Great white sharks
Great White Sharks Part 1
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UTS Science in Focus: Great White Sharks: Research for conservation of the world’s greatest predator
Duration: 54 minutes
Thanks for taking the time in your evenings to come and listen to my good friend Bill and myself. As you’re told, I’m actually originally from Sydney, so I know this area pretty well, but I’m in Hobart with CSIRO Marine and Atmospheric Research, and although I’m known for working on this particular species, I actually do other stuff as well. And this is, I must admit, this is some of the fun stuff that is probably one of the reasons I got into marine science in the first place, was to do fun stuff, and it’s great to be able to continue it.
Okay. White sharks. Great white sharks – we’re talking about the same thing. If you ever read that well-known scientific journal, The Sunday Telegraph …
[Laughter]
Actually, I should have asked another question – is there anybody from the media here tonight? No?
[Laughter]
Good. The Sunday Telegraph. Yep.
This is a very common shot that you’ll see in the media; I’m sure you’re probably familiar with it. These are real white sharks. This is what they can do. I’m reminded that if you tease a Labrador enough, it will bare its teeth and look really vicious as well. These shots have actually come from South Africa where sharks have leapt out of the water in response to towing a seal decoy around. So although we know white sharks can do this, they have much more complex behaviours than just this sort of circus activity that people put them through. Which brings me to another point – is where you get your information from, on white sharks. I’m sure if you’re like most people, you read newspapers, you see the news, you go on the internet if you’re interested, and you google ‘white shark’. And you will get all sorts of fun stuff. Some of the fun stuff that you’ll see is stuff like this. I’m not sure if anybody in the audience has seen this before – anybody seen this? Yep – a few people nodding. So you probably know a little bit about the history of this. This is a really fun article in that well known scientific journal, the Sun Herald. Certainly, some of my best work is published here.
[Laughter]
It’s sadly true, actually.
[Laughter]
So it says – and there’s multiple screens, which I’m not used to, so I’m going to have to duck around a bit, but look, it says it’s the picture that scared off a thousand tourists. And here we have a very big, scary shark and a very small, scared surfer. So you know, in that situation I think you’d be rightly scared, wouldn’t you? Interesting thing about this is that there is something wrong with this photo. There we go. Something wrong with the photo. What’s wrong with this photo is that the shark and the surfer were never in the same place at the same time. Hmmm. Alright. Point number one. Point number two – this is really exciting. The shark was really that big.
[Laughter]
Yep. Now look, I have to admit, the Sun Herald did admit that later on in the article, but the point is quite simple. This is Photoshop, and it’s very good Photoshop. The point is quite simple – there’s all sorts of information you can find on white sharks; however, not all of it is educating you. And the challenge is to work out what’s fact and what’s fiction. So tonight, with any luck, we’ll at least – I hope you go away tonight, at least, with more information about white sharks than you do now. We don’t know everything; there are still many pieces of the jigsaw puzzle missing, but I’m hoping that we can fill in a little bit for you tonight.
So, let’s get through a few interesting facts first. Firstly, white sharks get big. We know that. They get to at least 6 metres long, and that puts them in the weight category of 2000-3000 kilos, so there’s a lot of flake there. Really big sharks. We think that they live to 50-60 years; there’s some recent work out that suggests that they may even live for longer than that. Females don’t reproduce until they’re really big. In Australian waters, it’s close to 5 metres before a female white shark is reproductively mature. There’s a reason for that – that’s coming up. The really interesting part about them is that they’re not your average goldfish.
[Laughter]
You’ve probably picked that up .When was the last time that a goldfish attacked you? So things like, normal fish like snapper or whiting or flathead are pretty much the same temperature as the water around them. White sharks are really different. White sharks maintain their body temperature at 25-27 degrees. They’ve got physiology that’s more akin to mammals than to fish. They have really big babies. And this is why females have to be big before they reproduce. So a female white shark can produce sort of, we think around about at least 10 pups, we call them, babies, per pregnancy. When a white shark, when it’s born, it’s born a complete shark. They don’t lay eggs, so a complete free living shark will swim away. There is no parental care, and they’re 1.3-1.5 metres and up to 35 kilos at birth. Makes your eyes water, doesn’t it?
[Laughter]
Yes, only half the room laughing.
[Laughter]
They eat fish and other sharks and stingrays when they’re small, and when they get bigger they add things like marine mammals, like seals and the odd dolphin and things. One of the things that you’ll notice a lot in documentaries and in scientific literature on white sharks is their association with seals. And it’s almost as if all they do is hang around a seal colony – that’s not true. And in fact, white sharks spend less of their time, or only a small proportion of their time in any one year at a seal colony. Most of their lives are spent somewhere else, feeding on other stuff. The reason that you see that bias in the literature and in documentaries is that seal colonies are really nice places to go to film white sharks or to work on them. It’s not because they spend most of their time there. ]
So, most of our work revolves around understanding movements or behaviour. And where we’re focusing that work is to try and understand how many sharks there are out there are how their populations are tracking. We’ll come to that point a little bit later. However, to do that, it really helps if you have a pretty intimate knowledge of where they go and how they behave and what areas are important to them. So you can find areas where you can count them, for example. And you can understand how populations around Australia or around the world are linked. So the way we do that is really neat nowadays. Back when I started, we didn’t have the electronic tag toys that we have today. About 10 years ago, there was an upswing in technology for us and it really revolutionised how we study white sharks. They’re not easy animals to study, as you could probably imagine. We use a variety of different toys to understand the movement patterns of white sharks. The conventional tags up here, we’re not going to talking about those tonight – they’re like game fishing tags that you poke in a game fish and you release it. So we tag 500 sharks or so like that. 500 white sharks. Where it gets really interesting is the acoustic tags and the satellite tags – there’s about 300 of them that we’ve tagged. These are the toys of choice down here –this is what we call a pop-off [inaudible] tag. What this does is it collects information on the depth the shark is swimming, the temperature of the water around it, it collects information on light and it’s got an accurate time clock and you can actually calculate where the shark goes from some of that data. But the interesting thing about that tag is that we can program it to collect all that data. We can program it to collect all of that data, we can program it to sit on the back of a shark – it goes on the outside – and pre-program it to pop-off on a particular date and time, float to the surface and then transmit its data back to us by satellite. So there’s a lot of remote technology in that.
So that’s a really neat toy – we use a few of those .This one’s pretty much the same, but this is what we call an archival tag. It does the same job, but it doesn’t pop-off and we have to get that tag back to get the data. We don’t use too many of those because we don’t get too many back.
[Laughter]
Now this one here is a really neat one. This is just like the pop-off tag, collects the same data, but in this case, every time the shark comes to the surface and sticks its fin out of the water, the tag turns on its transmitter and transmits the shark’s location and the data that it has collected. And so we can use that to actively track the shark as we’re going along – so that’s nice. And this last little one that looks like a big black pill about the size of your finger is an acoustic tag. Those acoustic tags, they ping out a unique code to the tag that will identify an individual shark. We put them on the outside or the inside of the animal – they pulse their code out about every minute, and what they’re detected by is a series of acoustic listening stations of which there are hundreds around Australia , put in the water by many different researchers. We all collaborate and the data, as a shark swims past, what you get is the date and the time that the shark came within range, so you get information on when the shark arrived in the place, and how long it stayed there for and when it left, so that’s information that is really useful.
