PETALING JAYA: Our freshwater fish are being driven to extinction, while riverbanks are facing massive erosion which could pose risks to urban infrastructure, especially in major cities like Kuala Lumpur.The culprits in both cases is an invasive species of fish. Or three species, to be precise.
These fish burrow into the sand at riverbanks, destabilising them and causing erosion. When the river gets swollen during heavy rain, it could lead to the collapse of the banks.
In Kuala Lumpur, these fish are found in large numbers in the Klang River, Sungai Gombak and Sungai Batu, on whose banks stand many major buildings. They are also found in Sungai Kuyoh, Sungai Keroh and Sungai Jinjang.
In fact, more than 80% of rivers in Klang Valley been “plundered and permanently inhabited” by non-native fish, says Fisheries Department (DOF) director-general Datuk Adnan Hussain, who added that native aquatic life there is expected to become extinct soon.
The three species of suckermouth catfish, all commonly referred to as “ikan bandaraya,” are wreaking havoc on our rivers, and the consequences could be more devastating than initially thought, experts warn.
The species in question are the Hypostomus plecostomus (common pleco), Pterygoplichthys pardalis (Amazon sailfin catfish) and Pterygoplichthys disjunctivus (Vermiculated sailfin catfish).
“They dig holes in riverbanks to lay their eggs and shelter their young, weakening the soil. That leads to erosion and the collapse of the riverbanks,” says Prof Dr Mohammad Noor Amal Azmai, a professor at the Institute of Bioscience at Universiti Putra Malaysia.
He estimates that the suckermouth catfish population in Malaysia may have reached 100,000 across the peninsula.
“Can you imagine how many holes they have dug up? Easily tens of thousands if not hundreds of thousands,” he said. “Imagine what will happen when we have floods. It will be much worse.”
He added that the fish are also breeding uncontrolled because they have no natural predators.
Originally from the Amazon River basin in South America, these three species have made their way into Malaysian rivers, causing significant disruption to local ecosystems.
This is particularly problematic for densely populated cities like Kuala Lumpur.
In June, it was reported that over 700kg of ikan bandaraya was caught at Denai Sungai Kebangsaan, near UKM, during a programme involving 116 members of the Komuniti Pemburu Ikan Bandaraya. And that was just in one place.
“We need more efforts like this across Malaysia,” said Prof Noor Amal.
Biodiversity expert Dr Amirrudin Ahmad, a professor at Universiti Malaysia Terengganu’s Faculty of Science and Marine Environment shared his concerns, saying the fish accelerate soil erosion by disturbing riverbeds.“Over time, the holes they make destabilise riverbanks,” he said.
He added that in big cities, even minor changes in the stability of riverbanks can have significant consequences.
“It’s not an immediate crisis, but over time, these disturbances can add up, potentially affecting buildings and homes near riverbanks,” Prof Amirrudin said.
He believes a comprehensive study is urgently needed to assess the full impact of the suckermouth catfish on the environment, particularly in urban areas.
“We need to understand the scale of the damage they’re causing to determine the best course of action.”
Prof Amirrudin suggests a collaborative approach between the DOF, Irrigation and Drainage Department, as well as engineers to tackle the issue.
“Universities and government bodies already have the equipment and technology, including cost-effective methods like electrofishing, to manage the population of suckermouth catfish.”
Electrofishing, a technique that uses electric shocks to temporarily stun fish, is one such method that could help remove the invasive species from rivers in an efficient manner without harming other species.
The growing population of these fish, which can reach up to 600 grams each, also poses a threat to Malaysia’s biodiversity, particularly in the Gombak basin, he said.
“If left unchecked, these fish could disrupt the natural balance in our freshwater ecosystems.
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The DOF has previously expressed concerns about the ecological risks posed by the suckermouth catfish as they can be found infesting several Malaysian rivers.A previous DOF report in 2019 found that the fish’s burrowing behaviour is leading to muddy waters and the collapse of riverbanks, which destabilises the aquatic environment.
The DOF has also consistently urged the public not to release non-native species into rivers, warning that such practices can have long-lasting consequences for local biodiversity.
“It’s not too late to address this issue, but we need to act now,” said Prof Amirrudin.
“With the right resources and collaboration, we can mitigate the damage and safeguard both our urban infrastructure and our natural ecosystems,” he said.
