Fishers detonate a bomb every hour on one Indonesian coral reef

Within just a 17-kilometre radius in one Indonesian archipelago, there is an explosion almost every hour as locals practise “bomb fishing”, destroying coral reefs and decimating marine life.

Over 483 days between May 2023 and September 2024, Ben Williams at University College London and his colleagues deployed an acoustic monitoring system at Spermonde Archipelago, south-west of Sulawesi, Indonesia.

As well as being a global coral reef biodiversity hotspot, it is a location where fishers detonate explosives underwater, stunning and killing fish that can then be easily harvested.

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“The sound of bomb fishing is so loud that if you’re on a dive it can shake you out of your skin,” says Williams. “You feel it more than you hear it. But if you put your head up on the surface, you likely won’t even see the boat responsible because the sound of bomb fishing travels such a huge distance underwater.”

The recording equipment sat at a depth of 17 metres and was able to detect explosions inside a radius of almost 17 kilometres. The team used AI to analyse their 3650 hours of raw audio. They recorded 3567 explosions, or just over 23 per day while the device was underwater.

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“We have shown the true extent of this practice in a known hotspot for the first time ever, which we hope will drive action to curb this destruction,” says Williams.

One of the biggest issues is that there is an illegal supply chain underpinning the bomb fishing, usually involving the sourcing of fertilisers and fuses or detonators, he says. “In other regions these may be stolen mining explosives or even military explosives.”

Once the fishers have the explosives, enforcement at sea is sparse. “It’s like Whac-A-Mole targeting the bomb fishers. The best approaches should tackle the illegal supply chain that gets the materials needed to make explosives to bomb fishers or sellers of these,” says Williams.

Bomb fishing is a problem across the tropics, and part of the solution is retraining locals in sustainable tourism and reef restoration, he says. “It’s been documented in 34 countries, from South America to the Mediterranean to the East Coast of Africa and South-East Asia.”

Rinaldi Gotama, who wasn’t part of the work, is currently studying at the University of Queensland, Australia, and has worked extensively with Indonesian non-governmental organisations in reefs targeted by bomb fishing. He says he wasn’t surprised at the scale of the problem.

“I expected the frequency to be high, but studies regarding bomb fishing are relatively scarce because it is notoriously difficult to quantify,” Gotama says.

He says the new method employed by the researchers might help combat the practice. “If this acoustic method could be replicated elsewhere, it could help with detecting and quantifying blast fishing and help identify hotspots of activity,” says Gotama.

“That could be valuable not only for ecological monitoring, but also for targeting enforcement and evaluating whether management interventions are actually reducing blast fishing.”

Remote Sensing in Ecology and Conservation DOI: 10.1002/rse2.70093