Speckled with white spots and stripes in patterns as unique as a fingerprint, these colossal creatures are the largest – and one of the most awe-inspiring – fish in the sea. But despite their behemoth stature, whale sharks remain a mysterious group of ocean dwellers.
“Ok, go, go, go!”
Our dive guide gives the signal and we splash into the ocean from the back of the tour boat’s marlin board like a team of poorly trained synchronised swimmers. The water is cool but thanks to my wetsuit and a healthy dose of adrenaline, it barely registers. We’re treading water several kilometres from shore in the pristine waters of the World Heritage-listed Ningaloo Reef, waiting to catch a glimpse of the biggest fish in the sea.
On cue, 10 heads duck below the water and furiously scan around. It’s cloudy with plankton. Then, like a slow-moving speckled submarine, he swims towards us with graceful movements and a wide gaping mouth. He’s huge! Once his head has travelled past the group, our guide motions for us to start swimming. Despite his colossal body, he’s surprisingly fast and it’s hard work keeping up with him. He gives a nonchalant flip of his giant tail and disappears into the distance.
Snorkelling alongside whale sharks has become a ‘bucket list’ travel trend in recent years as word spreads about how amazing it is to see these gentle giants of the ocean in their natural environment.
Ningaloo Marine Park, off the north coast of Western Australia, is one of the few places in the world where it’s possible to witness the annual migration of whale sharks so close to shore. Although technically sharks, whale sharks are filter feeders like whales and return to the reef each year from March to July, after the annual mass coral spawning, to feast in the krill- and plankton-rich waters.
The number of people swimming with whale sharks each year at Ningaloo has ballooned from just 1,000 in 1993 to over 30,000 people in 2019. And it’s easy to understand why. Seeing these massive and mysterious creatures up close can be life changing.
Samantha Reynolds knows this first-hand. She was so captivated by whale sharks when she first swam with them in 2012, she returned to university at the age of 40 to study marine biology, and she’s been researching these enigmatic giants ever since. Reynolds is now a PhD Candidate at The University of Queensland and a research scientist with non-profit group ECOCEAN.
“It seems incredible to me that we still know so little about them,” Reynolds says. “We don’t know where they mate or where they give birth to their young, so there’s still so much to find out.”
What we do know, however, is that whale sharks are now a globally endangered species and Reynolds says their fate is pretty much all down to humans. “Whale sharks are vulnerable to ship strike because they spend a lot of time swimming in surface waters and in areas of high shipping traffic.” And in some parts of the world, whale sharks are illegally poached for their fins, and caught as bycatch by fishing trawlers.
But Reynolds says one of the greatest threats to whale sharks is climate change. “We need to reduce our carbon emissions because it’s creating warming of the oceans, but also ocean acidification,” she explains. “If the oceans are too acidic, the krill that whale sharks depend on for food are unable to produce their skeleton shells.”
Plastic waste in the ocean is also a problem. Reynolds says that because whale sharks are filtering huge amounts of water through their gills, they may not be getting enough food if there’s too much plastic in what they’re filtering.
Whale shark tourism is a booming industry around the world, but unfortunately not all operations are as well-managed as the one at Ningaloo Marine Park. Part of Reynolds’s PhD research is looking at the impact of the ecotourism industry at Ningaloo on whale shark movements and energy expenditure.
“They seem to be coming back in good numbers every year and don’t seem to change their behavior that much when people are swimming with them. We want to definitively show other places that this is a good way to do tourism with whale sharks, and to look to Ningaloo for world’s best practice.”
Wildbook for Whale Sharks, a global photo identification database pioneered by Dr Brad Norman, marine biologist and founder of ECOCEAN, is using space technology to monitor and track whale shark movements around the world.
“Brad teamed with a software engineer and a NASA astrophysicist to develop a program using a modified algorithm that NASA uses in the Hubble Space Telescope to map stars, in order to map the unique spot patterns of individual whale sharks,” Reynolds says. Just like human fingerprints, the pattern of white spots behind a whale shark’s gills is unique to each animal.
‘Citizen scientists’ around the world can upload their whale shark photo (with information about the sighting) onto the database and the software either matches it with an already catalogued whale shark or creates a new profile. Wildbook for Whale Sharks has so far logged more than 75,000 sightings of over 12,000 individually catalogued whale sharks. One of these 12,000 is Stumpy.
And just who is Stumpy? Reynolds says he’s the most famous whale shark on the Ningaloo Reef. He was first photographed in 1995 and he’s been coming back to visit every year since. He has the honour of being the first whale shark logged into the Wildbook database.
Researchers are using this information, as well as data obtained from satellite tracking of whale sharks, to unlock the mysteries of where these elusive animals go when they’re not hanging out close to shore.
After a long day of swimming with whale sharks at Ningaloo, we sit on the upper deck of the tour boat watching the bright orange sun dip into the Indian Ocean. I feel alive and incredibly lucky to have shared a brief moment in time with the biggest fish in the sea. I hope Stumpy keeps coming back to visit each year until he’s a very old, very wise whale shark. And by then perhaps we’ll be wiser, too.