A 10-meter-long whale shark weighing up to 1.5 tons that was found dead stranded on Garongan Beach, Panjatan, Kulonprogo, Indonesia in November 2023 has finally been buried. (Photo: RCTI+)
A recent study published in Scientific Reports has shed new light on one of Indonesia’s most puzzling marine tragedies: the repeated stranding of whale sharks along its vast archipelagic coasts. While previous reports often focused on how many of these gentle giants were found beached, this new research delves into why they strand — revealing a complex interaction of human activities, oceanographic changes, and biological vulnerabilities.
Whale sharks (Rhincodon typus) are the world’s largest fish, capable of growing over 12 meters long. Despite their massive size, they are filter feeders — peaceful plankton eaters that pose no threat to humans. Yet in recent years, their presence on Indonesian beaches has become a grim and frequent sight.
The new study, conducted by a team of marine biologists from several Indonesian and international institutions, analyzed over a decade of recorded strandings using field data, oceanographic models, and satellite imagery. The results suggest that whale shark strandings in Indonesia are not random events but are instead linked to ecological traps created by human activities and changing ocean dynamics.
Chasing Food into Dangerous Waters
One of the main findings points to a tragic irony. Whale sharks often follow dense patches of plankton and small fish — their main food source — into shallow coastal areas where the risk of stranding increases dramatically.
According to Mochamad Iqba Herwata Putra from University of Indonesia, the study’s lead authors, “These sharks are intelligent in their own ecological way, but their feeding instincts can override caution. When plankton blooms occur close to the coast, the sharks may follow the food right into estuaries or enclosed bays with limited escape routes.”
Indonesia’s coastal zones are undergoing rapid changes due to pollution, fertilizer runoff, and aquaculture. These factors trigger abnormal plankton blooms that attract whale sharks closer to shore. Once inside shallow waters, their massive bodies make it difficult to maneuver, especially in areas with strong tides, uneven seabeds, or low-oxygen conditions.
The Role of Human Activity and Climate Change
The study also highlights that ship traffic, fishing gear, and underwater noise play a crucial role in confusing whale sharks’ navigation. Vessel noise, especially from large cargo ships and fishing boats, interferes with the sharks’ ability to sense subtle water vibrations — one of their key orientation tools.
In regions like East Java, Maluku, and West Papua, frequent strandings correlate with heavy fishing activity. Researchers suspect that illegal fishing nets or barriers used in coastal aquaculture can unintentionally trap or injure whale sharks, preventing them from swimming back into deeper waters.
“Entanglement is often the first step toward a fatal stranding,” the report notes. “A disoriented or injured shark can quickly lose buoyancy control in shallow, warm water.”
Beyond human interference, natural forces driven by climate change are also at play. The Indonesian seas, located at the heart of the world’s Coral Triangle, are experiencing intensified upwelling, temperature fluctuations, and shifting current patterns.
Whale sharks are migratory animals that depend on stable thermal layers to navigate and locate food. Changes in sea temperature and salinity may alter the distribution of plankton, luring them into new — and sometimes perilous — areas.
Putra explains, “Our data suggest that certain stranding events coincide with El Niño years, when currents and nutrient flows change dramatically. The sharks follow altered food routes that can lead them into shallow zones they rarely entered before.”
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Ecological Traps and Coastal Development
The researchers use the term “ecological trap” to describe how whale sharks are unintentionally lured into dangerous environments created by humans. Coastal development — including harbors, fish farms, and tourism facilities — modifies natural coastlines and confuses the sharks’ environmental cues.
Artificial lights from coastal resorts and boats, for example, attract plankton at night. The sharks then follow this artificial food signal into bays or lagoons, only to find themselves trapped by receding tides.
“Light pollution in coastal waters is a silent killer,” says marine ecologist, Anindya Wirasatriya from Diponegoro University who was involved in the study. “It doesn’t just affect turtles or small fish — even giant species like whale sharks are misled by it.”
The study also incorporated satellite tagging of several whale sharks around Cenderawasih Bay, known as one of the species’ main congregation sites. Tracking data revealed that individuals often venture close to fishing platforms where anchovies are concentrated.
These fishing platforms, called bagan, use bright underwater lamps to attract fish. Whale sharks, mistaking the illumination for a rich food source, approach and sometimes collide with nets or ropes. While local fishers often feed them as part of ecotourism, researchers warn that such interactions can alter their natural behavior and increase stranding risk.
A Call for Coordinated Conservation
Experts argue that preventing strandings requires a coordinated strategy involving scientists, local communities, and policymakers. The study recommends several urgent measures: regulating underwater noise, limiting coastal light pollution, monitoring water quality, and establishing early warning systems in stranding-prone areas.
Indonesia’s Ministry of Marine Affairs and Fisheries (KKP) has already begun integrating community-based response teams to handle stranded whale sharks. However, prevention remains a challenge in a nation with over 17,000 islands and vast, diverse coastlines.
Putra concludes, “Whale sharks are indicators of ocean health. When they strand, it’s not just their loss — it’s a signal that our marine ecosystems are out of balance. The key is understanding and fixing the human-made traps that lure them to their deaths.”
The research ultimately reframes whale shark strandings as more than isolated tragedies. They are warnings from the ocean — signs of ecosystems strained by pollution, overfishing, and climate disruption.
As Indonesia continues to balance its maritime economy with conservation goals, scientists hope this study will inspire stricter policies and greater public awareness. Because saving the whale shark, they say, means saving the very balance of the seas they rule. (Sulung Prasetyo)
