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NARRATOR:
In a remote corner of Australia…
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FISHERMAN:
Oh no!
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NARRATOR: …a group of bull sharks
is targeting sports fishermen
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with unprecedented ferocity.
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FISHERMAN:
Holy ****!
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NARRATOR: Showing evidence of
a sophisticated new hunting behavior.
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-You need to hook 10-15 fish…
-FISHERMAN: Oh, look out!
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…just to get one to the boat.
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NARRATOR: Now, a research team
is launching an ambitious investigation
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using ground-breaking technology…
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COLIN:
Oh, he's got it! How good was that?
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NARRATOR: …to find out if one of the
world's most dangerous sharks…
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FISHERMAN: Oh, there it is!
Ah! Look at the size of it!
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NARRATOR:
… just got smarter.
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Weipa, a remote mining town located
on the edge of northeastern Australia.
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Each year,
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hundreds of sports fishermen are drawn to
its shores by seasonal fish migrations.
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But more and more,
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their catch is being stolen
in audacious underwater raids.
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Some fishermen even claim
the sharks have learned
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how to recognize
and follow individual boats.
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Shark biologists Dr. Johan Gustafson
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and Dr. Mariel Familiar Lopez
are here to investigate.
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What's actually happening here
is a behavior called depredation
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and that's when a fisherman's
caught a fish and they're winding it in
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and then a shark will come
and take that fish.
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NARRATOR: Locals claim they are losing as
much as 80% of their catch to the sharks.
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The level of depredation
described by the fishermen
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hasn't been seen anywhere else
in Australia or even the world.
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(dramatic music)
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NARRATOR: Johan and Mariel
have timed their arrival
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with the height
of the tuna fishing season.
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But with a weather front moving in,
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they have just 10 days until strong
winds whip up a powerful swell
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and force their research
vessel back to port.
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We have a variety of equipment
we're going to utilize.
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We've got acoustic tags, cameras,
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and for the first time ever,
a new cage design.
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If what the fisherman are saying is true,
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I want to know why.
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(ominous music)
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NARRATOR: Johan and Mariel team
up with local fisherman, Wade Alleyn.
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Together, they're heading
to one of his favorite fishing spots.
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JOHAN: What's your experience
with the sharks versus the anglers?
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Definitely have an
issue with the bull sharks.
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I believe they've definitely tuned in on
the boats. They relate the boats to food.
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NARRATOR: Bull sharks are often depicted
as mindless, opportunistic killers.
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But they're armed with an array
of high-performance senses
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they could be using
to target the fishermen.
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Smell many times
more powerful than humans.
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Vision that pierces
through the murkiest waters.
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And hearing that can pick up
sound from over a mile away.
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Do you think they're mainly bull sharks,
the ones that are taking the fish?
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I mean, it's hard for us
to identify all the time
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because they'll eat our fish out of sight.
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But there are definitely
a lot of bull sharks down here.
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NARRATOR:
To find out for sure,
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and see if the situation in Weipa
is as bad as the fishermen claim,
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Johan and Mariel
go fishing for themselves.
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MARIEL: We're using a fishing line
camera to be able to ID the shark.
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Is it a bull shark?
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Also, we're going to be able
to see a bit more information
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about the behavior that's occurring.
When does the shark come in?
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There we go. Let's get it in the water.
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Right, we'll send this
all the way to the bottom.
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(tense music)
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How's my technique, Wade?
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WADE: Spot on, mate.
I couldn't do it better myself.
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(dramatic music)
(fishing line whirrs)
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JOHAN: Yep, yeah. (grunts) Oh!
Oh, it's a fish! I got a fish!
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(dramatic music)
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It's taking it down.
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(grunts) Alright, I'll try
and bring it up.
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(grunts) Oh, it's gone!
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-MARIEL: You got bitten off!
-JOHAN: Yep. I think we got sharked.
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NARRATOR:
Within moments of snaring a fish,
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Johan's catch is stolen by an
unmistakable underwater raider,
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a bull shark.
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JOHAN: Wow. That's a big shark.
Over three, three and a half meters.
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The fishing line camera did a great job.
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Alright? We were able
to confirm the species
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and the first fish we caught,
it was taken by a shark in 20 seconds.
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That gives more weight to what
the fishermen are claiming up here.
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This is the first time I've been able to
actually capture a depredation event
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so close-up, underwater. This is amazing.
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MARIEL:
Yeah. It is really amazing footage.
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JOHAN: Now we've seen one shark under
the water from the view of a camera.
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We want to see more. We want to
see are there other sharks around?
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So we need to get in the water with them.
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(dramatic music)
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NARRATOR: In a place as remote as Weipa,
that's a significant challenge.
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You need to remember, we're diving in an
area where sharks have never seen a cage.
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NARRATOR: Sharks have
an acute sense of hearing.
