The first time I saw a whale shark in the water was at Ningaloo Reef, off the coast of Western Australia, in 2019. I was part of a research survey team documenting the annual aggregation. Nothing prepares you for the scale. You read that whale sharks can reach 18 metres in length and weigh 20 tonnes, but the numbers are abstract until you’re floating in the water and one passes beneath you - a spotted, grey form the size of a bus, moving with a grace that seems impossible for something so large.

Whale sharks (Rhincodon typus) are the largest living fish species. They’re filter feeders, consuming plankton, fish eggs, and small fish by swimming with their enormous mouths open or by actively sucking in water. Despite their size, they’re docile and pose no threat to humans. Divers and snorkellers can swim alongside them without danger, which has made them one of the world’s most sought-after wildlife tourism experiences.

But whale sharks are in trouble. The species was reclassified from Vulnerable to Endangered on the IUCN Red List in 2016, and population assessments since then haven’t improved the outlook.

Population Status

Estimating whale shark populations is inherently difficult. They’re highly migratory, covering thousands of kilometres across open ocean. They spend significant time in deep water where they can’t be observed. And they aggregate predictably in only a handful of locations, which makes it hard to know what the “total” population is doing based on observations at aggregation sites.

The most reliable population data comes from long-term monitoring at known aggregation sites. Ningaloo Reef in Western Australia has one of the world’s longest-running whale shark monitoring programs, operated by CSIRO and the Western Australian Department of Biodiversity, Conservation and Attractions. The Ningaloo data, spanning over 25 years, shows a relatively stable aggregation of 300-500 individuals visiting the reef annually, with some year-to-year variation.

However, stability at specific aggregation sites doesn’t necessarily mean global stability. Research published in 2024 by the Maldives Whale Shark Research Programme and others suggested that while some aggregation sites appear stable, the overall Indo-Pacific population may be declining by 5-6% per decade. The data is uncertain, but the trend is concerning.

In the Atlantic, whale shark sightings have declined at several historically reliable aggregation points, particularly in the Gulf of Mexico and the Caribbean. Whether this reflects population decline, shifts in distribution, or changes in environmental conditions that affect aggregation timing is not yet clear.

The Threats

Fishing. Whale sharks were historically hunted for their meat, fins, and oil in several countries, particularly China, India, Taiwan, and the Philippines. International protection under CITES (Convention on International Trade in Endangered Species) and national bans have reduced directed fishing, but illegal catches still occur. In 2024, reports from Southeast Asia documented ongoing illegal whale shark fishing in some regions, primarily for the fin trade.

Bycatch - accidental capture in fishing gear targeting other species - is a persistent problem. Purse seine nets used in tuna fishing regularly encircle whale sharks, which aggregate around the same bait fish schools that tuna follow. While many fishing operations now release whale sharks alive when they’re caught, the stress and potential injury from capture and handling can still be harmful.

Ship strikes. Whale sharks spend significant time at the surface, feeding on plankton blooms, which puts them in the path of commercial shipping. Documented ship strike injuries are common in areas where shipping lanes overlap with whale shark habitat. Research from the Marine Megafauna Foundation estimated that up to 25% of whale sharks photographed at some aggregation sites show scarring consistent with propeller strikes.

Plastic pollution. As filter feeders, whale sharks ingest whatever is in the water they’re filtering. Microplastic ingestion has been documented in whale shark faecal samples from multiple locations. The long-term health effects of chronic microplastic ingestion are not fully understood, but laboratory studies on other filter-feeding organisms suggest impacts on nutrition, gut health, and reproductive function.

Climate change. Changes in ocean temperature and circulation patterns affect the distribution and timing of plankton blooms, which directly affects whale shark foraging. Shifts in aggregation timing have been documented at Ningaloo and other sites, potentially linked to changes in the seasonal patterns of their prey.

Conservation Efforts

Australia. Whale sharks have been protected in Australian waters since 1999 under the Environment Protection and Biodiversity Conservation Act. The Ningaloo Coast is a UNESCO World Heritage site, and whale shark tourism is tightly regulated - boat operators must follow a code of conduct that limits the number of swimmers, approach distance, and interaction time. This regulatory framework is considered one of the best in the world.

Research at Ningaloo has been instrumental in understanding whale shark biology. Photo-identification (using the unique spot patterns on each shark’s skin) has allowed researchers to track individual animals over time. Some individuals have been re-identified at Ningaloo over more than 20 years, providing valuable data on site fidelity, growth rates, and survival.

Global tracking. Satellite tagging studies have revealed that whale sharks undertake long migrations across ocean basins. Tags attached at Ningaloo have tracked individual sharks moving north through Indonesian waters, across to the Indian Ocean, and as far as the coast of Africa. This transboundary movement means that protecting whale sharks at aggregation sites isn’t enough - they need protection across their entire range, which requires international cooperation.

The CMS Sharks MoU (Convention on Migratory Species Memorandum of Understanding on Sharks) provides a framework for international cooperation on shark and ray conservation, including whale sharks. Progress has been slow, but the framework exists.

Citizen science. The Wildbook for Whale Sharks is an open-access database where anyone can upload photos of whale sharks. The platform uses pattern-recognition algorithms to match photos to known individuals, building a global photo-identification database. As of early 2026, the database contains over 12,000 identified individual whale sharks from locations around the world.

This is genuinely one of the most effective uses of citizen science in marine conservation. Tourists, divers, and fishers contribute observations that professional research teams couldn’t collect alone. Every underwater photo of a whale shark’s flank is potentially a data point.

Tourism as protection. In many countries, whale shark tourism has created an economic incentive for conservation. In the Philippines, the whale shark tourism industry at Oslob and Donsol generates millions of dollars annually for local communities. In Mozambique, Mexico, and the Maldives, whale shark tourism supports both local economies and research funding.

This economic model isn’t without problems - some tourism operations use feeding or bait to attract whale sharks, which can alter their natural behaviour. But when managed well, tourism gives communities a financial reason to protect whale sharks rather than hunt them. At Ningaloo, the annual whale shark season generates an estimated $12-15 million in tourism revenue for the Exmouth and Coral Bay communities.

What’s Needed

Better data is the most pressing need. We still don’t have a reliable global population estimate for whale sharks. Photo-identification databases are growing, and satellite tagging is revealing migration patterns, but basic demographic questions - how many are there, how fast are they declining, what’s the reproductive rate? - remain poorly answered.

Stronger enforcement of fishing bans in countries where illegal catches continue is essential. CITES listing provides a legal framework, but enforcement depends on national capacity and political will.

Reducing bycatch in commercial fisheries requires changes to fishing practices, including the use of whale shark-release protocols in purse seine fisheries and modifications to gear that reduce the likelihood of entanglement.

And reducing plastic pollution and carbon emissions helps whale sharks alongside every other marine species. These are systemic problems that require systemic solutions, but they’re no less important for being familiar.

Whale sharks have been swimming the world’s oceans for approximately 60 million years. Whether they continue swimming them depends on decisions we’re making right now.