Basten Gokkon – A new study has mapped whale shark stranding hotspots in Indonesian waters over the past decade and linked their occurrence to oceanographic dynamics, providing a scientific basis for targeted, preventative conservation strategies.

In the study published in October, marine researchers from Indonesia and New Zealand identified locations with significant reports of stranded whale sharks (Rhicodon typus) across Indonesia between 2011 and 2023. They said long-term stranding records can fill key data gaps for migratory species, such whale sharks, and their analysis also revealed population demographics, trends and oceanographically driven stranding hotspots.

"Findings from this study show that stranding incidents exhibit clear spatial and temporal patterns, with specific hotspots and seasons when cases increase," lead author Mochamad Iqbal Herwata, a species conservation senior manager at Konservasi Indonesia (KI), the local affiliate of Conservation International, told Mongabay in an email interview.

The researchers documented whale shark strandings across Indonesia's diverse marine habitats, where monsoon-driven oceanographic processes create productive feeding grounds. They compiled 115 verified events from news-based sources using strict inclusion criteria. They analyzed spatial and temporal patterns with statistical tests and hotspot mapping, finding that strandings were often associated with high chlorophyll-A (indicating phytoplankton abundance), high waves, and low sea surface temperatures during the southeast monsoon and transitional seasons.

The scientists found that the studied whale shark stranding events across Indonesia revealed clear regional concentrations, with West Java and East Java provinces showing the highest numbers. Their analysis showed that live and freshly dead strandings dominated the records, and that burial and release were the most common response outcomes across provinces.

They also learned single strandings were far more common than mass strandings, and that mortality remained high despite a 71% release success rate. The study's authors wrote that hotspot analysis identified a major stranding hotspot along the southern coast of Java and revealed consecutive, sporadic and newly emerging hotspot locations that intensified in 2022-2023.

"This information can serve as a basis for the government to shift from a reactive approach to a more planned, risk-based prevention strategy," Iqbal said.

Managing stranded whale sharks is extremely difficult because these large animals can't survive long out of the water. The study highlighted the need for Indonesia to focus its resources on specific hotspots and seasons where strandings are most likely.

The study identified an alarming dominance of juvenile whale shark strandings in Indonesia, revealing severe risks to long-term population recovery and showing that upwelling-driven hotspots, combined with natural and human pressures, are key contributors that require deeper investigation. The study also showed that mass strandings frequently coincide with seasonal upwelling events, while human impacts such as fishing gear, ship traffic, and coastal pollution likely intensify these risks. It noted that stronger rescue networks could improve survival rates for the many stranded individuals initially found alive.

"Losing juvenile individuals means losing their long-term contribution to reproduction and population recovery," Iqbal said.

"The impact is not only felt locally but also affects the conservation status of whale sharks at the regional Indo-Pacific scale," he added. "If juvenile strandings continue to increase, the already critical chances of population recovery will become even smaller, putting even greater pressure on the species' survival."

Scientists warn that whale shark numbers have already dropped sharply worldwide, with the Indo-Pacific population losing more than half of its individuals in just a few decades. Although the exact causes of many strandings remain unclear, evidence points to plastic ingestion, fishing gear injuries, and sudden environmental changes as key factors that put whale sharks at greater risk.

Iqbal said the most important step is to prioritize these hotspot areas for thorough investigations that include consistent necropsies, water-quality and oceanographic analyses, and checks for harmful human activities such as fisheries, coastal development and environmentally unsound aquaculture.

"By gaining a deeper understanding of these contributing factors, the government can design more targeted mitigation strategies to reduce future stranding risks," he said.

Iqbal noted that improving response capacity was equally urgent, and the government must provide technical training, standard guidelines, and the skills needed to conduct necropsies and collect samples properly, especially in regions that face repeated strandings. The Indonesian government has sought to establish a network of first responders equipped with the knowledge and training to deal with strandings.

"The role of local communities living near stranding hotspots is crucial in whale shark rescue efforts, especially because time is the key determinant of whether a stranded animal survives," Iqbal said.

Unlike whales or dolphins, whale sharks can't breathe outside of water because they rely entirely on water flowing through their gills. When they get stuck in shallow areas or unable to move, their oxygen supply is immediately cut off. Their heavy bodies can also crush their internal organs in very shallow water or on land, causing their condition to deteriorate within minutes and making rapid local response critically important.

Iqbal said communities need stronger knowledge of whale shark biology because improper body positioning and stress from rough handling or loud noise could quickly worsen the animal's condition. He said teaching simple skills such as keeping the body upright, ensuring the mouth is unobstructed, reducing unnecessary contact, and slowly guiding the animal to deeper water could greatly increase its chance of survival. He added communities could also support long-term conservation by taking spot-pattern photos for identification, which help scientists track population origins and movement routes.

"Their role not only increases the survival chances of stranded individuals but also contributes to understanding regional whale shark populations and supporting long-term conservation efforts in Indonesia and the broader Indo-Pacific region," Iqbal said.

The researchers also suggested strengthening regional cooperation because whale sharks moving between Australia, Christmas Island and Indonesia pass through areas with high stranding risks, and the absence of shared identification data limits understanding of how these events affect connected populations.

They recommended creating a joint photo-ID database, sharing satellite-tracking and stranding information, establishing regional response protocols, and collaborating on research so countries can build a coordinated framework to reduce strandings and protect migratory whale sharks.

"This underscores that whale shark conservation cannot be carried out solely at the national level," Iqbal said. "The Indo-Pacific is an interconnected migratory system, meaning that the loss of individuals in one country can affect the entire regional subpopulation."

[Follow Basten Gokkon on X to see his latest work via @bgokkon.]

Citation

Putra, M. I. H., Wirasatriya, A., Asyraffauzan, H., Fahmi, Syakurachman, I., Hasan, A.,... Manessa, M. D. M. (2025). Spatio-temporal patterns, trends, and oceanographic drivers of whale shark strandings in Indonesia. Scientific Reports, 15(1), 36455. doi:10.1038/s41598-025-20543-3

Source: https://news.mongabay.com/2025/11/whale-shark-stranding-indonesia-marine-endangered-species