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They use it to locate their prey,
but also keep themselves out of danger.
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Loud, unfamiliar noises
can put them on edge.
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MARIEL: Sound is an important
thing in an aquatic environment
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because it travels four
times faster than in air.
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JOHAN: The thing with sharks is loud,
sudden, sharp noises tend to spook them.
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NARRATOR: The team has come
prepared with a radical prototype
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designed and built by underwater
cinematographer Colin Thrupp.
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A noise canceling cage
made entirely of plastic.
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So how do we reckon this is
going to go when we get in the water?
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Do you reckon these joins
are going to hold?
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I mean, a cage made out
of polyethylene pipe
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sounds a bit nuts
when you first talk about it,
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but when you actually get these
things together, it's pretty strong.
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NARRATOR: A world-first,
the cage has been forged
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using cutting edge electro-fusion welding,
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a technique that bonds plastic
by super-heating it
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to over 200 degrees Fahrenheit.
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I've been told that an earth mover
can hit this and then bounce off.
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MARIEL:
Okay.
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But I haven't heard what
happens if a bull shark hits it.
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-MARIEL: Well we'll test it. (laughs)
-That's what we're here to do.
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We're here to test it. We'll see.
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(energetic music)
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(indistinct speech)
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JOHAN: What I'm hoping
is that these sharks
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become more accustomed
to this plastic cage,
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which is quieter and a
little bit more stealthy.
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It's going to minimize the noise
and hopefully get us closer to the sharks.
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MARIEL: If the plastic cage works
and sharks do come closer,
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this could be a game-changer
of how we study shark behavior,
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not just up here at Weipa
but around the world.
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JOHAN (over radio): Topside, topside.
Please begin lowering the cage.
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NARRATOR: Monitoring the descent
of the experimental cage
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is divemaster, Che McGuiness.
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So, can you give us
an indication of the cage?
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JOHAN (over radio):
The cage is sitting fine, over.
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NARRATOR:
On the surface, Wade casts out.
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The water visibility is unseasonably poor
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but his on-board sonar reveals
there are big animals lurking below.
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COLIN (over radio):
I have a big bull shark, 10 meters out.
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They're staying right
on the edge of our periphery.
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We can only just see them.
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(tense music)
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NARRATOR:
The sharks move in closer,
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and there's more than expected.
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COLIN (over radio): There's at
least six, maybe seven bull sharks
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directly beneath us
right on the edge of the murk.
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(tense music)
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JOHAN (over radio): They're not sure what
we are. They're keeping a safe distance.
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NARRATOR:
Encountering this big pack of bull sharks
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is the first clue something different
is happening in the waters around Weipa.
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A lot of the times I've
seen them just by themselves.
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But here I'm seeing a group
of bull sharks together.
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NARRATOR: Bull sharks are normally
solitary and fiercely territorial.
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They're even known to be cannibalistic.
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Do these sharks
hang out here all the time?
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Do they hang out together all the time?
What's the pecking order in this group?
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We have a lot of work ahead of us
to answer these questions.
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(dramatic music)
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COLIN (over radio):
This is great!
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JOHAN (over radio): All we need now
is for Wade to get a fish on his line.
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CHE:
Divers, divers. Just letting you know.
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The swell and wind has increased
swell and wind has increased.
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If it becomes unsafe or
unworkable, let us know. Over.
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NARRATOR: Another challenge the team
must deal with has reared its head.
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JOHAN (over radio):
Copy that. Let's just see how we go.
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NARRATOR: This year, the whole of
Australia is suffering from La Niña,
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an atmospheric phenomenon
that plays havoc with the weather.
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Recent rainwater has been pouring out of
nearby rivers, reducing ocean visibility.
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Whilst unpredictable winds on the surface
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are churning up
the coastal currents below.
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(dramatic music)
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CHE:
Johan. Johan. Does the cage feel steady?
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JOHAN (over radio):
The cage is bouncing a lot.
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MARIEL: We are concerned
because this is a plastic cage.
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It hasn't been really used a lot of times,
and we haven't really tested it that much.
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NARRATOR:
The lightweight plastic cage
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is being pushed and pulled
by the turbulent water.
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If the ropes connecting it
to the boat snap,
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Colin and Johan could be swimming
unprotected from the sharks.
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CHE:
Johan, Johan, copy?
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(radio static)
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CHE:
Johan, Johan, Johan, do you copy? Over.
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(dramatic music)
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JOHAN (over radio):
Topside, topside can you hear me?
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CHE: I can hear you now.
I can hear you now.
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NARRATOR:
The current's getting stronger.
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Tipping the experimental cage on its side.
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CHE:
Has the cage stabilized, over?
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COLIN (over radio):
The cage is buckling under the pressure.
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You need to get us up now, over.
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CHE:
Coming up now. Coming up now. Over.
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COLIN (over radio):
Copy that.
