Whale sharks congregate in hotspots across the world and tend to stay where there is food.
Camera IconWhale sharks congregate in hotspots across the world and tend to stay where there is food. Credit: Jess Leask

NASA star-finder tool tweaked to map thousands of whale sharks

THE social lives of whale sharks have been revealed in a 22-year study that tweaked a NASA star-finder tool to track the bus-sized creatures congregating at hotspots across the globe.

An international research team, including WA biologists, adapted an algorithm normally used to spot distant star patterns to identify and map more than 6000 of the world’s largest fish by their spots.

The study uncovered 20 locations, including Ningaloo Reef, the Maldives, Mozambique and the Red Sea, where the bus-sized sharks amass in predominantly male-dominated groups.

The researchers found that in the Galapagos 99 per cent of the whale sharks were female, compared to the Maldives and South Africa where 90 per cent of the animals were male.

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Murdoch University biologist and ECOCEAN director Brad Norman says the project chronicled 30,000 photographs of the sharks between 1992 to 2014, which showed that the fish tended to remain in the same place, with few moving between countries.

Whale sharks tend to stay where there is food researchers have found.
Camera IconWhale sharks tend to stay where there is food researchers have found. Credit: Jess Leask

“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,” Dr Norman says.

Whale sharks grow to about 12m in length, but are famously elusive and up until the 1980s there had been only 320 sightings worldwide.

The gentle giants eat mostly plankton and krill and they tend to travel to find food, researchers say.

The thousands of photos were collected from tourists and researchers into an online photo database called Wildbook for Whale Sharks, first created in 1995 by Dr Norman.

Researchers mapped whale sharks around the globe using tourists photo and a NASA star-finder tool.
Camera IconResearchers mapped whale sharks around the globe using tourists photo and a NASA star-finder tool. Credit: Jess Leask

“Engaging citizen scientists in photo identification also helps us to understand how ecotourism activities may affect the appearance and return rate of whale sharks,” Dr Norman says.

Dr Norman says the findings are vital for ensuring the right areas are protected for species conservation.

In the past century, whale sharks numbers have declined by 50 per cent and they were recently listed as endangered. Whale sharks are at risk from pollution, ship strike, fishing and being caught as by-catch.

Researchers mapped whale sharks around the globe using tourists photo and a NASA star-finder tool.
Camera IconResearchers mapped whale sharks around the globe using tourists photo and a NASA star-finder tool. Credit: Jess Leask

Study co-author and Murdoch University Fisheries Professor David Morgan says decades-long datasets are invaluable for predicting trends and changes in populations of species, and the whale shark database is crucial for conservation efforts.

While whale sharks are mostly found in warmer waters, where they go to mate and birth remains a mystery.

The study has this week been published in the science journal Bioscience.