The Pesut and the Pinger: Using sounds to save river dolphins

One of the last 80 river dolphins in the Mahakam river © yk-rasi & yk-rasi / Budiono

By Danielle Kreb, Researcher, Yayasan Konservasi RASI

It is getting dark when the boatman finally steers our small boat towards home. As we motor between the green banks of Indonesia’s Mahakam river, I can smell the cooking fires and start to feel hungry too. It’s been a long, tiring day. But I am exhilarated rather than exhausted. After decades of searching for a solution, I think we have finally found one...

The answer, it seems, to the threat posed by fishing nets to the last river dolphins in Indonesia is a small, acoustic underwater deterrent: a pinger.

For over 20 years, I have dedicated my working life to the Irrawaddy river dolphins of Indonesia. ‘Pesut’ is the local name of our dolphin, and I know most of the 80 or so that are left. Every year, between 5-7 dolphins are born and around the same number die. That might sound like a stable situation, but it’s not: a population of 80 dolphins is far too small and vulnerable in the long run. Only by reducing the mortality rate can we hope to increase the population to the point where its future in the Mahakam is secure. But that would require tackling the greatest direct threat to the river dolphins – accidental entanglement in fishing nets.

My initial curiosity for the pesut was how this originally coastal dolphin evolved into a freshwater population, inhabiting the majestic Mahakam. But after my first personal encounter with the river dolphin, I got hooked. There is so much to learn about them; and their situation is so precarious. I didn't just want to study dolphins without offering solutions, and therefore I co-founded in 2000 our NGO Yayasan Konservasi RASI (Rare Aquatic Species of Indonesia).

With RASI, we have monitored dolphin deaths since 1995. We found that two thirds of them were caused by dolphins being caught in fishing nets. Since they are mammals, dolphins need to breathe air to survive. Entwined in a gill net and unable to reach the surface, they drown.

Personally, I would like to remove all fishing nets from the river and prevent any more dolphins from dying as by-catch. But local people need to fish. I know that very well. They are small-scale fishers, who rely on the river and use nets that are only 10-20 meters long. Overall, they do not cause harm to the river system, as so many others do. Their way of living is largely sustainable. Except when it comes to the accidental drowning of river dolphins.

That is why I feel so happy this evening, sitting in my boat and watching the sun go down. After two years of trials, supported in part by WWF’s River Dolphin Rivers initiative, it’s clear we’ve cracked it. Pingers definitely work: they protect river dolphins!

Fisher with yellow pinger © yk-rasi & yk-rasi / Budiono

Pingers are small electronic devices that emit a sound that is annoying to river dolphins. When they are attached to a fishing net, the dolphins stay 10-20 meters from the net - avoiding entanglement but still being able to feed in their favorite feeding areas. This has been proven by our studies and is echoed by local fishers, who say the dolphins no longer try to snatch fish caught in the nets. Despite the promise of an easy meal, the pingers warn them to keep their distance from the nets. If only we had known this years ago.

But the best – and most unexpected – part is that the fishers are happy too. By keeping the dolphins away, the pingers have reduced dolphin-damage to their nets and increased the average daily catch by 40%! It is the very definition of a win-win solution.

Indeed, after the trial all fishers wanted to keep the pingers and continue to use them, making me happy for the sake of the dolphins, and the sake of the fishers and their families.

But as I head happily for home, I have a new concern. This pilot has proven successful but we urgently need more pingers. In the trial, we were able to work with 33 fishers, but I would love to be able to provide pingers – permanently – to all men and women who fish by using gill nets in river dolphin areas.

And we also need to provide pingers to fishing communities along the other Asian rivers that are still home to other populations of endangered dolphins – including the Ganges, Indus and Irrawaddy.

It won’t be easy. But tonight, I step out of my boat feeling positive: we’ve found a solution and I am sure that we will find the means now to make it happen.

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Celebrating International River Dolphin Day - October 24, 2021

You can help us to save river dolphins by supporting our pinger crowdfunding campaign.

Just €4.50 will pinger-protect 1 meter of fishing net, while €70 will provide pinger coverage for an entire net. Please chip in to the Sounds of Safety crowdfunding campaign and then ‘ping a friend about pingers and ask them to help too.

Learn more about the WWF River Dolphin Initiative.