I was not surprised to read NST's reports on alien predators in the rivers of Perak. (See NST 6th Oct). I have earlier commented on this in my posting on 13th August.
The NST reported that:
Local fish in ponds and rivers in Perak and the Klang Valley are in danger of being wiped out due to two highly aggressive predator fishes which are wreaking havoc in the waterways. Environmentalists have raised the alarm that if the biological invasion by the carnivorous peacock bass and the zebra cichlid (both from the cichlid family) is not checked, it will cause havoc on biodiversity and the livelihood of riverine fishermen. Where these two predator fish are found, they have moved to the top of the fish chain, even attacking the original "king" of Malaysian predator fish, the toman. That is why local fishermen are hauling in fewer toman, haruan, sebarau and udang galah.
These predator fish attack in groups and their prey are known to beach themselves in futile attempts to escape being eaten.
DHI Water and Environment Sdn Bhd environmental consultant Mohd Zambri Mohd Akhir is particularly concerned about the threat posed by the peacock bass.
"Now you can find these fish in Chenderoh, the most downstream dam in Perak. If it enters the other river systems in Malaysia that has unique local species, it is going to cause irreversible damage," warned Zambri.
He said the peacock bass was already robbing riverine fishermen of their livelihood as the problem had been around for nearly a decade.
"Fishermen in Batu Gajah and Tanjung Tualang are already facing this problem as their income has been steadily suffering over the years.
"The supply of udang galah is also greatly reduced, depriving fishermen of a decent income."
The peacock bass is from the Amazon in South America and can grow up to five kilogrammes. It breeds fast and protects its eggs and fry, giving it a high survival rate.
The zebra cichlid from Africa, however, only grows up to palm size, but is known for its notorious feeding habits.
Fisherman Ishanorzaman Jaimit from Kampung Gajah confirmed that there were many peacock bass in the mining ponds and rivers in Perak, but said that they only ate the small fish.
There is also increasing demand for the peacock bass. Fishermen get RM5 per kg for it, while the middlemen sell it for RM6.50 per kg.
The peacock bass is not usually available in restaurants but it is known to make it to the dinner tables of fishermen and anglers who catch it. 
Vincent Chin, owner of the Malaysian Fishing Net website, however, insists that the peacock bass is a real threat.
"It was brought into the country as an aquarium fish more than 10 years ago. It is a real nuisance because it feeds on local fish. They are vicious and attack like a pack of wolves," he said.
Another riverine fisherman, Muhammad Isa, said the zebra cichlid, nicknamed ikan belang for its distinctive stripes, was a bigger threat.
"The zebra cichlid is a bigger threat to the local species than the peacock bass," he said.
"In rivers and ponds in my area, the peacock bass is noted for eating only the perimpin (freshwater version of the ikan bilis).
Mohd Zambri Mohd Akhir warned that there were also other alien species in our waterways which were bound to pose problems in the future. He said the Fisheries Department should study potential threats from other alien species and ban the import of any species that could cause environmental havoc in our waterways. He pointed to the ban on the piranha and pacu species. Nik Mohd Rahimi, who manages the Fly Fishing and Lure Casting Centre in Taman Pertanian Bukit Cahaya in Shah Alam, agreed, blaming aquarium fish enthusiasts for the dire situation. He said the arapaima, the largest freshwater fish in South America, has been spotted in Putrajaya and Dengkil."When owners find it too costly to maintain the fish, they just release into the waterways." The government should make a rule to tag the imported fish electronically to prevent owners from disposing them wherever they like. See my earlier post on 17th August.