We’ll be talking primarily about these two tags tonight, and particularly about the satellite tracking tag, the one on the dorsal fin. I should point out that we have a great team of people that we rely on to do this, including – there’s one of those people in the room, Chris Gallan, I can see over there. I won’t put the laser light on you, Chris, but this is Chris here, and sometimes he has to stare down the animals in all good occupational health and safety aspects to get it to calm down. And he’s very good at that. Right. So, people always ask us, you know, how do you get the tags on a shark? Including our occupational health and safety people.
[Laughter]
And I always tell them, ‘It’s dead easy, really safe, don’t’ worry about it – stay clear of the pointy end.’
Now, this is going to be interesting – I need to start a video clip, so I might ask my friend up the back there to click somewhere in there. Here we go. Alright, that’d be great. So, I’m going to lean over the side and I’m going to poke one of those pop-off satellite tags into the shark. So here we go – oop, there it is. And there’s the tag. And I’m sure you all saw that, didn’t you?
[Laughter]
Do you want to see it again?
[Audience agrees]
Maestro, if you don’t mind. See if we can get that to work again. It might have to go all the way through. Yeah, thank you very much. This’ll be the last time you have to do things twice. So, you have to be really quick. I’ve got a tagging pole in my hand. I’m going to lean over the side of the boat, and I’m going to poke the tag in about – there it is, see? There it is. See, now the tag’s in. It’s as easy as that. So you can do this safely. We tag a lot of sharks that way, particularly big sharks, but some tags, it’s okay to put anywhere. But some tags you have to place more carefully, and the tags on the dorsal fin, of course, have to go on the dorsal fin – the satellite tracking tags – in a particular orientation, and you have to be a really good shot to do that. So what we do is we catch sharks to do that, and that sounds very exciting and it’s a bit more exciting than that, so what I’d like you to do – see that little black area up there? I’d like you to click on that please, if you don’t mind. So it’s that area up there. So you’ve got to click on the black – that’s it. Right. So we’ve caught white sharks up close to 4 metres, and of course you’ve got to get them to sit and be a good shark, not a bad shark.
[Laughter]
This one was good, this one was good. These are the old-style satellite tags that we used to use, before they started commercially producing nice little ones like this. We designed and built these ourselves, back in the 2000 period. But we kind of get a bit up close and personal with them and those [inaudible] some sharks. What happens when you tag sharks, right? Where do they go? And this is how we found out that they don’t’ live at seal colonies – we thought they lived at seal colonies, just like the Sun Herald told us. But, so, a lot of our tagging work is done down here in South Australia, Neptune Island. Has anybody done cage diving down there. Yeah? Great. Okay. Have you ever wondered where the sharks go when they leave the Neptune Islands? Well, I have. Let’s see. What I – again, I’m sorry, I need you to click on the screen to run that video clip. You’ll see coloured dots – these’ll be the satellite tracks of sharks tagged here at the Neptune Islands. Oh look, here goes one up to the Barrier Reef and over here at Port Stephens as well. But you see most of the sharks go west, and including up to Ningaloo Reef, where you dive with whale sharks I’m sure.
[Laughter]
And you have sharks going across the New Zealand. You get the picture – they move around a lot. My advice to you if you ever dive at Ningaloo Reef with whale sharks, make sure they have spots and a flat nose.
[Laughter]
It’s very important. But look, the point here is that white sharks move around quite, really long distances around Australia. The interesting point about the sharks that move – you saw a shark that went across the Tasman Sea to New Zealand? Interestingly enough, that was a 2 metre white shark – a really small juvenile. And in the process of doing so, it was diving to 1000 metres on a regular basis. Now we have no idea why they do that, but they do. And in fact we see this behaviour in white sharks of all sizes, but primarily the 3 metre plus ones, you’ll see in certain places, go out into deep water and do that. And in fact, in places like California and Mexico and South Africa, it’s quite common for white sharks to go out in the open ocean, and this, we never understood until we started doing this sort of tracking. How much, how important the open ocean was as a habitat for white sharks. They’re not always at the coast.
To illustrate that point, if you tag white sharks in New Zealand, you’ll see that they leave New Zealand and come to Australia – that’s fairly common.
[Laughter]
I’m not sure that’s politically correct, is it?
[Laughter]
They can go, they go up to that area, the Barrier Reef, down below the swains – remember where that other shark went to that we tracked? They also go to Norfolk Island, New Caledonia, Vanuatu; they’ve been to Fiji since as well. These sharks move around a lot, and you can see they cross broad areas of open ocean in doing so. In South Africa, there was a, this really neat paper some years ago, that documented a white shark swimming from South Africa over to Ningaloo Reef, and then it swam back again, by the way. And we have no idea why. So the open ocean is also an important habitat for white sharks.
However, I must admit, having said that, in Australia, most of the white sharks we’ve tracked have remained pretty close to the coast on the Continental Shelf, sometimes zipping down the Continental Slope to deeper depths. And a pattern has emerged when we’ve been tracking white sharks here in Australia. You’ll notice there’s two colours on this figure; I’ll give you guys a go over here now. So, the pink ones are sharks that we tagged in Eastern Australia. The green ones are sharks that we’ve tagged west of Bass Strait, and you probably see a bit of a pattern there. We’ve never seen a shark tagged on Eastern Australia that has crossed Bass Strait to the west. We’ve had one or two sharks from South Australian or Wester Australia go east, but they’ve generally gone back; well, one got caught in New Zealand, one went back. But most of the sharks that we tag in South Australia, for example, head west. And all the sharks that we tag in east Australia stay on the eastern Australian coast. It suggests that there might be two populations. In fact, when you look at the genetics, that’s exactly what you see. You see evidence of two populations of white sharks in Australian waters, separated by Bass Strait. Now this is actually not uncommon in fish fauna and invertebrate fauna around Australia; you often have different populations or sub species east and west of Bass Strait. So it’s probably related to previous sea level changes when Bass Strait was in fact a land bridge, but it’s remarkable that even though white sharks can travel broadly, that we can have these different populations in such close proximity to each other.
What I’m going to do for the rest of the talk now is concentrate in the east, on the eastern white shark population. And in particular, as you heard in the introduction to the talk, a lot of the work that we’ve been doing lately is based on juvenile white sharks. When we first started, there wasn’t a lot of information on juvenile while sharks because everybody worked on the big ones – the ones that you find around seal colonies, which are typically 3 metres and above. There’s very little information on where the babies hang out, and where the juveniles hang out. Well, we can tell you that in Eastern Australia, there are two nursery areas for white sharks. There’s one down here in South Eastern Victoria at the bottom end of 90 Mile Beach, but the other one is the one I’m going to talk about a little bit more, and that’s up here at Port Stephens, on the central NSW Coast, not too far north of here.
Now, I have to ask another question – this is your chance. How many people have been to Port Stephens? Mmmm. How many people have swum in the water at Port Stephens? Mmm. How many people have died at Flight Point? Yeah, good. What about places like Hawks Nest and Birubi Point? Yeah? You been there? Surf zones around there? Great. Okay.
[Laughter]
So a lot of the work that we’ve done is tagging juvenile white sharks up in this area, and you know, again, you probably want to know how we do that. In South Australia and Western Australia, where we tag much bigger sharks, we used to go to a place where they’re likely to hang out, and we put a mixture of tuna oil and minced up tuna in the water – burly chum – and we attract sharks that are already in the general vicinity to the boat so that we can tag them. We don’t do that for juvenile sharks. What we rely on is our mate Chris Callen over here to drive an inflatable boat into the surf zone to catch big sharks with sharp hooks. What could possibly go wrong?
