A recent series of whale and whale shark strandings across Indonesia has drawn attention to whether such events are becoming more frequent, with experts citing environmental changes, human activities, and increased reporting as possible factors.
Between September 12 and 25, five strandings were reported nationwide. Incidents included a whale shark found dead on a beach in Aceh province on September 25; a decomposed whale carcass discovered in a mangrove in Riau province shortly before; a dead whale in West Java on September 21; and two whale shark strandings in South Sulawesi and Bali earlier that month.
These occurrences reflect a broader upward trend in whale shark strandings documented over recent years. A 2025 study published in Scientific Reports, conducted by the Elasmobranch Institute Indonesia and Konservasi Indonesia, recorded fewer than ten strandings per year from 2011 to 2019. However, reported strandings increased to an average of over 22 annually beginning in 2020.
The study linked strandings to seasonal and oceanographic conditions, notably sea surface temperatures, wave height, and marine productivity in regions influenced by seasonal upwelling—a process where wind-driven currents bring nutrient-rich water to coastal areas, attracting feeding marine species closer to shore. Nonetheless, researchers noted that enhanced reporting driven by widespread smartphone and social media use might partially explain the rise in recorded cases.
Both whales and whale sharks are endangered species, underscoring the conservation concern raised by these recent deaths. However, scientists caution that it remains premature to establish direct connections among the five latest incidents.
Miftach Tjut Ade, chief of a traditional fishing community in Aceh province, described the September 25 whale shark stranding as unusual. Local residents attempted to return the stranded animal to the sea but were unable to move it due to its size. “It seemed to be accidental,” he said.
Experts highlighted the longstanding nature of strandings globally and the challenges in determining specific causes. Mark Meekan, adjunct senior research fellow at the University of Western Australia’s Oceans Institute, explained that historical strandings in remote Indonesian islands largely went unreported until recent technological advances facilitated rapid public dissemination.
Identifying causes is complicated by the condition of many carcasses. The whale found in Riau’s mangroves was severely decomposed, hindering precise identification, according to Ahlul Faldi, advocacy and campaign manager at the Indonesian Forum for the Environment. Official test results from the National Research and Innovation Agency were still pending. Faldi cautioned against speculation but noted that human activities such as seismic surveys, military sonar, high-intensity shipping noise, and marine pollution could disorient marine mammals.
Meekan added that strandings could result from echolocation errors, geomagnetic disturbances, or social behaviors that lead whole pods to beach themselves. For whale sharks, which are predominantly solitary slow-moving filter feeders frequenting surface waters, primary anthropogenic threats include ship collisions and pollution.
Whale shark researcher Brad Norman of Murdoch University warned against drawing conclusions without thorough case reviews. He also noted the difficulty in confirming a global increase in strandings and stressed that it was too early to determine the role of seasonal and oceanic factors.
Iqbal Herwata, senior manager at Konservasi Indonesia, observed that although the recent strandings occurred in historically affected areas, their timing differed from established patterns. He emphasized the need for further analysis of climate variability influences such as El Niño through comprehensive data on sea temperatures, currents, and marine productivity.
Meekan stressed the importance of addressing preventable, human-induced causes where possible. “For individual strandings where the cause is man-made, such as entanglement in fishing gear or pollution, the solution to the problem is in our hands,” he said.
Konservasi Indonesia is collaborating with marine conservation groups to enhance response efforts to strandings along Java’s southern coast, recognized as a hotspot for whale shark incidents.