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chill ran down the writer’s spine upon witnessing the massive armoured catfish and African catfish caught by the Slingshot Fishing Malaysia Club (SFM) in the Klang River, right in front of a shopping mall here recently.
Each fish was as large as an adult male’s arm or thigh, with an average weight of six to ten kilogrammes (kg). The potential devastation if these species were left to dominate our river basins is unimaginable. What’s more alarming is that both species have a lifespan of over a decade and reproduce rapidly in large numbers.
“For me, this is no longer a minor issue but a national concern. I’ve been an avid angler for the past 20 years, and over that time, we’ve noticed that native fish like the toman (giant snakehead) and haruan (striped snakehead) are becoming harder to find, whereas they were once abundant,” lamented Azahar Khalid, a member of SFM who took part in the operation.
He added that during a previous operation, the group managed to capture over 200 kg of armoured catfish alone, excluding other invasive species found in the same river.
massive African catfish caught by the Slingshot Fishing Malaysia Club (SFM) in the Klang River recently. Photo by Muhammad Basir Roslan.
Founded in 2020, SFM has 100 members and uses slingshot or catapult techniques with darts to catch invasive fish, particularly the armoured catfish (Hypostomus plecostomus), native to South America.
“We use this harpoon-like method because the slingshot allows the dart to reach far distances, and the specially made metal darts can penetrate the thick scales of the armoured catfish. After that, we reel in the dart along with the fish,” explained Azahar, adding that his experience as an angler helps him identify fish species just by their surface movements.
He further elaborated that invasive fish caught are either sold to traders, disposed of, or turned into compost fertiliser.
HIGHLY ADAPTABLE
Describing the dominance of invasive fish species as a ticking time bomb threatening native river fish populations, Director-General of the Department of Fisheries (DoF) Datuk Adnan Hussain, said the issue is difficult to address because many people fail to understand the impact these species have on the country’s river ecosystems.
"Invasive fish refers to species not native to the area but introduced by humans for various purposes. For instance, tilapia and African catfish are brought in as protein sources, while koi and arapaima are kept as ornamental fish.
SFM members are among the clubs in Malaysia that are so active in catching migrant fish that disturb the river ecosystem. Photo by Muhammad Basir Roslan.
"The gambusia (mosquito fish) is used to control mosquito populations. Additionally, some invasive fish enter our waters unintentionally, such as through ship hulls or escape from aquaculture enclosures," he explained when contacted by Bernama.
According to him, invasive fish can be categorised into two types: those that do not cause harm, referred to as naturalised species, which have been economically beneficial to farmers, such as the Javanese carp and Siamese gourami.
"On the other hand, invasive species that disrupt ecosystems pose ecological risks that ultimately threaten ecological balance, as seen with the freshwater redclaw crayfish, which has proliferated in our ecosystems since its introduction over 15 years ago," he said.
Based on the Study of Alien Fish in Inland Waters of Peninsular Malaysia, the dominance of alien fish species primarily originates from commercial farming and ornamental fish like tilapia (Oreochromis mossambicus), African catfish (Clarias gariepinus), redtail catfish (Hemibagrus wyckioides), and armoured catfish.
Research by the DoF’s Glami Lemi Fisheries Research Institute also reveals that the armoured catfish, redclaw crayfish, and peacock bass are highly dominant in Peninsular Malaysia’s waterways.
Adnan noted that while official data on the impact of invasive species on local river fish landings is still being compiled, the DoF has received numerous complaints from fishermen about declining catches of high-value fish and damage to fishing equipment caused by invasive species.
"More concerning is the fact that invasive fish adapt easily to their environment, even in polluted rivers," he added.
LOOMING DANGER
Expounding on the issue, Adnan emphasised that the presence of invasive fish in our river ecosystems creates intense competition with native species for food, space, and breeding grounds.
“Invasive fish are more aggressive and reproduce rapidly, which can drastically reduce the population of native species. Predator species, in particular, prey on native fish, disrupting population balance.
"One such predator is the redtail catfish, which poses a threat to local species such as the temoleh (Probarbus jullieni), kelah (Tor tambroides), sepat (gourami), and freshwater prawns. This fish grows quickly, further compounding its threat to local species," he added.