[Laughter]
And this is exactly what we do. So first of all, we take an inflatable boat into the surf zone, because we figure that’d be a good place to go. We then – that was the new boat that we used; this is the previous boat that we’ve used. We then sneak up behind a white shark, so we spot them, we just cruise around the surf zone til we find one, and then we go ‘Ooh, look, there’s one’ and then we swing up to it, we throw it a baited line, we catch it, Chris encourages it to come into the stretcher, and be a good shark. My colleague Russ Bradford rolls it over and does a minor surgical procedure on its tummy, and we put the acoustic tag inside the shark, then suture it up, and then we roll it back over and we put the satellite tag on the dorsal fin. We give it a pat on the back and push it out; it swims away, and then it cruises around with all these tags on it. Couldn’t be simpler, could it? It’s good fun, but it’s actually a very controlled process. even with the big sharks, when we catch big sharks, we don’t fish blindly; we select the animal that we’re going to catch, we present it the bait, we do a pretty good job of hooking it on the left hand side so that when it’s in the stretcher, the left hand side is facing us so we don’t have to reach over the animal, and we go from there, and it’s in the stretcher for maybe five or 10 minutes. So it really is quite a controlled process – it’s not like your average fishing.
So, let’s see what happens. Now, I’m going to be a bit sneaky here; these are three areas of the coast. I’m going to talk about this one first, and then this one, and then this one. This is where the nursery area is, and what we’re going to see are the satellite tracks of sharks, which will give you an idea of what the activity of sharks in these areas are. So, first of all, let’s go along the section of the coast north of the nursery area, and the activity looks like that. So what you see are coloured dots; each colour is a shark, each dot is when the shark came to the surface and gave us a position for its whereabouts, and we’ve just drawn lines between them to give you an idea of the tracks. So you know, there’s a bit of activity up there, it’s kind of off the coast, which is pretty typical, and it’s not very exciting.
If you go south of the nursery area, south of Newcastle, it’s a bit more exciting. There’s a few more lines, but again, you notice the sharks are generally off the coast; they’re transiting in and out of the nursery area. So who are the people that swam up at Port Stephens? Uh huh. So what I’m going to show you now is the activity in the nursery area around Port Stephens. Port Stephens of course is this beautiful estuary here, and what I want you to look at are the beaches immediately to the south – Stockton Beach, Bennetts Beach here, and Mungo Brush. Now, I need my friend up the back to press the button here.
[Audience chatters, laughs]
Oh dear. So that’s pretty much condensed a three-month period from – well, it’s a bit more than that actually; I’m a biologist and not a mathematician, so I can’t tell, but it’s more than that – that [inaudible] is from October through to about February, so if you’ve ever swum, surfed or dived at Port Stephens between October and February, chances are, you’ve had company – and it looks a bit like that. Yep. Alright, so remember we’re talking about a nursery area. And what do people ask me all the time? ‘Is this where they breed?’ Because if this is where they breed, there must be some really big ones out here too, and they’re going to be a lot scarier than a baby one. So here’s a typical white shark in the surf zone. The answer to that is no, this is not where they breed. And the reason we know that is that if you have a look at the size frequency or the age structure of the white sharks we see up there, you’ll notice that we see a few five-year-olds and some four-year-olds and some three-year-olds and more two-year-olds and not many one-year-olds and we don’t see any little neonates, the younger [than a] year. So if this was a breeding area, and this was where the newborn pups go, you’d expect to see a lot down in that end of this scale, and you don’t see them. So those ones are somewhere else – this is primarily a nursery area for 2-5-year-olds. Occasionally we see some little ones, occasionally we see some bigger ones, but it’s generally that sort of size, age range, and that’s around about 1.8-2.6 metres in length. So they’re still reasonable size animals.
So if they’re not there, if the little ones aren’t there, where are they? And if the bigger ones aren’t there, where are they? So the way we get at that is to follow where they go when they leave, and this is an example of that. And excuse me my friend; I’ll need you to click again. What I’m going to show you is what is kind of a typical pattern for movement. Here’s a white shark up here; this is the satellite track of it, that’s Port Stephens and it runs from October through to January, and then suddenly it does something different. January’s coming. Christmas party – oh, here we go. And it does that. And guess where it went? Down to that other nursery area, which is kind of interesting. So that’s well and good. Now they don’t all do that perfectly; they go up as far up as Lady Ellis Island – you’ve probably dived there – or Herron Island – I’m sure you’ve dived there too. And they go as far south as Eastern Tasmania, but the general pattern is between those nursery areas. So what happens if you tag down at Corner Inlet? And again, if you don’t mind, this will be the yellow white shark. If you tag down at Corner Inlet or 90 Mile Beach, you’ll see this guy here, or this guy here, for you people. And I’m sorry about you guys over there.
[Laughter]
And I think it’s still moving isn’t it? Yep, there we go – and look what it does. Guess where it goes? Port Stephens. And this was a longer track – this one went for a year, and what happens when it gets sick of Port Stephens? It goes back again. So this is a really common pattern. What we have evidence for is that there are, in fact, big sharks down here. There are very small sharks down there too. What we believe is pupping occurs in Bass Strait, the pups first go to this nursery area where they hang around until they’re about a year old, on average – now there’s always exceptions. And then from here, they the move up the coast, they can go as far as the Barrier Reef, but they’ll end up primarily zoning in on the Port Stephens nursery area by the late winter/spring to summer, and then they’ll start this migration in between those two sites, until they’re about five years old. And then they do something else. So it’s really important – that migration, that regular migration between the sites, is really important to us, and I’ll tell you why in a little bit.
I’m just going to go back to that picture, because everybody likes that who swims at Port Stephens. Right. See those two arrows? They are surf clubs.
[Laughter]
If ever you wanted to position surf clubs in an interesting place, well, that’s it. This is the Birubi Point Surf Club, and this is the Hawks Nest. This is white shark city. The interesting thing about – an interesting statistic: the Hawks Nest patrolled area in the flags in front of the surf club, in the summer of 2010, was closed 44 times because white sharks swam between the flags. I kid you not. It’s absolutely true.
[Laughter]
So let’s move on. Let’s move on, because what people always ask me after saying things like that is that surely this is not normal. Is it normal for sharks to be in the surf zone close to the coast? Now, maybe I should – I’ll just go back one. I’ll just point out one interesting feature here: lots of activity along the beaches, right? But the nursery area footprint extends out 15 or so kilometres offshore, out to about the 60-120m depth contour. So it’s important to realise that the sharks aren’t always in the surf zone. They share their time with these sort of mid-shelf areas as well; they’re not always there. But that’s the nursery area, that’s the footprint in there. Right. So is it normal to see them in the surf zone? Ah, if you can have a look closely at this slide, you’ll see a whole bunch of fuzzy blobs. Those fuzzy blobs are sharks. These aren’t white sharks; they’re a whaler species, and this was taken, I think, around the Foster Tuncurry just north of the white shark nursery area, but this illustrates the point in that many shark species occur in the surf zone. There’s a fuzzy blob in the wave, obviously close to the beach. That is a white shark – that’s about a 2.5 metre white shark.
[Laughter, chatter]
Which one’s the nipper?
[Laughter]
Yeah, that speaks for itself. And this one speaks for itself too – this is one of the sharks that we’ve tagged. This was a month after we tagged it; it was filmed doing normal behaviour. I mean, this shark looks like it’s trying to grow legs, but this is normal. This is like the shoreline on Stockton Beach. This is not abnormal behaviour – this is absolutely, completely, 100% normal. Does it occur everywhere? Not as much as here, but yes, white sharks do occur in the surf.