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(tense music)
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MARIEL: We got you at the surface.
Just wait there for a second.
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NARRATOR: Safely alongside the
mothership the damage becomes clear.
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COLIN: We had raging current
by the end of that,
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you could just see this
thick plume of just muck
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just come through and sweep
us and really tip the cage.
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The plastic cage didn't like it at all
it was really bowing under that pressure.
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JOHAN: We were getting a
little bit banged up underwater,
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but the plastic cage did do
what it was supposed to do.
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We did get close to those sharks,
and they did seem to not be spooked by us.
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I think we had around six to
ten sharks at any one time
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swimming around us up nice and
close. We could almost touch them.
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(indistinct chatter)
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NARRATOR: Johan and Mariel still need
to observe sharks raiding the fishermen
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from underwater.
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But it will take several days for the
cage to be repaired and strengthened.
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COLIN:
Yep! Grounded.
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NARRATOR: It gives them time to
investigate a different question.
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JOHAN:
According to the fishermen,
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it's the noise of their vessels
or the shape of their vessels
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that's attracting sharks
to these fishing grounds.
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NARRATOR: Some locals claim
an even more radical sea-change,
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that the bull sharks have learned
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how to distinguish and follow
individual fishing boats.
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(ominous music)
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MARIEL: Johan and I have
devised a little experiment
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to see if we can prove or disprove
what the fishermen are telling us.
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Are the sharks really
following their boats?
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(dramatic music)
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NARRATOR:
To find out how shrewd the sharks are,
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they need to be tagged
with acoustic transmitters.
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These will monitor their movements.
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But to fit them, the sharks must
be brought alongside the boat.
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JOHAN: In my experience, rod and reel has
always been the best option just for us,
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but also for the welfare of the shark.
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We're there the whole time with it.
We can bring it in quickly.
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We can handle it faster
and we can release it faster.
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NARRATOR:
Johan straps in.
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Landing a shark means going head-to-head
against its power and strength.
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(tense music)
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(fishing line whirrs)
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(dramatic music)
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00:14:56,320 --> 00:15:02,800
JOHAN: Oh, were on! Were on! (grunts)
Yep, we got one! (grunts)
230
00:15:03,920 --> 00:15:08,480
It's a fair bit of weight.
That's a decent shark.
231
00:15:08,560 --> 00:15:11,240
You can feel a strong head movement.
232
00:15:12,920 --> 00:15:15,320
Oh! We are gaining ground, boy!
233
00:15:15,880 --> 00:15:18,360
MARIEL: Once we get the
shark up close to the boat,
234
00:15:18,440 --> 00:15:22,760
we're going to be putting in
a head rope and then a tail rope
235
00:15:22,840 --> 00:15:24,840
and then we're going
to flip it upside down.
236
00:15:24,920 --> 00:15:28,360
So, belly up, to try to put
him in tonic immobility.
237
00:15:29,640 --> 00:15:33,160
NARRATOR: To roll the shark over, the
team need to bring it closer to the boat
238
00:15:33,440 --> 00:15:36,080
and maneuver it with a rope
attached to its tail.
239
00:15:37,480 --> 00:15:40,160
(dramatic music)
240
00:15:40,240 --> 00:15:43,560
-JOHAN: It's definitely a bull.
-MARIEL: Oh, it's a female.
241
00:15:45,680 --> 00:15:47,520
(groans)
242
00:15:47,600 --> 00:15:49,040
-WADE: She's feisty.
-COLIN: She's feisty.
243
00:15:55,000 --> 00:15:57,160
-JOHAN: Tail rope is on.
-COLIN: Good work!
244
00:15:58,800 --> 00:16:01,200
MARIEL: It's upside down,
and she's getting calmer.
245
00:16:02,400 --> 00:16:05,760
Tonic immobility is when
a shark is put belly up.
246
00:16:06,480 --> 00:16:08,840
JOHAN: Basically, they go into
a transient sleep state.
247
00:16:09,560 --> 00:16:11,440
They're not completely asleep or unaware.
248
00:16:12,000 --> 00:16:14,560
They can snap out of this,
so we have to be quite cautious still.
249
00:16:15,640 --> 00:16:17,000
NARRATOR:
The quicker the team works,
250
00:16:17,120 --> 00:16:19,920
the better it will be
for both them and the shark.
251
00:16:20,600 --> 00:16:22,800
First up, the acoustic tag.
252
00:16:24,040 --> 00:16:26,000
JOHAN: It'll allow us to map
the movement patterns
253
00:16:26,080 --> 00:16:28,040
and behaviors of bull sharks in this area,
254
00:16:28,120 --> 00:16:30,680
and it's extremely pivotal
to this experiment.
255
00:16:31,640 --> 00:16:33,400
MARIEL:
Okay. Tag is on.
