22 years and counting – the two whale sharks calling Ningaloo home
NINGALOO REEF IS home to two of the longest studied fish in the world, with researchers having captured images of the marine giants returning to the World Heritage-listed area for over two decades.
The research is part of a photo identification program led by Dr Brad Norman and Associate Professor David Morgan from Murdoch University’s Centre for Fish and Fisheries Research, which aims to gather information on the mysterious animals.
Whale sharks – which were recently listed as endangered – travel to the warm waters of the marine park to feed from March to August, and are central to the region’s tourism industry.
The two in question – named Zorro and Stumpy by tourists due to the distinctive appearance of their tails – were first photographed in 1994 and 1995, respectively, when the program began.
“Some we may see only once, some maybe every three or five years, but these two have been seen almost every year for 22 years,” Brad explained, adding, “and it turns out it’s the longest monitoring of wild sharks in the world.”
By selecting an easily recognisable area – behind the gills on the left-hand side of the animal – photographs throughout the years could be compared to identify returning individuals.
Both Stumpy and Zorry have distinctive tail fins (pictured is Stumpy’s), which makes them easy to identify. (Image: Indian Ocean Imagery)
In 2003 the program expanded online, and has since gone global, with researchers based in a number of international sites where whale sharks are regularly sighted, and photographs being uploaded from 54 different countries.
Through advanced fingerprint-like spot-pattern recognition software, thousands of images from around the world have been analysed and compared, resulting in the identification of more than 1300 individuals in Ningaloo alone.
“It has been really successful,” said Brad.
The research was published this month in the journal Frontiers in Ecology and the Environment.
Understanding the endangered whale shark
Despite being the world’s largest fish, there are gaps in knowledge of whale shark’s biology and ecology, due to the cryptic nature of the animals – which up until the mid-1980s, had only been sighted 320 times.
This long-standing program, along with satellite tracking, will therefore aid researchers in learning more about the gentle giant, including identifying critical habitat for feeding and breeding.
“We’re starting to learn a lot more about these guys but there are still mysteries to be solved,” Brad said.
When researchers first saw Stumpy and Zorro, they were immature males, like most of the whale sharks found at Ningaloo, however, Brad said the appearance of their claspers now shows they have sexually matured.
“When they’re young they’re tucked up under their belly and smooth, then when they mature they become thick and elongated and rough and abrasive.”
“It indicates that somewhere along their travels they’ve mated, and it raises another question – where have they mated?”
Engaging the public
The world’s largest-known living fish, whale sharks were listed as endangered earlier this year.(Image: Indian Ocean Imagery)
The program has given the public the opportunity to be citizen scientists, and encourages people to upload their photographs to the growing library at whaleshark.org.
“The program is good in that it engages members of the public – it can be a tourist on a tour boat, a videographer out on the water or me on a tour boat or with a research group,” Brad said.
“Anyone who uploads their photo and it comes up with a match will get an email saying, ‘thanks for your help, the shark you saw was last seen five years ago,’ and the person who took the photo five years ago will also get an email.
“It keeps people engaged – it’s basically developed into the best monitoring program for whale sharks in the world.”
Brad has also initiated an education program where schools can raise money to sponsor a satellite tag and tracking costs – a total of $5000 each – and track their shark throughout its journey.
“Last year we got 16 schools involved and had 12 satellite tags out there on whale sharks, so it was a great success,” he said.
Schools can register their interest for ‘Race 2017’ at whaleshark.org.au/satellite-tracking
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