In terms of how much time they spend at the beach, this is Hawks Nest Beach, or Bennetts Beach. This is Port Stephens here, Yacaaba Head, for those who know it, and this is the beach. What I’m going to show you is some acoustic tracking data from the acoustic receivers that we have set across the beach. Now, you’ll notice these coloured dots moving up and down the beach in a minute; the reason that they’re constrained to just out here is that’s where we had the listening stations that listen for them. The shark, each shark that you see, could have been right against the beach; they could have been out here, because that’s the listening station range, and we can’t pinpoint exactly where they were. However, if you don’t mind clicking the screen again please – this will give you an idea of what they’re doing at the beach. They’re swimming up and down a lot; having said that they swim up and down a lot, they don’t use the beach evenly. They spend most of their time down here where the surf club is. They go inside here to Flight Point in Halifax; they go out to the dive sites out here. Hmm. Yep, but you’ll notice that there are gaps where the disappear every so often – look, there’s one. And then they’ll come back. That illustrates that they’re not always at the beach, and my colleague, Bill Gladstone, will talk about that further, because we need to count them. We can only see them and detect them when they’re in the surf zone this way, and if they’re not all there at the same time, we obviously are not counting them all. And Bill’s going to go into how we resolve that problem.
So, do you know that white sharks are so common up here you can see them from space? Who has access to Google Earth? Go on Google Earth guys, and zoom in on the Hawks Nest Surf Club, because – I love this – because you will see fuzzy blobs, and they’re people. And if you look more closely, you’ll see another fuzzy blob further south, 150 metres further south, and if you zoom in you get a bigger fuzzy blob, but that’s a white shark on Google Earth. And so you can do that – it’s pretty neat.
Now I’m going to change tack a little bit, just to wake you up. We’re going to talk briefly about shark attacks. I don’t often like to talk about shark attacks in talks; I’d rather answer questions from you, but I’m going to pre-empt a few things. You’re probably familiar with the tragic circumstances and the events in WA in 2010/11; in particular, where over a period of time, five people were killed by white sharks. Pretty dramatic stuff. Gee, I wish we could stop shark attacks. I would like that no one ever should be bitten or have a family member bitten or die from a shark attack. It would be wonderful to do that. I’m afraid to tell you that that’s not possible. What happens when sharks and people meet? If you read the media, if you go the internet, it wouldn’t be surprising if you thought that every time a white shark and a person met, it would end in disaster for the person. That’s pretty much the message we get from the media. Alright. So what normally happens? What really happens when sharks and people meet? Let’s explore that little question for a bit. Alright – who can see the shark? Alright, yep – it’s [inaudible] where is it? I can see it – here it is. So for those with screens further away, that’s a white shark. These are people, and there are – trust me, there are people in the water. Look, there are people in the water. Okay – guess what happened? Nothing. Surfers – white shark. Nothing. Surfers – is that you Chris?
[Laughter]
White shark. Guess what happened? Nothing. Nothing. Nothing happened. If you go on YouTube, you will find many, many video clips of people and white sharks together, where nothing happens, okay? Right, remember those two surf clubs? Read the top line. There’s never been an attack at those beaches. Yet, white sharks and people come together every day up there during the right time of year. Now, you may say ‘well, that’s fine- they’re little ones.’ Well, white sharks of 1.8-3 metres, which is what we’re talking about up there, are responsible for 20% of all white shark attacks in Australia over the last two decades, so they can bite you. I’m not pretending that they aren’t harmless – these are not harmless puppies. If you’re in the water, and you see a shark, get out, is my … get out calmly. Don’t expect that you’re suddenly going to die or get bitten, but do get out. Respect these animals, if you can.
So. What do we know about shark attacks? Why don’t we, as scientists, know more about why sharks bite people? Because everybody asks us that question. There are many theories why sharks bite people; they’re only theories. We can go into theories later if you wish. The reason that we struggle to understand why sharks bite people is that firstly, nearly every attack occurs under a different set of circumstances. So in scientific terms, for every attack, we have an n – a number – equals 1. And you can’t form a pattern when you’ve only got one observation. It’s a fundamental problem in understanding shark attacks. This is a really interesting one – in nearly all cases, when sharks and people come together, nothing happens, and that’s because shark attack is the exception and not the rule. So we’re trying to understand the exceptions, and that’s why we struggle. People use, sometimes, the frequency of shark attacks to estimate the number of sharks. I’ll get onto that in a sec. However, the only time when the number of shark attacks is correlated with the number of sharks is when both are zero. Once you get above that, the relationship falls apart.
Recently, in Western Australia, it was claimed – or it was thought by a lot of people – because there was a spike in shark attacks in that period, five fatal attacks in an 11 month period or whatever it was, that white shark populations had suddenly exploded. What they were inferring was that you could use the number of shark attacks as a proxy for the number of sharks. Well, if we use the same proxy at Port Stephens, you’d have to come to the conclusion that there were no sharks up there. Clearly that is wrong. So the number of shark attacks is not a measure of either local shark abundance, or shark population size. It’s unrelated. Totally unrelated. And that’s why we have a lot of problems – if you think about the Western Australian population, there has been no white shark attacks for over a year. Does that mean the population has crashed? I don’t think so. I don’t think so. I’m not trying to belittle the tragic circumstances of shark attacks – please don’t get me wrong on that. Any form of accidental death or injury is a tragedy.
White shark attacks in Australia look a bit like that – this is total number of white shark attacks over time from 1990, and sure, there are more up this end. However, I have to admit, down this end, I’m not sure that we got the identity of all the shark attacks right. I’m pretty certain that some of the shark attacks we attributed to whaler sharks, for example, were in fact white sharks because they occurred in places that we didn’t really understand that white sharks should be, like surf zones and estuaries and things like that. So whether that shows a trend, I don’t – like I said, there’s a few more up this end, but gee, you’d be struggling l think.
The other thing that came out of the media reporting in WA recently was that Western Australia had become the white shark attack capital of the world. Ah, you probably saw that in the media. Look, again, there were some terrible tragic incidents over there. So what I did, I went to our shark attack database and I pulled out all the white shark attack records and plotted them by state – and here they are. Guess which one is Western Australia? You reckon it’s this one? Yeah, come on, you saw through my evil plot, didn’t you? Guess what guys? It’s you!
[Laughter]
And WA comes in third. However, of course, these are meaningless, because that doesn’t take into account how many people are in these states, and how many people are in the water, and all sorts of other complications, so, a statistic like this that is pure numbers really doesn’t tell us very much – so please remember that. Um, right. So, shark attack – has anybody ever bought a lotto ticket in the room? Come on, put your hands up. Yeah, a few – come on, you’ve all – surely you’ve all bought a lotto ticket. So, how many of you who’ve bought a lotto ticket have won first division?
[Laughter]
None? Has anybody bought more than one lotto ticket? Yeah? So even though you’ve never won, the chances of winning are so remote you’ll probably never win, [but] you still enter, right? Yeah, okay. Let’s think about that. So when you enter the ocean, it’s a bit like buying a lotto ticket. Every so often, the sharks win division one.
[Laughter]
However, you’ve got more chance of winning division one than they do. It’s a really rare event, compared to the number of times people enter the water around Australia. How many people entered the water today? Yep, and how many – let’s think of how many around Australia entered the water today. Tens of thousands? How many attacks were there today? None? Lotto. In fact, it’s even worse than lotto. I don’t know why the sharks bother.
[Laughter]
So, my point here is that we are blessed in Australia with healthy marine ecosystems, and we get a lot of marine ecosystems. I mean, you guys are here tonight, whether you think about it or not, because you value marine ecosystems and you value the healthy marine ecosystems. We get food from the sea – I’m sure a few of you had seafood. Guess where it comes from? The ocean. And we’re blessed with really well managed fisheries and good ecosystems and we harvest from the sea. We also go into the ocean for recreation, and we enjoy it enormously. We use it for sport. Sharks are a natural part of healthy marine ecosystems, and it’s because we have a healthy marine ecosystems that we have relatively healthy shark populations. Important stuff to remember.