Datuk Adnan Hussain.
Adnan also noted that some invasive fish burrow into riverbanks to create habitats and spawning grounds, altering habitat structures, affecting water quality, and indirectly damaging aquatic ecosystems. Moreover, invasive fish can carry diseases or new parasites that can harm native species, he said.
Among the diseases commonly associated with invasive fish are Edwardsiellosis (which can damage the liver and pancreas of fish), Columnaris (a disease that causes tissue decay in fish skin), and White Spot Syndrome, which threatens native species, he explained.
He warned that if left unchecked, invasive species could have a negative impact on the fisheries, aquaculture, and tourism industries, ultimately leading to economic losses for the country.
ENHANCED ENFORCEMENT
To tackle the issue, Adnan said the DOF has implemented various programmes, including regular studies and monitoring to assess the current status of waters affected by invasive fish species.
These inventory activities are conducted year-round in collaboration with state fisheries offices. Under the 12th Malaysia Plan (12MP), DoF has carried out 74 inventory activities nationwide, he said.
Fish such as armored catfish will usually be planted in a hole and reused as agricultural compost. Photo by Muhammad Basir Roslan.
“DoF has also actively implemented mitigation programmes, such as alien fish hunting initiatives. These programmes involve various stakeholders and target species like armoured catfish and redtail catfish. Since 2022, 15 such programmes have been organised, involving state governments, local communities, NGOs, associations, private companies, and universities,” he shared.
Adnan highlighted the positive results of awareness campaigns conducted among diverse groups.
“More citizens are now helping to reduce the population of invasive fish. For example, a community project in Sungai Kuyoh, Selangor, has shown impressive results, with invasive fish catches dropping significantly from 600 kg at one time to 159 kg more recently,” he explained.
From an enforcement standpoint, Adnan pointed out that the Fisheries Act 1985 and its accompanying regulations prohibit the import, sale, breeding, storage, or display of prohibited fish species without written permission from the Director-General of Fisheries.
Those wishing to undertake such activities must comply with specific conditions. Violations of the act carry penalties of up to RM1,000 in fines, imprisonment for up to one year, or both.
“Previously, the department focused on inspections and issuing warnings to premise owners possessing prohibited fish, urging them to obtain official permits from the department.
“However, starting in 2022, we adopted stricter measures. After providing sufficient awareness opportunities, we began confiscating prohibited fish,” he explained.
To a question on whether a fine of RM1,000 is sufficient, and what the DOF suggests to deter offenders, Adnan acknowledged that the amount is “not very significant” at present.
“However, we are considering the broader community, as some individuals may be unaware of periodic updates to the prohibited fish species list. Moving forward, the DOF may explore implementing a more appropriate fine that aligns with current circumstances,” he added.
SFM’s Azahar opined that the RM1,000 fine set by the DOF is sufficient, noting that the impact of invasive fish species causes long-term damage to the ecosystem.
“From my perspective, the issue of fines is subjective. What’s most important is raising public awareness about maintaining the sustainability of our rivers. Even if we impose a fine of RM10,000, irresponsible individuals will still release invasive fish into the rivers.
“The media needs to actively highlight this issue to make the public more aware. If anyone sees others releasing these fish, they need to speak up and not remain silent,” he added.
As of November 2024, DoF confiscated various prohibited fish species listed under Schedule 2 of the regulations, with an estimated value of RM24,552.
FOR THE FUTURE
Adnan said the DoF is taking various measures to ensure the sustainability of native species like the patin buah, kelah and freshwater prawns through breeding and reintroduction into their natural habitats.
A total of 13 native fish sanctuaries have been established to protect the habitats of these species. Under the 12MP, 23.9 million fish fry have been released into their original waters, supported by an allocation of RM1.5 million.
Additionally, Adnan shared that the department collaborates with universities to gain insights from researchers studying alien or invasive fish species.
“The Department of Fisheries also partners with NGOs and local communities to restore habitats, raise awareness, and educate future generations.
"Through these noble efforts, the department hopes to rehabilitate river ecosystems, transforming them into thriving habitats rich with life. This will provide a sustainable source of livelihood and priceless natural beauty for future generations to cherish,” he said.
