Mass Fish Die-Off at Jatiluhur Dam Highlights Environmental Challenges in West Java

A devastating mass mortality event at the Jatiluhur Dam in Purwakarta Regency, West Java, has claimed approximately 100 tonnes of fish, predominantly goldfish, causing an estimated financial loss of Rp 2.2 billion (US$134,000) for local fish farmers. The incident, which unfolded over the weekend, has prompted an urgent investigation by Indonesia’s Maritime Affairs and Fisheries Ministry, with early indications pointing to extreme weather and a natural phenomenon known as upwelling as the likely culprits.

The scale of the loss has sent shockwaves through the region’s aquaculture community, already grappling with environmental challenges and overcapacity at the dam. With around 44,000 floating fish farms currently operating—nearly four times the recommended limit of 11,300 units—the incident has reignited debates over sustainable fish farming practices in one of Indonesia’s key freshwater reservoirs.

A Perfect Storm of Environmental Factors

On Monday, officials from the ministry’s Directorate General of Fish Farming, alongside personnel from the Purwakarta Animal Husbandry and Fisheries Agency, descended on the dam to collect water samples for analysis. While the investigation is ongoing, initial theories centre on the role of upwelling—a phenomenon where shifts in wind direction cause deeper, oxygen-poor waters to mix with surface layers, suffocating fish that rely on higher oxygen levels near the top.

Ujang Komarudin, the ministry’s Director of Freshwater Fish Farming, highlighted the impact of recent weather patterns in the area. “Heavy rain and strong winds over the past week likely contributed to a drop in water temperature, exacerbating the effects of upwelling,” he explained, as reported by Antara on 10 February 2025. Goldfish, which are particularly sensitive to fluctuations in dissolved oxygen, bore the brunt of the die-off.

Fish farmers at Jatiluhur Dam reported days of relentless rain and gusty conditions prior to the event, aligning with broader patterns of extreme weather across Indonesia this rainy season. Intan Riyani, Head of the Farming Department at the Purwakarta Animal Husbandry and Fisheries Agency, noted that upwelling is a recurring issue at the dam during this time of year. “This isn’t a one-off event. The rainy season often brings conditions that trigger mass fish deaths,” she told Tribunnews on 10 February 2025.

Overcrowding and Pollution: A Deeper Crisis

Beyond weather-related triggers, systemic issues at Jatiluhur Dam have amplified the crisis. Overfishing and the sheer density of floating fish farms have long been flagged as threats to the reservoir’s ecosystem. According to Intan, the excessive number of farms contributes to pollution through fish feed runoff, which degrades water quality and heightens the risk of mass mortality events.

“The ideal number of fish farms here is around 11,300, but we currently have 44,000 units. This overcapacity strains the reservoir’s resources and makes events like this more likely,” she warned. Efforts are underway to reduce the number of farms, though progress has been slow. The ministry had issued advisories as early as November 2024, urging farmers to harvest their stock early to mitigate risks during the rainy season. However, many chose to delay in hopes of fetching higher prices for larger fish—a gamble that has now cost them dearly.

In the wake of the die-off, authorities have called on farmers to harvest all remaining fish, particularly goldfish, and to suspend farming activities until water quality and weather conditions stabilise. They have also stressed the importance of proper disposal of dead fish to prevent further contamination of the reservoir, a critical water source for both agriculture and human consumption in West Java.

A Regional Pattern of Loss

The tragedy at Jatiluhur Dam is not an isolated incident. Earlier this month, thousands of tilapia perished in fish ponds at Ngebel Lake in Ponorogo Regency, East Java, due to similar weather-driven upwelling. In that case, strong winds brought sulfuric deposits from the lakebed to the surface, poisoning the fish and inflicting losses worth millions of rupiah on local farmers.

Just last month, floating fish farms at Maninjau Lake in Agam Regency, West Sumatra, reported the death of 25 tonnes of tilapia, with losses estimated at Rp 625 million. Again, extreme weather and upwelling were identified as the primary causes. These repeated incidents underscore a troubling vulnerability in Indonesia’s aquaculture sector, particularly in regions reliant on freshwater lakes and reservoirs for fish production.

Economic Fallout and Livelihoods at Stake

The economic toll of the Jatiluhur die-off is staggering. At Rp 22,000 per kilogram, the loss of 100 tonnes of goldfish translates to Rp 2.2 billion in direct financial damage—a figure that does not account for the broader ripple effects on farmers’ livelihoods, local markets, and supply chains. For many small-scale fish farmers, who often operate on thin margins, such a setback could be catastrophic.

Aquaculture plays a vital role in Indonesia’s economy, providing employment for thousands and contributing to national food security. West Java, with its network of dams and reservoirs like Jatiluhur, is a hub for freshwater fish farming, producing significant quantities of goldfish, tilapia, and other species for domestic consumption and export. Events like this not only threaten individual farmers but also expose frailties in the sector’s resilience to environmental shocks.

Towards Sustainable Solutions

The mass fish die-off at Jatiluhur Dam has cast a spotlight on the urgent need for reform in Indonesia’s aquaculture practices. Reducing the number of floating fish farms is a critical first step, though it will require careful coordination to avoid displacing farmers without alternative income sources. Investments in water quality monitoring and early warning systems could also help mitigate the risks posed by upwelling and extreme weather, giving farmers time to act before disaster strikes.

There is also a pressing need for greater education and support for fish farmers, many of whom lack the resources or knowledge to adapt to changing environmental conditions. Government initiatives to promote sustainable farming techniques—such as regulating fish feed to reduce pollution or diversifying species to include those less sensitive to oxygen fluctuations—could build long-term resilience in the sector.

Speculative estimates suggest that if current trends of overcrowding and pollution continue unchecked, mass mortality events could become more frequent, with cumulative losses running into tens of billions of rupiah annually across Indonesia’s freshwater reservoirs. While these figures remain unconfirmed, they highlight the potential scale of the challenge if proactive measures are not taken.

A Call for Action Amid Climate Uncertainty

As climate change intensifies, extreme weather events like heavy rains and strong winds are expected to become more common, posing an ever-greater threat to vulnerable industries like aquaculture. The incidents at Jatiluhur Dam, Ngebel Lake, and Maninjau Lake serve as stark reminders of the intersection between environmental degradation, climate impacts, and economic livelihoods in Indonesia.

For now, the focus at Jatiluhur Dam remains on recovery and prevention. The Maritime Affairs and Fisheries Ministry’s investigation will provide crucial insights into the precise causes of the die-off, potentially shaping future policies to protect farmers and the environment alike. In the meantime, the affected communities face the daunting task of rebuilding after a loss that is as much ecological as it is economic.

The story of Jatiluhur Dam is a microcosm of broader challenges facing Indonesia’s natural resources and rural economies. Balancing development with sustainability will be no easy feat, but it is a necessity if such tragedies are to be avoided in the years ahead.