Now, I’m just going to quickly run through a couple of things and I’ll let Bill take over. White sharks were protected in Australian waters in about 1996, 1998. What happened then was that the government set up a recovery plan which is a list of actions that you want to try and enact to – guess what – increase the population. So the objective of the plan is to see the populations recover; ie, we want to see more of them. And to measure the performance, we want to see the population increase. One of the most difficult things about trying to understand that is, at the moment, or prior to this, there’s been no easy way to count how many white sharks are there. They’re incredibly difficult to count, and [to] understand how that count relates to the populations size. If you can’t count how many there are, how on earth can you evaluate whether a recovery plan is having benefit or not having benefit? You can’t. So one of the really important objectives is to work out how to count them, and how the population’s going, and that’s what our research is focused on doing in the future. So how do we do this? One thing to remember, even though white sharks are protected, they still get caught. That doesn’t stop them from dying, [but] having said that, they get caught in commercial operations, by wreck fishers, commercial nets. People have even caught our tagged white sharks –look, here’s one of our tagged sharks up on a beach with a tag on its fin. That guy kindly put it back in the water for us, and it did swim off and it survived. They have valuable bits that people sell, which is now illegal in Australia. However, they still get caught.
Having said that, commercial fishers who catch white sharks do an incredible job, by and large, of releasing live sharks, so they should really be applauded for that. They really do a good job, by and large. So the sorts of things that we’re interested in doing here is working out how to monitor the population size, and what we’ve seen in some jurisdictions in Western Australia is that when people get really scared about what’s going on, and Twitter and Facebook and social media their thoughts, however rational or irrational they may be, people stand up and listen, and it can drive for reactive government policy, and that’s not the greatest way to handle government policy. I should be careful about commenting on WA. Anyway, that’s – we want to see, if you’re going to have policy, let’s make sure it’s well thought out and it’s based in science where it needs to be. By-catch management, sharks get caught accidentally, we want to try and minimise that, and there are ways we do that. This is an interesting one – of course we want to balance conservation with real or perceived public risk, and it’s hard to do that sometimes. My favourite one is coping with recovery success – if we’re successful, there’ll be more sharks. What does that mean, and what will people think about – what do you think about that? You want more white sharks out there? Yes we do, by the way. Will it mean that there are more interactions between white sharks and people? Probably. But remember, most of those interactions lead to nothing. Will it mean there are more attacks? Hard to tell, maybe one or two, who knows? But by and large, probably not. What we’re trying to do though, if we learn more about white sharks, maybe we can better educate ourselves to minimise our risks, as well as the risks we pose to them. Shark cage diving – we can talk about that later if you want to. And of course, understanding where the important areas are.
But how do we measure population size and trends? This is where we’re doing some really neat stuff, and this is where I’ll hand over to Bill, but so how do we estimate population size and trends? First of all, we need to understand a few things to build a really nice population model, to see how populations are going. Because we can count every one, we have to do some estimating. The way we do that, first what we want to do is we want to understand juvenile survival. How many babies survive to be bigger babies or adults, right? And because we know now that juvenile white sharks cycle between these two nursery areas on an annual basis for at least a little while in their lives, this is where the acoustic tracking comes in. So those acoustic tags, we have acoustic receivers in a nursery area at Port Stephens, in the nursery area at Corner Inlet down in South East Victoria and through our friends and colleagues in other institutions, there are hundreds of receivers up and down the east coast.
When we tag white sharks, we can detect them moving between the nursery areas, whether they reach a nursery area, whether they come back to Port Stephens each year. If they don’t come back t Port Stephens and we don’t hear them anywhere else, they’re probably dead. There might be other explanations, but they’re probably dead. And if we do that for long enough, tag enough sharks, we start to work out how many survive and how many don’t.
We’re still tracking sharks that we’ve put internal tags in in 2008, by the way. Not all of them, but some of them. So we build up a picture of juvenile survival that we can put in our model. We need to also estimate how many adults survive, and how often they reproduce. And this is something really hard to do. Now, we’re using a fairly new and nifty genetic technique to do this. What we know about white sharks, we think the gestation period in white sharks I about 18 months, so they can’t reproduce every year as far as we understand. We may have that wrong, but that’s our current thinking. What we can do with genetics is that we can type a juvenile – we take tissues from the juveniles every time we catch and tag them – we can type an individual juvenile for its mum and dad. So we can recognise its mum and dad from that tissue sample. What we can tell then, if we get a one-year-old shark and a two-year-old shark in the same year, and it shares the same mum, that tells us that that mum has produced babies, has reproduced on consecutive years, every year. And that would be the reproductive frequency. If we only see a signal where there’s a year gap, it’s every two years. If there’s a two-year gap, it’s every three years, so that’s the way we’ll get a reproductive frequency.
Estimating adult survival is also from that data too, in that if you get a one-year-old shark and a two-year-old shark that shared the same parent, that parent has survived those two years. And similarly, if you get a one-year-old and a five-year-old shark that shares the same parent, that parent has survived that period as well. Using that information with enough sharks, we can start getting a handle on adult survival as well. So it’s pretty neat.
Estimating adult abundance, again, can come from the same sort of genetics, because there’s a relationship – if you have a look at what we call sibling and half siblings, so a sibling is, sharks are siblings if they share the same parents, the same mum and dad. A half-sibling is that you share the same mum OR dad, and there’s a mathematical relationship that if you type all the juveniles and you look for how many full siblings and half filings you have, or no matches, there’s a relationship between that pattern and how many adults are in the population. So that’s another way of estimating adult population abundance. Where it really becomes nifty is – is nifty a scientific word? It used to be! So to ground truth such a model, it really helps if you’ve got an estimate of a number of sharks in a certain age group or set of age groups, and that’s where Bill comes in. Because what we can do in these nursery areas is estimate the numbers of juveniles and use some mathematics, which Bill will go through, to work out how many juveniles in those age classes are there. And that ground truths our population. You can also then backtrack to how many adults would have produced that many babies, because we use the survival rate of those young, knowing how old they are in here, which is really important. And then knowing how frequently the adults reproduce, and how many babies they reproduce – you can go backwards to work out how many newborn pups there would have been and how many adults would have needed to produce them. So you can do a lot of powerful stuff. You can bring all that data together, and you start getting a really good population model that we can start estimating numbers and, over time, estimate trends.
Of course, this is just for the Eastern Australian population for the moment, and that’s where we’re focusing our time. There’s a lot of questions about what white sharks are doing in the west. At the moment, we don’t know where the nursery areas are in the west, so we can’t do the same work. But this is the next step, after we work in the east – we’ll go to South Australia and Western Australia, and go to nursery areas and we’ll start this work over there, and repeat it. Because we don’t know where the nursery areas are, we’re doing some work in South Australia and Western Australia at the moment, which includes – juveniles do appear there; they sometimes get caught. We’re hopeful of putting satellite tracking tags on them, and they should lead us to where the nursery areas are. At the same time, we’ve found a place where we’re pretty sure we can – the large adult females we’re looking at are pregnant, and we’re putting those pop-off kival tags on those females. Female white sharks produce pups in Southern Australia in late spring to early summer, so we’re coming up to that now. So we’re tagging what we believe are pregnant females now with the hope that the tags will show us where they go to pup- so this is how we’ll find the nursery areas in the west, we hope, and we’re collaborating with our WA Fisheries colleagues on that. That’ll give us information on the western shark population; bring that all together and it’ll give us that integrated, national approach – and remember, this is collaborating with a lot of other people. So one of the really key things though is our ability to estimate somewhere along that line, the numbers of animals in the population, and this is the work that Bill will tell us about in the next part of this talk.