256
00:16:36,800 --> 00:16:38,720
NARRATOR:
Measuring in at over eight feet,
257
00:16:40,200 --> 00:16:42,280
this bull shark is a prize catch.
258
00:16:43,520 --> 00:16:46,680
The decision is taken to fit
an additional fin camera.
259
00:16:48,160 --> 00:16:51,000
MARIEL: It can tell us so much
about that shark's behavior.
260
00:16:51,240 --> 00:16:53,200
How fast is a shark swimming?
261
00:16:53,280 --> 00:16:57,040
Are they swimming really close to the
surface or are they going really deep?
262
00:16:58,480 --> 00:17:01,880
NARRATOR: This treasure trove of data
will pop off the shark automatically
263
00:17:01,960 --> 00:17:03,040
in a few days.
264
00:17:03,800 --> 00:17:05,840
It's time to release the hook.
265
00:17:06,280 --> 00:17:10,040
JOHAN: Alright, let's get rid
of this thing. Yep, off.
266
00:17:13,240 --> 00:17:14,200
-WADE: Let her free?
-MARIEL: Let it go.
267
00:17:14,280 --> 00:17:16,200
-JOHAN: Let it go.
-MARIEL: Woo-woo!
268
00:17:17,040 --> 00:17:18,800
Perfect. Good release, guys.
269
00:17:19,480 --> 00:17:21,240
(dramatic music)
270
00:17:21,320 --> 00:17:23,360
NARRATOR:
Before they run their experiment,
271
00:17:23,440 --> 00:17:27,440
Johan and Mariel need to fit
as many acoustic tags as possible.
272
00:17:32,120 --> 00:17:36,040
Working like a well-oiled machine,
and with the sharks' welfare in mind,
273
00:17:36,120 --> 00:17:40,000
they catch and swiftly release
four more bull sharks.
274
00:17:40,160 --> 00:17:40,960
JOHAN:
Done!
275
00:17:43,040 --> 00:17:44,400
All these tags that we're putting
276
00:17:44,480 --> 00:17:47,000
is getting us closer to an answer
of what's going on here.
277
00:17:50,240 --> 00:17:52,560
JOHAN: We're going to give
them 24 hours to relax
278
00:17:52,640 --> 00:17:56,480
and go back to a more natural behavior
before we start our experiments.
279
00:17:58,720 --> 00:18:00,400
(music drowns out)
280
00:18:01,040 --> 00:18:03,200
(action music)
281
00:18:04,680 --> 00:18:08,080
JOHAN: The tagging experiment
is designed to prove or disprove
282
00:18:08,160 --> 00:18:11,520
the fishermen's claims that sharks
are following their fishing boats.
283
00:18:12,920 --> 00:18:15,440
NARRATOR: Johan and Mariel
split up into two boats
284
00:18:15,520 --> 00:18:17,840
and both deploy hydrophone receivers.
285
00:18:20,720 --> 00:18:22,880
JOHAN: We can detect the pings
that are coming off those tags.
286
00:18:22,960 --> 00:18:26,720
(sonar static)
287
00:18:27,840 --> 00:18:30,760
NARRATOR: Two of the sharks
they tagged are quickly located,
288
00:18:30,840 --> 00:18:33,880
still lurking together
in the same fishing spot.
289
00:18:34,680 --> 00:18:37,160
MARIEL: Yes Johan.
I've got two of our tagged sharks here.
290
00:18:37,240 --> 00:18:38,040
How about you?
291
00:18:38,440 --> 00:18:40,800
JOHAN (over radio): Uh, hold on.
We're going to come to you. Over.
292
00:18:42,520 --> 00:18:44,240
NARRATOR:
The experiment can begin.
293
00:18:45,960 --> 00:18:51,000
Johan is in Wade's fishing boat. He'll
cast out to get the sharks attention.
294
00:18:51,680 --> 00:18:53,800
Once they're stealing fish off his line,
295
00:18:54,200 --> 00:18:57,400
the fishing boat will move
several miles down the coast.
296
00:18:58,280 --> 00:19:02,680
Mariel will track the tagged sharks from
the second boat to see if they follow.
297
00:19:04,200 --> 00:19:06,440
MARIEL: Johan is going to start
fishing from the other boat
298
00:19:07,040 --> 00:19:09,120
and he's going to wait
for a depredation event.
299
00:19:09,360 --> 00:19:11,440
(tense music)
300
00:19:22,240 --> 00:19:23,320
Yeah. We're hooked up.
301
00:19:23,400 --> 00:19:26,440
(sonar static)
302
00:19:26,520 --> 00:19:27,560
Wow. That's a good-size one.
303
00:19:29,160 --> 00:19:31,320
(machine beeps)
304
00:19:31,400 --> 00:19:34,600
(eerie music)
305
00:19:40,800 --> 00:19:43,280
Oh. No, no, I'm getting
shut. No, that's changed.
