The 'foreign fish' invading Klang Valley rivers

The presence of non-native fish in the country is usually due to individual hobbies, where people buy them at pet stores to be reared in aquariums at home.

A popular species of fish is the suckermouth catfish or common pleco, a tropical freshwater fish belonging to the armoured catfish family valued for its role as bottom cleaners.

Once they outgrow their aquariums, though, they are often released into rivers where they become increasingly aggressive.

In the Klang Valley, almost 80% of rivers have been monopolised by so-called foreign species, including the suckermouth catfish, red patin, black tilapias, and the north African catfish.

Anglers who reel in suckermouth catfish often leave them to die on the shore.

In one area at Sungai Langat, suckermouth catfish are often seen moving in groups and behaving aggressively towards local species such as temoleh and arowanas.

Armed with nets, volunteers have made it their job to hunt down and catch these foreign fish.

They begin working as early as 7am, spreading out over several kilometres.

Every once in a while, they pull in their nets to check on their catch.

One of them, Syahdani Danial (left), lifts a suckermouth catfish out of his net.

Others help pull in the heavy nets filled with more suckermouth catfish.

Such activities are necessary as the presence of foreign fish like these catfish poses a threat to the local ecosystem.

Today's work has resulted in some 700kg of fish being caught by about 100 volunteers.

Even children pitch in to weigh the fish. The data is then handed over to the research division of the fisheries department.

Some suckermouth catfish can weigh more than 1kg.

The volunteers also measure the length of each fish they catch.

The fish are then chopped into small pieces to be made into fish feed.

This is done by a machine which processes the meat into pellets.