Whale sharks - stars of the sea

Brad Norman from Ecocean, a research group based in Australia, tells us about his pioneering work tracking whale sharks in Australia's Ningaloo Reef and beyond, taking inspiration from the stars.

Like a whale-shark version of fingerprints, they have unique patterns of spots that can be mapped using star-spotting algorithms. Brad describes the tools Ecocean have developed to manipulate photographs taken at any angle allowing them to rapidly and reliably pin down the identity of whale sharks .

Sadly, you can make a lot of soup from a single whale shark fin so it's no surprise there's a giant price tag on their giant fins. But Brad and his colleagues have shown that whale sharks can be worth far more kept alive in the oceans since they return many times to the same site where tourists happily pay for the experience of swimming alongside them.

Ecocean promote a sustainable model for whale shark ecotourism, offering a win-win situation for people and sharks. 

If you're lucky enough to spot a whale shark in the wild, you can get involved by sending your photos to the Ecocean project.

Find out more

Ecocean

Arzoumanian, Holmberg and Norman et al (2005).
An astronomical pattern-matching algorithm for computer-aided identification of whale sharks Rhincodon typus. Journal of Applied Ecology.

Whale shark (Rhincodon typus) info at the
Florida Museum of Natural History

Whale Shark Project,
The Shark Trust

Brad - Yeah for sure. I'm glad you're equally as excite about whale sharks as I am. Because I've been working on them since about 1995 and they're a beautiful creature and one that's threatened so we needed to learn more about them.

So the initial studies that I undertook were trying to identify individuals and work out how many whale sharks are at Ningaloo Reef in Western Australia and if the same ones come back and if in fact they're moving other places because so little is known about them.

They've got spots on their skin. Along with many other animals sometimes you can identify the animals through these natural markings. So I proceeded to take tens, hundreds, thousands of photographs and worked out by eye which individual sharks were which and whether we got matches.

That became a little be onerous, a little bit problematic, when you get thousands of photos.

I was very fortunate to link up with a couple of colleagues, Jason Holmberg who's a software engineer, and a good friend of his who's now a good friend of mine, Zaven Arzoumanian, who's a NASA astrophysicist. Zaven works on identifying start patterns in the night sky using a particular algorithm.

We bounced around ideas and came up with idea that we might be able to use an adaptation of this algorithm that the Hubble space telescope scientists used to identify stars in the night sky, we might be able to adapt that to basically identify individual sharks. It's sort of like a bit of fingerprint technology, really. 

And it's worked brilliantly. We've got many, many whale sharks in the library and many we can prove are coming back to Ningaloo Reef and other parts of the world using  this system.

Helen - Presumably you have to be able to get around problems like if you've taken the photograph from, say, different angles, maybe in different light conditions and so on.

Brad - The software, the way the system works, basically it deals with the angles between triangles of spots in an area behind the gills. Now that's great if you're side on the animal at 90 degrees and those triangles, those hundreds of triangles that the programme will draw of the pattern of spots, that will work perfectly.

But when you're not at 90 degrees to the side of the animal and you're taking a photo from behind or in front or below or above those angles get a bit screwed because of your angle to the shark. 

So, with actually come up with, well, it's not me, but a gentleman called Seth Ladiger, who's another programmer. He's come up with a system where we use 3D modelling. We take a photograph, put that photograph on a virtual 3D model of a whale shark. We then move the whale shark to be at 90 degrees and then we unwrap the photograph again. And what will happen is the angles will be what they would have been if you took the photo at 90 degrees. So it allows us to actually use those photographs that might not normally have been able ot be used. And it's working really well.

Helen - Do we know if those patterns change during the lifetime of an individual whale shark or do they really stay the same from when they're quite young to when they're much older?

Brad - Bearing in mind that when the whale sharks are born, they're very small. They're only half a metre in length. They can get up to, believed to be up to 20 metres. So, this is the beauty of the triangle system that we use. Although the animal will grow, the angles between the triangles that are drawn between all these spots, they will move equally as well so we don't see any change in the angles between the spot patterns over a period of time.

Helen - Wonderful, and what sort of things are you finding out from these tracking studies? What are we learning about the lives of whale sharks?

Brad - This system is letting us monitor the number of whale sharks that are coming to different locations. We started at Ningaloo Reef in Western Australia, but the Ecocean library is now expanded to receive photographs of whale sharks in 45 different countries now. So it's actually giving us a global monitoring programme for these species.

The long term study that we started at Ningaloo has shown us that may of the same whale sharks are coming back every year which is a great sign. Lots of new ones as well, which is really positive because it is regarded as vulnerable to extinction, their number shave been declining dramatically over the years.

What we've done in Australia is show that ecotourism can be an economic as well as an ecologically sustainable alternative to the once only value of killing a whale shark for fins.

But it's very, very important that it's not just an open slather and hundreds of licenses or boats potentially interfering with their natural activities. There's some basic things - you don't touch a whale shark, you don't get in their way, you don't have too may people around the animal, and you keep boats well clear.

Helen - A really important part of the Ecocean project, it seems, is drafting in the help of members of the public. Anyone lucky enough to spot a whale shark in the wild and catch it on camera can send the photos into the Ecocean photo library. Have you got any tips for taking useful photographs?

Brad - The simple thing to know is preferably be side on to the animal. The area we're mainly using for photo identification is the area behind the gills just above the pectoral fin.

As a scientist, myself and my colleagues can only be in one place, one day of the year. But we can have, and we are getting thousands of ecotourists that are becoming our research assistants. Their input is a really major part of our global monitoring system and we really appreciate it.