Malaysia’s ‘fish hunters’ target invasive species, one catch at a time

Puchong, Malaysia – On a recent Sunday morning, about a dozen men with fishing nets skirted the rubbish-strewn banks of the Klang River just outside the Malaysian capital of Kuala Lumpur.

Surveying the river, the men cast their nets into the polluted water. The nets billowed open and sunk quickly under the weight of metal chains.

From where they stood on the riverbank, they started to pull in their nets, already filled with dozens of squirming black-bodied catfish.

“You don’t see any other fish. Only these,” said Mohamad Haziq A Rahman, the leader of Malaysia’s “foreign fish hunter squad”, as they emptied their catch of wriggling suckermouth catfish into piles, away from the river.

None of the fish caught that morning were sold at nearby markets or food stalls. The sole purpose of the expedition was to cull suckermouth catfish, one among a growing number of invasive species that have in recent decades dominated freshwater habitats across Southeast Asia.

Once brought in for commercial or hobbyist reasons, invasive fish are not only threatening to edge native species out of the food chain in Malaysia and elsewhere, but they also spread diseases and cause great damage to local environments.

Invasive fish are a problem the world over, but experts say the issue is keenly felt in mega-biodiverse Malaysia.

“More than 80 percent of rivers in the Klang Valley have been invaded by foreign fish species, which can cause the extinction of the rivers’ indigenous aquatic life,” said Dr Kalithasan Kailasam, a river expert with the Malaysia-based Global Environment Centre.

“It’s growing in almost all other main rivers in Malaysia,” said Kailasam, explaining how species such as the suckermouth have the potential to quickly reproduce and survive in dirty water, leaving local fish on the losing side.