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Decoding mysteries of Ningaloo whale sharks
Rob Harcourt / Rob Harcourt Decoding mysteries of Ningaloo whale sharks

They are enough to scare the budgie-smugglers off the average punter snorkelling at Ningaloo Reef but fear not, the only way you'd be eaten by a whale shark is if you floated inadvertently through its massive mouth.

Each year tourists pay big money to swim with these ocean beasts, the biggest of any shark roaming the deep blue but very little is known about what many have labelled the most mysterious of the ocean dwellers.

But spending six weeks off the WA coast each year from May with the significant local population of whale sharks has enabled marine scientist Mark Meekan to start to crack their once-impenetrable code.

The Australian Institute of Marine Science researcher has spent 10 years studying and tagging the animals and in the ABC documentary Whale Shark, screening Sunday night, and viewers will relish his work.

A documentary team spent part of last year with Dr Meekan at Ningaloo, and followed him on trips to Christmas Island and the Seychelles.

The team captured the highs and lows of Dr Meekan and his team as they tagged and logged the paths of Ningaloo whale sharks that dart in all directions across the Indian Ocean and north to Indonesia and Timor.

With cameras metres from Dr Meekan, recording his delicate strategy as he attaches tags to the fins of the whale sharks, it's an extraordinary, first-hand look at how placid and yet potentially dangerous these animals can be. The documentary reveals the frustrations at such a precise procedure, where a split-second missed opportunity can ruin a day's work as a whale shark disappears out of sight.

Gliding through the water with an unassuming elegance, there is little doubt why visitors to Ningaloo claim swimming with the beasts is akin to a religious awakening.

With significant populations off Mozambique, the Seychelles, Kenya and the Maldives, the WA-based whale shark project is establishing links with other researchers around the globe in a combined conservation effort.

When Dr Meekan travelled to Seychelles, his 1000-strong database of Ningaloo whale sharks, identified through photographs by unique, fingerprint-like markings near their gills, was compared to the local database. The long-thought theory that some of the Ningaloo whale sharks travelled across the Indian Ocean to Africa remained unproved - there were no matches.

This was a positive sign for local conservation because fewer nations would need to be involved in the protection of the Ningaloo population.

Dr Meekan told _The West Australian _that since he began tagging, new technology had enabled a much clearer picture of where the whale sharks were heading, and for the first time cameras were being attached to them. The fresh research has also shown whale sharks are often victims of "boat strikes".

"We think some of our tags have revealed sharks being struck and killed by ships," he said.

"About 25 per cent at Ningaloo bear the scars of boat strikes. Some of these strikes are clearly big oceangoing vessels because the scars are huge."

In recent years, whale shark numbers have reportedly declined 40 per cent at Ningaloo.

The documentary sheds light on the current state of the area's whale sharks with revelations it is a predominantly young male population that has dropped in average size by nearly 3m over the past decade.

Cameras worth $40,000 attached to the sharks have shown they travel to depths of 1.5km below the surface.

Dr Meekan described the behaviour as strange: "It's dark, very cold, it's an inhospitable place. We have no idea what a whale shark is doing down there."

One camera showed a shark "standing" on its tail and sinking down from the surface. "You take one step forward and another 30 questions pop up," he said.

Whale Shark airs Sunday at 7.30pm on ABC1.