An international research project has modified a NASA algorithm designed to examine star patterns to analyse the distinctive spot patterns of whale sharks.
More than 30,000 photos of tourist encounters with the endangered species were sent to researchers by members of the public over many years. Scientists involved in the study then analysed the spots on the side of each whale shark to identify and track individuals.
The markings just behind each shark's gills and above their pectoral fin are completely unique, like a human fingerprint.
The NASA-inspired technology allowed a scan of a photo to be matched with a previous one.
Divers swim with a whale shark. Source: Aimee Jan
Lead author of the study and Murdoch University research associate Brad Norman said they've now identified 6,000 individual whale sharks across 54 countries, giving the scientists a rich data set to analyse and better understand the species.
"This effort is helping us to uncover the mysteries of whale sharks and better understand their abundance, geographic range, behaviours, migration patterns and their favourite places on the planet," he said in a statement.
Dr Norman, who is also the founder of non-profit organisation ECOCEAN, said using tourist photographs can also shed light on whether the sharks are returning to certain areas:
"Engaging citizen scientists in photo identification also helps us to understand how eco-tourism activities may affect the appearance and return rate of whale sharks.
"Perhaps there are ecotourism practices that are helping to ensure the whale sharks return that can be applied to other regions."
Males outnumber females
Whale shark numbers have decreased by 50 per cent over the last 75 years, resulting in their conservation status being upgraded to endangered last year.
Of the whale sharks identified in the latest research, 66 per cent were male.
A whale shark opens wide for a feed. Source: AAP
Researchers also identified 20 sites where whale sharks congregate, an increase from the 13 identified before the project began.
These hotspots include the Ningaloo Reef in Western Australia, the Atlantic coast of Mexico, Mozambique and the Philippines.
Dr Norman said observations of the whale shark population in these areas, and rarer sightings in others, suggest illegal fishing and lack of conservation can impact the whale shark gatherings.
The whale shark is the largest shark in the world’s oceans. It is thought they can grow up to 12 metres in length and live to about 100 years old.
Their main source of food is plankton and they are not known to pose a threat to humans.