So thank you very much; I hope you learnt something tonight about white sharks from that work. So what I’m going to do now is hand over to my friend and colleague, Bill Gladstone, who’s going to tell you a bit about how you go about counting juveniles. Thank you.
[Applause]
19 September 2013 53:59
Great White Sharks Part 2
![](/sites/default/files/styles/video_thumb/public/video_thumbnails/GuTw4A2zXBk.jpg?itok=pg9BiENp)
UTS Science in Focus: Great White Sharks: Research for conservation of the world’s greatest predator
Duration: 32 minutes
My collaborator in this presentation tonight is research assistant Rob Carraro, and Rob was present on all the aerial surveys we’ve done over the past couple of years. I’m going to explain and expand upon a little bit more the relevance of understanding the numbers of juveniles to that big question that Barry posed at the end – about finally coming up with an answer about how many white sharks there out there in the ocean, on the east coast or the west coast, because without that understanding, we just don’t know whether the conservation actions that we’re implementing are working or not. So our goal is really to get a number. Doesn’t sound like much, but we just want to get a number to know, are the populations increasing? Are they stable? Or are they decreasing? Because we’re investing a lot of time and effort in conservation of white sharks.
I’ll start by showing you how this work links back to that jigsaw that Barry concluded with. I’ll explain how we do the aerial surveys and what the limitations are of the technique, I’ll show you some of the results we’ve got, and then I’ll conclude but putting all the bits and pieces of information together to come up with a number. So, here we go.
So firstly I’d like to acknowledge the large number of people who participate in these programs. Doing these field-based programs involves lots of logistics, and they’re very expensive. And so a lot of people do a lot of hard work to make them happen, and it’s a great pleasure to be able to acknowledge the work and the support of the people and the organisations involved in it.
So Barry, at the end, finished with the challenge of estimating the number of juvenile white sharks. And we know now from the work he has done is that a good place to start to find an answer to that is the area off Port Stephens, where Port Stephens is the centre, in that nursery area, because we know with some predictability that the juveniles will come there and that at some time they’ll be close to the shore where the water is shallow and it’s clear and we can see them. So they’re there for us to count, which is a prime requirement of coming up with a number about how many sharks there are. So we can really answer that first question about how many juveniles there are, because we know that they spend some time in the surf zone. So we can do that at this location, the nursery area. And we do that by helicopter – we fly above the surf zone, and I’ll explain the technique a bit more in a couple of slides, and with a fairly standard protocol and technique, we can observe them and record their behaviour and note down where they are and what they’re doing. The helicopter team, the survey team, consists of three of us: there’s an experienced pilot up the front there, there’s Rob sitting next to the door, and there’s me behind him. We take it in turns to see who’s the observer and who’s the recorder, because it’s a very busy time, hanging out of a helicopter, looking down, trying to count sharks and record what they’re doing. So we take it in turns to see who does the hanging out the door and who does the writing down.
Now in order to fully understand that question about how many juveniles there are, it’s actually a lot more complicated; there are a lot more questions than that we have to first answer, or answer along the way. And the first one is, if we know how may are in the surf zone, we also have to be honest with ourselves and say well, how many were there but we didn’t see them? Because the surf zone is a dynamic environment – there’s waves breaking, it’s not always ideal conditions, so there may be some sharks that we didn’t see. They were there, but we may not have seen them. So we need to have an answer to that question as well and a way of doing that.
We also have to know how many juveniles were in the nursery, but not in the surf zone. All the sharks are not in the surf zone always, at the same time. There are some in the surf zone, and there are some outside the surf zone where we’re not surveying. So we need to be able to understand, in addition to the numbers we count, how many are there but we didn’t count them. And finally we have to know, of all the juveniles on the east coast at that particular time we did the survey, how many were in the nursery area? Because that’s one of our goals, to say ‘how many juveniles are there on the east coast?’ We have to answer that question as well – so a series of one question embedded within another, and that’s something you could imagine that jigsaw puzzle of research questions that Barry concluded with – each of those small boxes that he had, has lots of these multiple questions embedded within it. And this is the sort of the thing that motivates Barry and I and the people we work with – this is amazing to try and work on these sorts of questions.
And I love this quote – this is one of my favourite conservation biologists, Bill Sutherland from Cambridge. And I think he really summed it up quite nicely, when you think about how complex it is to answer these questions. And it’s really – ecology’s not rocket science, and we’re doing ecology here to provide the answer – in fact, it’s much harder. Just think about it – if you want to land a couple of people safely on the moon, you stick them in a rocket, you press a button, you aim it in a general direction, and away it goes.
[Laughter]
And fundamentally, if you reduce what they’re doing, they’re really using three equations developed by Isaac Newtown several hundred years ago. Big deal.
[Laughter]
This is much more interesting, and I think challenging. I hope you’ll agree by the time I get to the end. I’d still love to go to the moon.
[Laughter]
So, this is how we do it, for the helicopter spotters in the audience, it’s a Robinson 44 that we fly in – a four seater. There’s Deb, the pilot. We track north from Newcastle along Stockton Beach, flying at a height of 500 feet, so for helicopter geeks, we still talk in imperial – fly 500 feet at a speed of 70 knots, which is approximately 130 kilometres per hour, travelling north at a distance slightly offshore as we travel north, just above where the waves are breaking, and looking down into the water to spot sharks. We get to the end of the beach at Birubi, we stop surveying here, continue north until we get to Yacaaba Headland, where we start the survey at Bennetts Beach at Hawks Nest, the small village of Hawks Nest. And we use the same protocol, the helicopter is just positioned just offshore, we’re heading north, looking westward down into the surf zone there, and continuing along the [inaudible] up to the next point, which is Little Gibber, just opposite Broughton Island, and then we continue further north along [inaudible] called Mungo Brush, until we get to Seal Rocks, one of the most beautiful places, I think, on the east coast. That’s an ideal day for doing aerial surveys, with very clear water, calm, very little wind, but surprisingly, we see very few, and we’ve actually seen none – juveniles there. This is just outside the nursery area, but they don’t go beyond that boundary. We’ve never seen them there, despite those beautiful conditions. So we do a nice U-turn and come back, and start the transect again, heading south. So we do a northward transect first, and then a southward. On the southward transect, we’re positioned slightly differently above the beach, looking down into the water, obliquely again, to give us a different perspective, because now the sun will be at a different angle, and we’ll get a slightly different perspective about what’s in the water. And you can see here, can anyone spot the shark that’s there?
[Audience murmurs]
There it is – somewhere around there. And we circle around the shark, with one of us keeping an eye on it and telling the pilot it’s at 8 o’clock, 9 o’clock, 7 o’clock so that she knows where to get us back on top of it, and we circle it, and as we circle it, we’re noting down information or our observations about how large we think it is, what its behaviour is, what direction it’s swimming, is it associated with any other species and is it doing anything unusual? So these are our, what we call our transects, one of each of the main beaches – along Stockton Beach, which is 31 kilometres, then Bennetts Beach, which is 13 kilometres, and then Mungo Brush, which is 32 kilometres. And then we do that, as I said, north and then south, and we only survey within windows of very specific conditions, to make sure that the data we’re collecting is not influenced by the weather, for example. So we try and maintain, as much as possible, standard conditions. We only survey between 8.30 and 12.30, so the observations are not influenced by reflections of the sun off the sea. We have a window of sea states, about the height of the waves, the wind etc, and it’s a bit like trying to make a decision about whether to sell shares on the stock market or not. There’s a lot of conversation and email that goes between the three of us about, can we go tomorrow, can we go next week? Looking at the weather – and if anyone’s a surfer here and trying to look at weather conditions and predict, it’s almost like Lotto as well – trying to win Lotto to get ideal conditions, but we do it. We spend a lot of time doing it and thinking about it and planning to minimise the error that will affect our estimates or our likelihood of seeing sharks.