306
00:19:43,360 --> 00:19:47,080
I think that's a shark.
That's a shark. Oh! (groans)
307
00:19:47,680 --> 00:19:49,080
(Johan groans)
308
00:19:49,640 --> 00:19:52,400
(tense music)
309
00:19:52,480 --> 00:19:53,920
(groans)
310
00:19:56,800 --> 00:20:00,200
Oh! Oh, no. It's off.
311
00:20:00,280 --> 00:20:05,440
(over radio) Mariel, Mariel? Got bitten
off by a shark. So, it is happening here.
312
00:20:06,320 --> 00:20:08,600
I still got our two tagged sharks here.
313
00:20:09,600 --> 00:20:11,800
JOHAN (over radio): Okay.
Let's pack up everything here.
314
00:20:11,880 --> 00:20:15,880
We're going to move down to the other site
and we're going to see they follow. Okay?
315
00:20:16,440 --> 00:20:17,360
MARIEL (over radio):
Roger that.
316
00:20:20,720 --> 00:20:21,920
NARRATOR:
The big question is:
317
00:20:24,960 --> 00:20:26,760
have the sharks followed?
318
00:20:30,040 --> 00:20:31,520
MARIEL (over radio):
Johan, Johan, do you copy?
319
00:20:32,960 --> 00:20:34,080
Yes, I read you.
320
00:20:34,560 --> 00:20:38,320
I don't pick up any
tagged sharks over here. Over.
321
00:20:40,160 --> 00:20:42,600
JOHAN (over radio): Well look,
we've been here for 30 minutes now.
322
00:20:43,200 --> 00:20:46,160
I think that if they were
following us from there,
323
00:20:46,240 --> 00:20:48,360
we would have picked them up
on the hydrophone by now.
324
00:20:49,400 --> 00:20:54,480
That's a result for us. It means they
haven't followed us from that site.
325
00:20:55,600 --> 00:20:58,440
NARRATOR: The tagged bull
sharks are nowhere to be seen.
326
00:20:59,240 --> 00:21:01,720
But at this new site.
even without fishing,
327
00:21:02,520 --> 00:21:07,600
the on-board sonar reveals a school
of different sharks lining up below.
328
00:21:09,600 --> 00:21:10,800
WADE:
That's a shark there.
329
00:21:12,760 --> 00:21:14,920
JOHAN: That is interesting.
What does this mean?
330
00:21:16,640 --> 00:21:19,680
NARRATOR: The experiment
has delivered an unexpected result.
331
00:21:22,320 --> 00:21:25,360
MARIEL: We don't think that
sharks are following the boats.
332
00:21:26,480 --> 00:21:31,560
What's more likely is this depredation
behavior is much more widespread
333
00:21:31,800 --> 00:21:34,800
in the population of bull sharks
up here at Weipa.
334
00:21:35,320 --> 00:21:37,280
(dramatic music)
335
00:21:37,720 --> 00:21:40,560
NARRATOR: Rather than being
followed by specific sharks,
336
00:21:40,640 --> 00:21:45,640
all the bull sharks in the region may have
learned how to carry out these raids
337
00:21:45,800 --> 00:21:49,400
and could be ambushing the
fishermen wherever they go.
338
00:21:49,840 --> 00:21:50,960
(dramatic music)
339
00:21:51,040 --> 00:21:54,440
We need to remember that this
was just one small experiment
340
00:21:54,520 --> 00:21:55,920
with only a few tagged sharks.
341
00:21:56,760 --> 00:22:01,040
But what it does indicate is that the
scale of these depredation behaviors
342
00:22:01,120 --> 00:22:05,560
could be occurring far more widespread and
intense than what the fishermen realize.
343
00:22:06,400 --> 00:22:10,600
NARRATOR: It could explain why such
a huge proportion of the fishermen's catch
344
00:22:10,680 --> 00:22:11,520
is being taken.
345
00:22:11,960 --> 00:22:14,960
But why do so many bull
sharks in these waters
346
00:22:15,160 --> 00:22:17,440
appear to be conducting these raids?
347
00:22:17,520 --> 00:22:18,800
(dramatic music)
348
00:22:19,920 --> 00:22:23,760
Forces beyond Weipa's shores
are likely playing a role.
349
00:22:23,840 --> 00:22:24,840
(boat horn)
350
00:22:25,040 --> 00:22:30,400
Australian fish stocks have decreased
by 31% over the past decade.
351
00:22:31,160 --> 00:22:34,360
Scientists believe this pressure
could be forcing sharks
352
00:22:34,440 --> 00:22:36,680
to alter their natural hunting behavior.
353
00:22:37,800 --> 00:22:40,880
But it still leaves
many questions unanswered.
354
00:22:42,320 --> 00:22:46,360
JOHAN: We want to know,
why is it so concentrated here in Weipa?
