Let’s Save our Rivers … from Ourselves

The health of many a Malaysian river is questionable, but it doesn’t get much worse than this: Sungai Tebrau in Johor has become so badly polluted that all marine life, save for a few resilient species of fish, has gone practically extinct in it. The cause of the pollution: the rampant dumping of their trash into the river by locals.

“Species like cockles and mussels can’t live in Sungai Tebrau because of the low oxygen environment,” Vincent Chow, vice-president of the Malaysian Nature Society, has been quoted as saying. “Only species like the non-native South American armoured catfish or suckermouth catfish can tolerate such an environment,” he added.

Nor is the problem of endemic pollution limited to this one river in Johor, of course. A tenth of the country’s once pristine rivers are badly polluted, accounting for more than 40 waterways, large and small. In fact, of the nation’s 473 rivers, only a half, or 244, are considered clean with the rest of them having been polluted to varying degrees.

In Penang alone, a recent survey has revealed that several local rivers – including Sungai Pinang, Sungai Jawi, Sungai Juru, Sungai Perai and Sungai Mas – are little more than smelly and unsightly stretches of putrid water. In decades past locals could bathe or go for a swim in these rivers; nowadays many of them would not want to go anywhere near them.

The African catfish can wreak havoc in Malaysian rivers. Photo Credit: YouTube

To make matters worse, it isn’t just pollution that has been wreaking havoc with local riverine ecosystems. Several rivers around the country have been colonized by invasive alien species, including African catfish, garfish, pirarucu, peacock bass, Chao Phraya high-fin giant catfish and tilapia. They are large predatory fish that prey on local species, decimating their ranks.

“Any minnow or fish that fits in their mouths will become prey and their voracious appetite helps them to grow to enormous sizes,” Amirrudin Ahmad, an ichthyologist at Universiti Malaysia Terengganu, told the New Straits Times. “The short span and narrow width of our rivers make it easy for predatory fishes to hunt for smaller fish like lampam, kelah, sebarau, kaloi, snakeheads (haruan, toman and bujuk), as well as the smaller Malaysian Clarias species (catfish),” he added.

The cause of such invasive species? You guessed it: us.

Hobbyists and fish growers have been wittingly or unwittingly introducing alien species to local rivers over the past decades, thereby upsetting native aquacultures and decimating local biodiversity.

At times fish cages get broken and alien fish species can escape into local rivers. Other times they might do so in floods by being washed away from ponds into nearby rivers. Often, meanwhile, people release such foreign fish into local rivers on purpose. Some people release their former pets when they grow too large; other people release fish, like African catfish, into rivers for religious reasons.

“Religious and cultural releases (bayar nazar) of African catfish, which can grow to an enormous size, by the community should be replaced with the release of indigenous species such as lampam, baung, kelah or the smaller local catfish,” the New Straits Times explains.

So there you have it: we continue polluting our rivers and we carry on endangering their health by allowing alien species to establish themselves in them. The solutions are simple: we must stop dumping our trash and sewage into our rivers. And we must stop contaminating them with alien species.

In other words, we can help rivers not just by what we do but by what we don’t do. There’s surely a lesson in that.