So this is how we discriminate or identify a white shark from the air. We see other sharks – we see hammerheads, and it’s fairly easy to tell whether a shark is a hammerhead or not, but we also see grey nurse sharks and whaler sharks, and whaler sharks are very difficult to identify from the air. So these are the main features we use. They have a very pointy end. They’re fairly broad at the base of their pectoral fins, which are the fins sticking out tot h side, and they’re quite a distinctive shape, those pectoral fins, as they stick out from the side, and they also have a very distinctive keel at the base of their tail, where it seems to flare out a little bit, just at the base of their tail. And those features are fairly easy to distinguish from the air, particularly when they’re swimming and the conditions are good.
So we record quite a lot of information on the way. We note the position; we have GPS logs of all the sharks that we’ve seen, which note the position and the time when we see them. We estimate as best we can the total length of the shark, because that’s important in understanding the age of the sharks that are there. We note the behaviour, what they’re doing, how far they are from the beach. We also note other species we see, whether they’re associated with large schools of fish, and I’ll come back and talk about that in a minute. Any other sharks we see, or other species, within a fairly strict list of things, and we’re also noting down the environmental conditions – the sea state, the cloud cover, the air temperature, the wind speed and the water temperature. Now, as you can imagine, that’s a lot of stuff to record, so we have to be fairly restrictive with the amount of stuff we do actually record, because otherwise you get information overload when you’re trying to write down stuff and look for sharks at the same time.
So these are the sort of things we typically see when there are sharks there, swimming close to the coast, close to where the waves are breaking, in very shallow water. These are good conditions, as you can see in the area where the waves are breaking where we all love to swim, it’s there, nice and clear, it’s easy to see them. And these are ideal conditions. It’s calm, there’s very little wind, the swell is small, generally higher tide is a better time, we find, because the sharks tend to come a bit closer to the shore when the tide is high, and that’s a typical way we might see a juvenile white shark swimming very close to the shoreline – and you can see the sand there, how close it is. However, sometimes they’re not ideal, and they do change – from the time we arrive to get on the helicopter and take off, the conditions can change, even with the best predictions they’ll change and it will turn out to be like this rather than the day before when it was perfect – when you have wind that suddenly picks up. And the other thing that affects us, particularly up there, is phytoplankton blooms. These blooms of single cell plants that will bloom over a period of a couple of days and we can’t predict whether they’re going to be there or not. It may be related to the change of temperature in the water, a sudden upwelling in the water, a change in the nutrient conditions, or changes in the animals that eat them, which might affect them.
Now, we’ve spent quite a bit of time, Barry and I, discussing this and trying to work out what species it is, and what name it is, and we decided that it’s one species that we know and love called snot.
[Laughter]
We think it’s the best scientific term, it’s a term we’re very familiar with, and that’s the best descriptor for the conditions up there – it’s very snotty. But it does play havoc with trying to identify sharks. Can you see the shark there? You can imagine, if it was, and this is what it was like one second later – okay? When the wave rolled over the top of it, the shark was still there; you can just barely, I think if you squint you can barely see the shadow of it just below the crest of the wave. The rest of the dark hue is the dead phytoplankton that’s sunk to the bottom. So this is where it becomes really tricky about observing the sharks; it’s affected by the glare, or on overcast days, the conditions aren’t so good for spotting.
However, when the days are good, we also get to see lots of other animals that are there – such as these minke whales. We see hundreds of dolphins – literally hundreds of dolphins – on a transect, and these are either part of the population that live within Port Stephens and are the basis of a very profitable tourist industry, or they’re part of a much larger population. Marlin – I don’t know how many people go fishing for marlin, or dive and see them, but I’ve only see on sailfish, one billfish, in my whole time diving. And to see these things from the air like this and alive, and not at the end of a fishing line or strung up at the end of a game fishing competition, is an amazing thing to see them. And I don’t know if the people at the back can see it, but this is a large school of tuna, and the little dots there are the tuna. To me, the really interesting thing is that here they’re swimming along as you might imagine a school of tuna does swim along – there’s the herd of them swimming through. But on some days, their behaviour changes to something we’ve never seen before, when they’re swimming in a line – what looks like a coordinated line – and it reminds me of those times you see birds sitting on a power line, being aggressive to each other and maintaining the same distance. Now it’s beyond my comprehension of fish sensory abilities, how they can do that to maintain a fairly uniform distance, but it’s an amazing behaviour we hadn’t’ seen before. We see lots of stingrays – this is an eagle ray in the shallows. And sometimes they form these huge schools, so we don’t know why, what’s going on – it may be related to a breeding phenomenon. So the other thing that we’re learning from these aerial surveys is they’re giving us an insight into these other amazing animals that share the nursery area with the white sharks, and the thing that I’m constantly amazed with is, we know a lot more about the limpets and the periwinkles on our rocky shores than we do about the animals on our beaches. And these beaches are iconic in Australia. They have a huge economic value, they have a huge cultural symbolism for us, but we know very little about the animals and their ecology on our beaches.
We’re starting to learn a bit more now about white sharks. So, here’s the information. Now, I’m constantly amazed when we go out there and we’ve spent tens of thousands of dollars, hundreds of hours, and we can distil it all into one graph.
[Laughter]
As a scientist, I love graphs. The clearer they are, you think wow, that’s a piece of art – I see exactly what this means; this is fantastic! But we spent all that time when we can render it down to one graph like that. I love it. So, what can we see? Firstly, it shows the number of juveniles we saw over a 12-month period – that’s for the most recent surveys from 2012 last year to this year. And the letters on the bottom are the months of the year, so we began the survey in July last year, and concluded it in June this year, and we’re going to start again next week, and it shows the number of sharks we counted going north, and the number we counted coming south – and I’ve separated them because there is a chance we’ll double count the same sharks. And as you can see, there’s a couple of conclusions you can reach from that. Firstly, the white sharks are there all the time – so it’s not a seasonal thing – they’re there all the time. Secondly, there’s a major peak in abundance in November. And the thing that’s surprising to us about it is how rapidly it goes up – you can see almost over the period of 7-10 days, there’s a huge jump in the number of juveniles that are there. Btu then it goes down again – it drops almost as quickly. The decrease probably doesn’t go right down, you can see it almost went to zero, but I think partly the conditions were very bad on that survey. It was definitely on the way down anyway, but may not have gone down as far as that.
What we’re going to try and work out with this next series of surveys, we’re going to try and refine that peak even further by doing more frequent surveys around that peak time. So we surveyed monthly for a couple of months, then we surveyed fortnightly – now we’re going to survey een more frequently around the time of that peak. Because of the nature of how quickly it went up and how quickly it went down, it may have even gone further up if we’d surveyed a couple of days before or a couple of days after. And as I’ll show you a couple of days later, understanding the height of that peak is really important for working out the total number of sharks that may be there.
