Sri Lankan Fishers Battle Invasive Predator in Freshwater Reservoir
Freshwater fishers in northwestern Sri Lanka are confronting a significant ecological challenge that threatens their traditional livelihoods, yet they're determined to turn this environmental threat into a sustainable opportunity. The Deduru Oya reservoir, once abundant with native fish and shellfish, has become the breeding ground for an aggressive invasive species – the snakehead fish.
The Unwelcome Invader
Over the past two years, fishermen working the Deduru Oya reservoir have witnessed a dramatic decline in their traditional catches while observing unprecedented numbers of snakehead fish appearing in their waters. This species had never been seen in Sri Lanka before, creating alarm among the fishing communities who depend on the reservoir for their income.
Local officials believe the snakehead fish, commonly found in countries like Thailand and Indonesia, likely arrived in Sri Lanka through the ornamental fish trade. The theory suggests that when these fish outgrew their domestic aquariums, their owners released them into the reservoir, inadvertently introducing a predator with no natural enemies in the local ecosystem.
Dr. Kelum Wijenayake, an academic researcher studying the phenomenon, confirmed that the snakehead fish sits at the top of the food chain in Sri Lanka's freshwater ecosystems. The Deduru Oya reservoir has provided them with ideal breeding conditions – ample food sources and no natural predators to control their population.
Adaptive Predator with Destructive Potential
The snakehead fish possesses several biological advantages that make it particularly threatening to native species. These predators have sharp teeth and powerful jaws, making them aggressive feeders capable of decimating local fish populations that have evolved over millennia.
Dr. Wijenayake noted their remarkable adaptability, explaining that they frequently surface to breathe atmospheric oxygen and can survive in minimal water conditions, needing only enough moisture to keep their bodies hydrated. This resilience makes them exceptionally difficult to eradicate once established.
The size difference between the invasive species and native fish is substantial. Fisherman Nishantha Sujeewa Kumara reported catching a snakehead weighing 7 kilograms (15 pounds), while traditional freshwater species typically weigh less than one kilogram.
From Ecological Crisis to Economic Opportunity
Ranjith Kumara, secretary of the local fishers association, described how the community first became aware of the invaders. "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," he explained.
The impact on local fisheries has been severe. "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," Kumara added, highlighting the economic consequences for villages where fishing and farming represent primary livelihoods.
Authorities attempted to control the snakehead population through an angler competition, but this proved insufficient. However, the fishing community has developed innovative approaches to transform this ecological problem into an economic solution.
Ranjith Kumara has proposed that authorities promote angler tourism as a consistent control method, which could provide alternative income streams for local villagers while helping manage the invasive population.
Meanwhile, fisherman Sujeewa Kariyawasam has pioneered another approach by producing salted dried fish using the invasive species. "Although fresh snakehead fish has relatively low market demand, the dried fish made from it is tasty and a popular delicacy," he noted.
Kariyawasam is expanding his business, recognising that as demand grows, more snakeheads will be harvested for production, creating a sustainable cycle that helps control their spread. This practical solution addresses both the ecological threat and economic needs of the local community, demonstrating how environmental challenges can be transformed into opportunities with creativity and entrepreneurial spirit.
