ABU DHABI // A frequent visitor to the waters of the Arabian Gulf, the world's largest fish grows up to 20 metres in length and boasts a unique spot pattern, similar to a human fingerprint. But much remains a mystery, with a team of researchers keen to discover much more, Vesela Todorova reports
Keith Wilson has seen so many whale sharks he has forgotten exactly how many. But each sighting is still a thrill.
"It is a special moment," he says. "You tend to forget all the diving rules."
The world's largest fish, whale sharks can grow to 20 metres in length. Even juveniles - the most commonly sighted in UAE waters - measure between two to eight metres, and are a sight to behold.
Mr Wilson recalled a time off Musandam when a whale shark was spotted from the boat he was on. Everyone on board, including the captain, jumped into the water to get a closer look.
As the marine programme director at the Emirates Marine Environmental Group, he clocks up many hours of diving.
Divers and snorkellers are most likely to see a whale shark, but sometimes the fish come so close to shore that they can be seen by just about anyone.
They are spotted in Dubai Marina about every other year. In Abu Dhabi, one visited the bay of the Emirates Palace hotel in October 2009.
It is easy to admire the sharks for their size and colour - they are grey with white spots - but that is not the extent of their appeal. They have the thickest skin of any animal, up to 14 centimetres, according to David Robinson, who is researching whale shark populations in the Arabian Gulf and the Gulf of Oman.
The fish are ovoviviparous, their young developing from eggs that hatch inside the mother, which later gives birth to them.
"A lot of people are not aware of just how remarkable this fish is," says Jonathan Ali Khan, a Dubai-based filmmaker who has been working on a project about the sharks.
They can live up to 130 years. That, he says, "explains a bit about their behaviour and approach ... they never seem to be in much of a rush unless bothered by irritating divers".
Mostly the creatures are seen at the surface to feed. When food is abundant, it is common to see aggregations of up to 200 whale sharks at once.
In the Gulf of Aden, near Djibouti, they congregate when arrow worms, tiny marine animals, are numerous. In Belize, in Central America, their arrival coincides with the spawning of parrot fish, which release millions of nutritious eggs. "These sharks have learnt to show up at certain times of year at certain locations," says Mr Khan. "They seem to be aware of a very complex underwater system."
Yet much about the giant fish remains a mystery. One question is where they give birth. Mr Khan believes the Gulf could be a nursing ground, given the large number of juveniles seen in the region.
"We are obviously close to an area that has been used as a pupping site," he says.
"It is possible that the northern population of whale sharks, as they grow older, start to distribute around the rest of the Indian Ocean."
Mr Robinson hopes his study, due to run until 2015, will shed more light on the shark's biology, the demography of the local population, and its migration patterns.
"There is a lot of speculation about whale sharks in this region but the truth is that nobody knows as no studies have ever been conducted," he says. "There is a large gap in our knowledge of whale shark biology and nobody knows if they even have mating grounds or if they mate opportunistically.
"Whale sharks are known to travel several thousand kilometres, but why they do this is not fully understood yet."
Mr Robinson is studying a large whale shark aggregation off the shores of Qatar.
He is also using satellite tags to follow some of the fish, and maintains a database of encounters - more than 350 of which have been logged since June 2010.
"Part of my research is based around a public data collection initiative, in which I ask divers to send me images of whale sharks they encounter," he says.
"This helps me to investigate occurrence of the species and, also, if the photo is taken in the correct area, to identify the individual shark."
Each whale shark has an area behind the gills, above the pectoral fin on either side which bears a unique spot pattern, like a human fingerprint.
Mr Robinson is asking divers who encounter whale sharks to send pictures or report the sighting to www.sharkwatcharabia.com or post images to the Sharkwatch Arabia Facebook page.