An invasive fish is threatening livelihoods in a northwestern Sri Lankan village by devouring traditional fish and shellfish species in the Deduru Oya reservoir, but local fishers aim to transform this challenge into an opportunity.

Over the past two years, fishermen have observed declining numbers of their typical catch while snakehead fish, previously unseen in Sri Lanka, have appeared in abundance.

According to local officials, the snakehead fish, common in Thailand and Indonesia, likely arrived with imported ornamental fish. When they outgrew home aquariums, owners probably released them into the reservoir.

Dr Kelum Wijenayake, a researcher studying the fish, explained that snakeheads have no natural predators in Sri Lanka’s ecosystem. “The Deduru Oya reservoir has provided them with an ideal breeding ground with ample food and no predator,” he said.

These fish can surface to breathe air and survive with minimal water. Their sharp teeth, powerful jaws, and aggressive feeding habits threaten the local ecosystem that has evolved over thousands of years, according to Wijenayake.

Snakeheads also grow considerably larger than native freshwater species. Fisherman Nishantha Sujeewa Kumara reported catching a 7kg (15lb) specimen, while native species typically weigh less than 1kg.

“Although we had heard of the snakehead fish before, none of us had ever seen one until a hobbyist angler came and caught it. That was the first time we saw it, because this fish cannot be caught using nets – it has to be caught by angling,” said Ranjith Kumara, the secretary of the area’s fishers’ association.

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“We started fishing in this reservoir in 2016. Back then, we used to catch small prawns and other high-value varieties, but now they’ve become very rare.”

Despite an angler competition organised to control the snakehead population proving unsuccessful, fishers see potential benefits.

Ranjith Kumara suggested promoting angler tourism as a sustainable control method that could provide alternative income for villagers who primarily depend on fishing and farming.

Fisherman Sujeewa Kariyawasam, who produces salted dried fish from the invasive species, noted that while fresh snakehead has limited market appeal, the dried version is flavourful and popular.

“I am working to further develop this business. As demand continues to grow, more snakeheads will be caught for production, which in turn will help control the spread of the snakehead population.”