355
00:22:48,080 --> 00:22:49,560
(ominous music)
356
00:22:49,640 --> 00:22:52,480
NARRATOR: Now halfway through
their time in northern Australia,
357
00:22:52,560 --> 00:22:57,760
the team has just five days until strong
winds will force them back to port.
358
00:22:58,760 --> 00:23:01,800
Colin has fixed and strengthened
the plastic cage.
359
00:23:01,880 --> 00:23:05,320
It's ready for him and Johan
to go back in the water.
360
00:23:07,200 --> 00:23:11,760
So far we've only seen the depredation
behavior from the fishing-line camera.
361
00:23:11,960 --> 00:23:15,120
But what we want to do
is see it from the plastic cage
362
00:23:15,200 --> 00:23:17,040
and that's the intention of this dive.
363
00:23:17,760 --> 00:23:19,720
We know that there is
multiple sharks down there.
364
00:23:20,680 --> 00:23:24,800
Wade's up top. He's going to be fishing,
and hopefully we'll be able to see,
365
00:23:24,880 --> 00:23:27,680
is there a hierarchy
between different sized sharks?
366
00:23:28,600 --> 00:23:30,160
What's the etiquette at this dinner table?
367
00:23:32,840 --> 00:23:37,240
NARRATOR: On this dive, a 360-degree
drop camera will help fight back
368
00:23:37,400 --> 00:23:39,920
against the unpredictable
water visibility.
369
00:23:41,240 --> 00:23:44,120
We're really hoping to get
a lot of information from it.
370
00:23:50,760 --> 00:23:52,840
NARRATOR:
The cage is lowered into position.
371
00:23:53,200 --> 00:23:57,120
(tense music)
372
00:23:57,200 --> 00:24:03,560
On the surface, Wade casts out.
Shadows emerge deep in the water.
373
00:24:05,280 --> 00:24:06,880
JOHAN (over radio):
I've got two bull sharks.
374
00:24:06,960 --> 00:24:12,440
Two bull sharks. Approximately
five meters below us. Over.
375
00:24:14,000 --> 00:24:16,000
COLIN (over radio):
The sharks are coming in closer.
376
00:24:18,440 --> 00:24:19,920
JOHAN:
They're getting more confident with us.
377
00:24:22,600 --> 00:24:25,040
COLIN: We've got three
bull sharks around us now.
378
00:24:28,880 --> 00:24:31,520
NARRATOR:
Topside, Wade has a fish on.
379
00:24:31,960 --> 00:24:35,800
(tense music)
380
00:24:35,880 --> 00:24:37,080
JOHAN (over radio):
They're just circling.
381
00:24:38,120 --> 00:24:41,040
COLIN (over radio):
Not coming in too close to take the fish.
382
00:24:44,680 --> 00:24:47,040
NARRATOR:
The sharks are biding their time.
383
00:24:47,560 --> 00:24:51,760
But as the fish on Wade's
line tires, they strike.
384
00:24:52,360 --> 00:24:53,840
JOHAN (over radio):
Big bull coming up, big bull.
385
00:24:57,240 --> 00:24:59,800
Here he comes. He's going for the fish.
386
00:25:09,000 --> 00:25:13,360
(intense music)
387
00:25:16,960 --> 00:25:20,120
COLIN (over radio):
Oh! He's got it! How good was that!
388
00:25:20,800 --> 00:25:23,800
MARIEL: We were expecting to see
the shark come really fast
389
00:25:23,880 --> 00:25:27,200
and just snap it from the line.
But that's not what we saw.
390
00:25:28,560 --> 00:25:31,800
JOHAN: It came in slow.
No sense of urgency at all
391
00:25:32,080 --> 00:25:35,080
and just basically plucked
the fish off the hook.
392
00:25:36,920 --> 00:25:39,360
I've never seen that before.
It was incredible.
393
00:25:40,680 --> 00:25:44,560
Another thing I noticed
was the biting tactic.
394
00:25:44,800 --> 00:25:48,120
So, the sharks took out
the propeller of the fish.
395
00:25:48,280 --> 00:25:50,120
It bit off the tail section first.
396
00:25:50,360 --> 00:25:55,280
And then they came swooping around again,
slow and calm, and they took out the rest.
397
00:25:57,600 --> 00:25:59,320
The general perception about bull sharks
398
00:25:59,400 --> 00:26:02,040
is that they are just
mindless, aggressive hunters.
399
00:26:02,120 --> 00:26:04,120
And that is not what we're seeing here.
400
00:26:04,320 --> 00:26:09,120
What we are seeing is a calm,
more intelligent approach.
401
00:26:10,440 --> 00:26:15,120
NARRATOR: It's strikingly similar to a
tactic used by a legendarily smart hunter.
