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Teenage whale sharks don't venture far to make sure they are fed: Aussie researchers

Updated: 11 16 , 2016 15:15
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SYDNEY, Nov. 16 -- Male adolescent whale sharks act just like human male teenagers, they don't venture far from home to makes sure they get their food, Aussie researcher published on Wednesday shows.

After sifting through over 6000 photos collected by citizen scientists and researchers at five whale shark aggregation sites over a decade, researchers from the University of Western Australia (UWA) and the Australian Institute of Marine Science (AIMS) found on average 35 percent of the over 1000 individuals were re-sighted at the same site in more than one year.

Interestingly, they found no sharks had travelled across the Indian Ocean, though one shark was tracked between regional localities from the Seychelles to Mozambique, suggesting links to occur, but populations are likely to be distinct.

"This is good news for our whale sharks," lead author from AIMS and UWA's Oceans Institute Samantha Andrzejaczek said in a statement on Wednesday, adding it appears whale shark movements are strictly regional.

"Whale sharks are under threat from human impacts of hunting and ship strike and it makes it much easier to plan for conservation if we only have to deal with neighbouring countries in each region rather than localities spread across the entire Indian Ocean."

Surprisingly, the researchers found male adolescent sharks at Ningaloo Reef on the north-western Australia coast didn't venture too far from home either, a habit of human teenagers.

"Our whale sharks at Ningaloo are mostly male teenagers, they don't become reproductive adults until they grow to sizes of more than eight metres in length and this is thought to take up to 30 years," Andrzejaczek said.

"Our young males don't seem in any hurry to move on from their feeding grounds at Ningaloo we have some individuals that have now been sighted here for 19 years and have even matured."

But more photos from more localities - especially of adult male and females - are needed so the models can give a better estimate of migration patterns for whale sharks, even at regional scales.

This is where the public can step in, Andrzejaczek said as many of the 6000 images sourced for the study were from tourists who snorkelled with the sharks.

"We even downloaded videos from YouTube to get identification shots," Andrzejaczek said.

"Social media provides a great source of science for charismatic animals like whale sharks and we hope to encourage more engagement across the Indian Ocean."

The research was published in the journal Royal Society Open Science.

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