness but rather a strong indication that the river’s ecosystem is in critical condition.
Professor Yusli Wardiatno, a professor at the Faculty of Fisheries and Marine Sciences at IPB University, emphasised that the dominance of this invasive species mirrors the poor water quality, which has led to the loss of diversity in local freshwater fish.
“Currently, pleco fish is the easiest species to find in the Ciliwung, as if the river ‘belongs to it’. This dominance shows a fundamental change in the river’s condition, causing the loss of local freshwater fish diversity that was previously known to be high,” he stated, quoted from the IPB University website.
Unlike local fish that require clean water environments, pleco fish have an extraordinary ability to survive in extreme conditions.
The Ciliwung River, burdened by domestic waste, industrial effluent, and urban runoff, creates low-oxygen and turbid water conditions—uninhabitable for native species but a “paradise” for plecos.
Various studies have confirmed the presence of heavy metals such as lead, cadmium, and mercury in both the water column and river sediments. Pleco fish can survive in these conditions, making them the sole survivor dominating the waters.
Although economically viable, Prof Yusli issued a stern warning regarding the safety of its derivative products.
“Health risks remain even if the fish is processed into non-food products like feed, fertiliser, or industrial materials. Heavy metals could re-enter the food chain or be absorbed by plants through fertiliser if the processing is not thoroughly clean,” Prof Yusli explained.
Such utilisation must be accompanied by strict oversight, from capture locations to guarantees of final product safety, as many findings show that heavy metal levels in pleco flesh exceed safe thresholds.
Prof Yusli stressed that mass capture is only a short-term solution. The issue requires much more fundamental handling.
“Controlling plecos through mass capture and economic utilisation is merely a temporary solution. The dominance of plecos cannot be adequately addressed by that alone; it must be accompanied by river quality improvements and changes in public behaviour,” he concluded.
Improving river water quality and raising awareness to avoid introducing alien species into public waters are the main keys if Jakarta wishes to reclaim the glory of local biodiversity in the Ciliwung River flow.