402
00:26:19,080 --> 00:26:21,880
Killer whales also patiently
stalk fishing boats
403
00:26:22,520 --> 00:26:25,120
striking with intelligent,
surgical precision
404
00:26:25,200 --> 00:26:28,120
once trawlers start
to bring in their catch.
405
00:26:29,160 --> 00:26:33,000
Scientists believe Orcas do this
to deliberately save energy.
406
00:26:34,640 --> 00:26:37,240
Are sharks now rivaling
this clever thinking?
407
00:26:38,720 --> 00:26:40,320
JOHAN: Think of it
from a shark's perspective.
408
00:26:41,520 --> 00:26:43,960
When they hunt,
they expend a lot of energy.
409
00:26:44,560 --> 00:26:46,600
So, a hooked fish presents an opportunity
410
00:26:46,680 --> 00:26:48,960
for a more efficient way
of getting a feed.
411
00:26:52,480 --> 00:26:53,640
NARRATOR:
Back beneath the boat,
412
00:26:54,400 --> 00:26:59,200
underwater cinematographer Colin
catches a glimpse of something unusual.
413
00:27:00,280 --> 00:27:02,520
COLIN (over radio):
I think I can see a smaller bull shark.
414
00:27:02,600 --> 00:27:06,720
(tense music)
415
00:27:06,800 --> 00:27:11,240
Yeah, definitely a young
bull shark. That's really weird.
416
00:27:12,760 --> 00:27:15,680
JOHAN: Col reckons that
he saw a juvenile bull shark.
417
00:27:16,360 --> 00:27:18,120
To me, that's unusual.
418
00:27:18,200 --> 00:27:20,640
Why would there be
a small juvenile bull shark
419
00:27:20,720 --> 00:27:23,080
out in the open ocean in adult territory?
420
00:27:25,080 --> 00:27:27,320
Bull sharks have a really
interesting reproductive cycle.
421
00:27:28,040 --> 00:27:31,040
The females come from the ocean up rivers
422
00:27:31,120 --> 00:27:33,640
to lay their pups
in freshwater environments.
423
00:27:35,120 --> 00:27:38,800
NARRATOR: Rivers offer protection
and security for bull shark pups.
424
00:27:39,560 --> 00:27:43,560
Only once they reach six to seven feet
or around eight years old,
425
00:27:43,640 --> 00:27:44,960
will they head to the ocean.
426
00:27:45,360 --> 00:27:50,200
If Colin did actually see a juvenile
bull shark this far out offshore,
427
00:27:50,400 --> 00:27:51,720
that's quite a significant find.
428
00:27:52,840 --> 00:27:57,360
NARRATOR: It means there could be a bull
shark nursery somewhere nearby.
429
00:27:58,400 --> 00:28:02,760
JOHAN: If that's true, that means juvenile
bull sharks are leaving their nursery
430
00:28:02,960 --> 00:28:06,000
and they're mingling in with these
adults on these fishing grounds.
431
00:28:06,080 --> 00:28:08,600
I think that's something that
needs further investigation.
432
00:28:08,840 --> 00:28:10,000
(tense music)
433
00:28:12,880 --> 00:28:16,240
(action music)
434
00:28:16,320 --> 00:28:17,920
JOHAN:
To prove that there is a nursery,
435
00:28:18,360 --> 00:28:20,320
we need to go and catch
juvenile bull sharks.
436
00:28:20,400 --> 00:28:23,200
And in order for us to do that,
we need to go upriver.
437
00:28:24,480 --> 00:28:28,040
NARRATOR: Located just 30 miles
from the offshore fishing site,
438
00:28:28,120 --> 00:28:30,120
the Mission River runs through Weipa
439
00:28:30,200 --> 00:28:33,520
and is one of the largest
nearby sources of freshwater.
440
00:28:37,120 --> 00:28:41,160
Searching for baby sharks in an
open river is notoriously difficult.
441
00:28:42,480 --> 00:28:44,920
The trick is to follow the food.
442
00:28:47,280 --> 00:28:49,960
We've got a bunch of birds
just hanging off under the bridge.
443
00:28:50,200 --> 00:28:51,800
(birds calling)
444
00:28:52,160 --> 00:28:53,520
JOHAN:
It's good. A lot of birds are a good sign.
445
00:28:55,400 --> 00:28:58,520
NARRATOR: The birds are taking
advantage of a crowded ball of fish
446
00:28:58,600 --> 00:29:00,080
near the surface of the water.
447
00:29:00,840 --> 00:29:04,880
It's a sign that normally means
there are predators lurking below.
448
00:29:07,560 --> 00:29:10,480
COLIN: Where we get little fish
big fish follow, right?
449
00:29:10,640 --> 00:29:11,520
JOHAN:
That's right.
450
00:29:13,760 --> 00:29:15,760
MARIEL: Maybe we should start
to get our gear together.
