Swimming with whale sharks
Now it’s time to dive beneath the waves to meet one of the largest animals on Earth. Imagine being in the water alongside a fish the size of a bus and weighing about 10-20 tonnes. Well that’s the experience I had last month when I went to the Ningaloo Reef world heritage site. It’s located off the northwestern coast of Australia and as well as being the country’s largest fringing coral reef - meaning it lies close to the shore - it’s also home to the whale shark. Chris went out on one of the boats run by a local dive company that specialises in taking people “swimming with the big boys”...
Frank - My name is Frank Gaggliardi. My home is here on the Ningaloo Reef and take people swimming with whale sharks. So we’re standing on a fly bridge. So the top part of a 65-foot vessel that’s fully equipped for dive and snorkel operations and we’re currently looking at the 5th day and very lovely customers having a swim on a patch of coral bommies.
Chris - Just another day at the office.
Frank - Yeah, just another day at the office – very, very lucky. Very lucky indeed.
Chris - It is a wonderful place to work. How do you actually do what you do because people are paying your company to find them whale sharks to swim with, but how do you do that?
Frank - We keep it as simple as possible. So we have a charter company, plane company that is in town and we hire our own plane or charter our own plane every day that searches the back of the reef for whale sharks. It’s just one guy in the aircraft and he can get a bit dizzy circling around all day and he’s looking out of the side of the aircraft and he’ll spot them, and then he gives us a bearing so basically just a very rough idea. It’s in your say, 12 o’clock or your 1 o’clock, by about 500 metres to a mile. Once we get close enough to the whale shark then I’ll usually pick him up by sight from the boat and then we can look and stick into our guidelines how he act and drive around the whale shark to disturb them as least as possible.
Brad - I'm Dr. Brad Norman. I'm from a not for profit group called Ecocean, works on whale sharks in Australia and does some work overseas. Whale sharks are a fantastic creature. They're the biggest fish in the sea. They can get up to 18 metres in length but they are a gentle giant. They're a filter feeder. A huge animal, but we get to see them in a natural environment. To see this huge creature that’s of no danger to us, covered in a beautiful pattern of spots that we can get within a few metres while swimming alongside them is truly an amazing experience.
Chris - It is a beautiful pattern they have. Just describe that because I don’t think I can do it justice.
Brad - Yeah, it is beautiful. A shark’s skin is quite a dark colour, sort of a brownie, gluey colour, grey even, but all across the animal is white spots. Some of them are quite small but some of them are the size of a tennis ball. But those spots are sitting in a pattern that’s unique to each individuals, actually like a fingerprint.
Chris - And you can use that to identify them, don’t you?
Brad - Yeah, we do and that’s something that we sort of initiated up here in Ningaloo Reef and now, it’s a global programme where we can actually identify individual animals through the spot pattern and determine whether that same individual is returning on a daily or weekly, monthly basis, or in years to come, or if there's a lot of new individuals coming to Ningaloo Reef every year.
Chris - Do they migrate – these fish – or do you have a population of whale sharks here in this patch Australian coastline that stay here all the time?
Brad - We’ve been able to identify a lot of individual whale sharks from Ningaloo Reef and in fact, some of them have been seen or I photographed them over a 22-year period. So they’ve come back every year or almost every year for that period of time. now it’s a couple of sharks, but there's many sharks that we see on a regular basis, even yearly basis. But there's a lot of new ones that come through and there's a lot of ones that we don’t get to see again. So there's a transient and a resident group of sharks that come to Ningaloo.
Chris - So what is their range globally then?
Brad - Well, they are broadly distributed right around the globe, about 20 to 30 degrees north and 30 degrees south latitude, a sort of in that warm water tropical band, but the sharks are distributed all around the globe. But it’s only been in recent years that hot spots are being found in various parts of the world.
Chris - Is it a coincidence that some of the biggest animals on Earth are the ones that eat the smallest things because you said they're filter feeders? They're filtering out – in some cases – microscopic things to eat.
Brad - Pretty much. They can filter down to literally any couple of millimetres in length in these animals. They’ve got a lot of protein inside these small (33:34) cover part of krill or small crustaceans. They can feed on small fish and larger animals, but they seem to be able to find and target and survive by feeding with the smallest organisms.
Chris - What's the actual practicality of that filter feeding? How do they do it?
Brad - Well basically, there's two ways of doing it. We’re working what we can see. So a lot of the time, the plankton, the zoo plankton comes to the surface an evening and concentrate. The whale sharks actually target those concentrations. So they actually swim through, just swim like a normal shark through these patches. In fact, with their mouth agape and it’s called basically ram filter feeding through the top of the water column. It comes through, it gets filtered through the filter pads in their mouth, and then the water goes back out through the gills, and they take in all that food. That’s one way. There's another way that whale sharks feed and I just got back from the Maldives where they’ve been feeding in this manner where they sit very cool in the water and there might be concentrations of prey at the surface, and they basically suck water in. they suck that water in, they filter it out, and they go in their merry way.
Chris - When you say they filter it out, how do they do that?
Brad - Well, they’ve got filter pads inside their beautiful cavity and basically, it’s just a cross flow filtration across those pads that seems to pull out the small organisms and they can feed them.
Chris - How do they know when they got a mouth-full then?
Brad - Well, we need to ask one of them, don’t we? There's a lot of neat stuff we need to find out about whale sharks. I've been studying them for a long time, but just as an example, there is still not very much known about whale sharks. I think up until the mid-1980s – I got involved soon after that – there had only been 320 confirmed sightings of whale sharks globally. Given that these animals have been around for millions of years virtually, it’s pretty amazing. They were only first discovered by science in 1828. So, even though they’ve been around for a long, long time, they're quite cryptic, and they tend to stay away from places through history where we’ve been, and they really haven't been a commercial resource until the ‘80s though (35:56) fishing came in for whale sharks. So, there wasn’t a lot known about them. There's still a lot we need to know about them but they seem exciting species because given that they're the biggest fish in the sea, we know so little about them but we’re starting to find out new stuff all the time. it’s really, really important for science but hopefully, it’s going to be really important for the conservation of the biggest fish in the sea.