Now, if we just look at one of those beaches, and this is Mungo Brush, the most northern beach on our transect, the pattern was the same. So here, as scientists we like to pull things apart and say ‘if we pull it apart, does the pattern still look the same?’ And in this case, it does, so the sharks are behaving in a similar way at the different beaches, and we do the same for those two other beaches and the pattern is the same. So they’re behaving in the same way at the other beaches, and this is the previous surveys we did from 2010 to 2011; we didn’t have as much money then so we didn’t do as many surveys, but the pattern was still the same – we still got that great big spike around November. As you can see there, it seems to decline more slowly, but the reason for that is the conditions were dreadful for eight weeks from November through to January. We had constant high winds, southerlies, large amounts of rain and storms, so it just wasn’t feasible to go out there. So it seems to decline very slowly, but that was because we didn’t survey for eight weeks.
Now one of the things we are interested in is trying to understand why – why the sharks are there, or why they change through time. And I mentioned before about the number of other things that we count, and one of them is the schools of fish, and as you can see there, it’s very easy to count and observe these large schools of fish. This is a school of Australian salmon, and we’ve often seen the white sharks in association with them, and here’s one – it’s a juvenile just going into the school. We often see them swimming around them and charging through and feeding on them. And here we are observing a similar school to that from the helicopter, and there’s a shark that has just swum into the centre of that school, and you can see the other sharks – there’s two other sharks hanging around the outside of it; one down over there, one there and one there. So there’s two other sharks, and the most we’ve ever seen is nine sharks circling around a school of salmon. So we think there’s some relationship with salmon and sharks, and again this is one of those other graphs –as a major science geek, these are some of the things I love to look at and think about, where we relate the number of schools of salmon in the nursery area on the bottom there, and that’s increasing from left to right, and going up is the number of white sharks we saw. So as the number of salmon schools are increasing, the number of sharks are increasing. The relationships are not perfect; as you see, there’s a lot of scatter around that line, but it’s a pretty good relationship. There may be other things that are driving the change in abundance in white sharks, but this may be one of them.
This is the positions of all the white sharks we observed in the recent survey. As I said, we have a GPS position for every one of them. This is where it was – the previous one. Here’s Barry’s map of the satellite-tracked sharks. And here again, this is a really good piece of results, because what it shows is us the sharks that were tagged with the satellite trackers, and the sharks that we’re observing from the air, are behaving in the same way. So the two independent pieces of information, independent pieces of evidence, reinforce the conclusion that the nursery area extends over that stretch of coastline from just north of Newcastle to just south of Seal Rocks. However, they move around within that nursery area from year to year. They don’t use the beaches consistently in the same way from year to year. And this is a finding that Barry picked up as well in the satellite tracking in the movement of the sharks that were tagged. In 2010 and 11, most sharks were at Stockton. In 2012 and 13, most of them were either at Hawks Nest or further north at Mungo Brush. So there’s still a nursery area, but for some reason they’re moving around within that nursing area in a different way in those different years, and we don’t know why and what’s driving it.
Okay. Let’s come back now to those questions. We’ve now got an answer to the very first one, about how many juveniles there are in the surf zone. We’ve got an answer for that, for each of those times we did the surveys from the minimum up to the maximum. Now let’s start thinking about those other things we have to think about – of the sharks that we saw in the surf zone, how many did we not see? Of the sharks that were in the surf zone, what percentage do they represent of sharks in the total nursery area? And the way we can get an answer about this is with those listening stations that Barry mentioned. The orange squares there show the locations of these listening stations, and that’s what one of them looks like with a diver deploying it. It shows the locations of those listening stations along Bennetts Beach near Hawks Nest. So the array extends along the length of the beach, the sharks are individually tagged so when the shark comes within the range of the receiver, it’s logged, so there’s a log there of the identity of the shark, and the time when it came within the range of the receiver. And it turns out that sharks, the juveniles, spend only about 20% of their time in the surf zone. That’s the behaviour we’re focusing on, but it’s not really the dominant place where they spend most of their time. Some spend less; that’s an average. Some spend less, some spend a lot more, but on average, 20% of their time is spent in the surf zone. So of the ones we’ve seen, we know there must be a lot more, because a lot of them are outside the surf zone as we were flying over the top of it.
Now the second missing piece of this jigsaw puzzle was, how many did we not see? And this map here shows the positions of sharks that were tagged with Barry’s acoustic tags, shown by the coloured triangles there, and overlaid next to it re the positions of the sharks we saw from the helicopter. And where the two of them line up very close together, we can be pretty certain it was a tagged shark that we observed from the helicopter, and we know that that tagged shark was there, because it was detected on the listening station. As you’ll see, there was a shark that wasn’t tagged, and that’s the yellow triangle; it doesn’t have another one next to it. That was obviously one we saw but it wasn’t a tagged shark. But there’s one way down in the corner there which was a tagged shark; it was picked up in the acoustic listening stations but we didn’t see it. This was the same time we were flying northwards at the time, and we didn’t see it. Same conditions, same time but we didn’t see it. When we put all that together, it turns out that the [ability to view] sharks by us is around 71%. Now, as a scientist – this is one of the reasons I love science – this is great. It’s great to be told that we’re wrong, but you’re wrong by this amount.
[Laughter]
Which other profession would say ‘tell me I’m wrong, and tell me how much I’m wrong’ and then say ‘thank you very much!’ because that’s really important, because if we know that’s consistent, then we can factor that into any further work we do – is say ‘well, you estimated 70% of the sharks, we know there must be a few more and we missed them.’ That’s great. It turns out that that’s a mean as well – that’s an average. Sometimes we saw 100%, and sometimes we saw less than that. And the reasons that we may not have seen them were the conditions. You know, it may have been a shark, at the time we flew over it, the shark may have been under one of those big mats of snot and we didn’t see it, or a wave might have gone over, or there was glare, sun glare. Nothing to do with us; we’re perfect observers, of course. It’s just the environment was factored against us.
[Laughter]
Now, what we can do – we can use the information about the number of sharks that were there, whether they were – and those that were outside the surf zone, but still in the nursery area, and the number that we didn’t see that were there, and we can now correct the numbers that we got on the aerial surveys to come up with a corrected estimate. And this is what it shows. So remember those graphs I showed with the big peak – the numbers there now are the corrected numbers of the juveniles in the nursery area. Not just the ones in the surf zone, but in the nursery area, taking into account those errors and [our ability to view them]. And it turns out at peak time, there may have been up to 250 juveniles in the nursery area. So this is now a really powerful number, because we’re getting much closer to being able to say, talk about total numbers of juveniles, and reaching that Holy Grail that Barry was talking about – about the east coast population estimate.
And with that, I’d like to finish and remind you, or at least alert you to some activities that UTS is supporting about raising funds for great white shark research, and I’d like to say thank you very much, on behalf of the survey team and myself. Thank you very much.
[Applause]
19 September 2013 32:23
Tags: environmental science, marine biology, great white sharks, Australia coastline, marine preservation
Great white sharks: Research for conservation of the world’s greatest predator
Despite being attributed with fatal attacks, Australians have a relationship with great white sharks that is a mix of awe, respect and fear. In previous decades, trophy fishing, hunting, and accidental captures in nets and longlines began a precipitous decline in the numbers of great white sharks in Australian waters, which led to their eventual protection. Being an elusive, roaming and largely solitary animal, it is difficult to determine the actual numbers of great white sharks.
In this talk, UTS Professor William Gladstone and Barry Bruce from the CSIRO will discuss their innovative and exciting research, revealing the complex behaviour and ecology of the first few years of the life of great white sharks, including places that are important to them. Recovery of the great white shark population depends on the survival of these juveniles.
UTS Science in Focus is a free public lecture series showcasing the latest research from prominent UTS scientists and researchers.
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