451
00:29:16,440 --> 00:29:18,520
What do you think
we should put down first?
452
00:29:19,200 --> 00:29:21,920
-Let's go drum lines first.
-Good idea.
453
00:29:23,080 --> 00:29:27,800
NARRATOR: In these silty, low-visibility
waters diving is not an option.
454
00:29:29,200 --> 00:29:33,080
The team needs to bring
whatever's hunting the fish up to them.
455
00:29:34,240 --> 00:29:35,720
JOHAN:
This is really actually quite exciting
456
00:29:35,800 --> 00:29:39,720
because we think that we found a location
where there are juvenile bull sharks.
457
00:29:41,200 --> 00:29:42,920
MARIEL:
We're going to set up some drum lines.
458
00:29:43,000 --> 00:29:45,280
Just think about
a really long fishing line.
459
00:29:46,680 --> 00:29:47,600
JOHAN:
Okay?
460
00:29:47,680 --> 00:29:48,560
-MARIEL: Got it?
-COLIN: Line.
461
00:29:50,120 --> 00:29:51,440
-Perfect.
-Here's your way.
462
00:29:51,960 --> 00:29:54,560
COLIN:
Bring us a little bull shark, please.
463
00:29:56,480 --> 00:29:58,960
JOHAN: Once those yellow floats
are no longer visible,
464
00:29:59,040 --> 00:30:01,280
or if the entire
big float bobs underwater,
465
00:30:02,000 --> 00:30:02,920
we're "shark on."
466
00:30:04,440 --> 00:30:05,480
NARRATOR:
They back off the boat,
467
00:30:06,600 --> 00:30:08,520
and wait for something to bite.
468
00:30:09,280 --> 00:30:14,720
(dramatic music)
469
00:30:14,800 --> 00:30:16,440
MARIEL:
Guys. I think the floats are down.
470
00:30:16,520 --> 00:30:17,960
JOHAN:
All right, cool. Yep, the floats are down,
471
00:30:18,040 --> 00:30:20,040
we can't see the yellows. That's great.
472
00:30:28,360 --> 00:30:31,200
COLIN: He's definitely on. (grunts)
He's still on. He's still on.
473
00:30:31,960 --> 00:30:32,960
There he is. Here he is.
Here he is. Alright.
474
00:30:33,040 --> 00:30:34,640
JOHAN:
Oh, yes. That's a nice little belly.
475
00:30:36,560 --> 00:30:40,120
It looks like-- oh, that could be a bull.
That looks like-- that looks like a bull.
476
00:30:40,200 --> 00:30:42,160
-COLIN: Bull shark!
-JOHAN: This is great. I think we're on.
477
00:30:42,480 --> 00:30:45,920
COLIN:
This is exactly what we came here for.
478
00:30:47,400 --> 00:30:49,360
NARRATOR:
Genetic analyses of this juvenile
479
00:30:49,440 --> 00:30:54,240
could provide vital details
about Weipa's bull shark population,
480
00:30:54,320 --> 00:30:56,840
but only after it's brought
alongside the boat.
481
00:30:57,360 --> 00:30:58,960
COLIN:
Guys, get that tail rope on.
482
00:30:59,040 --> 00:31:00,280
-Thank you.
-COLIN: She's strong.
483
00:31:01,200 --> 00:31:03,480
Hang on, hang on she's come
back around. Swing back round.
484
00:31:05,000 --> 00:31:08,760
NARRATOR: Baby bulls are born
with a mouth full of razor-sharp teeth.
485
00:31:11,360 --> 00:31:13,960
And they're even more agile than adults.
486
00:31:15,440 --> 00:31:16,360
(all exclaim)
487
00:31:16,440 --> 00:31:17,720
JOHAN: He's going--
he's going too far forward.
488
00:31:18,840 --> 00:31:21,680
-Just keep this in gear, in back here.
-COLIN: You got it.
489
00:31:22,440 --> 00:31:24,160
JOHAN: They might be small,
but they still can bite.
490
00:31:25,360 --> 00:31:27,080
Fighter, yeah. I lost it.
491
00:31:27,160 --> 00:31:28,800
(dramatic music)
492
00:31:30,680 --> 00:31:32,320
-COLIN: Whoa!
-JOHAN: He's a fighter.
493
00:31:32,400 --> 00:31:33,400
That's great.
494
00:31:33,480 --> 00:31:35,440
(tense music)
495
00:31:35,680 --> 00:31:37,080
-JOHAN: Towing, off. Ready?
-COLIN: Yes!
496
00:31:37,160 --> 00:31:37,960
JOHAN:
Grab that rope.
497
00:31:39,920 --> 00:31:41,680
MARIEL AND COLIN:
Oh, it's a female.
498
00:31:42,480 --> 00:31:44,240
MARIEL:
Hello, cutey.
499
00:31:45,120 --> 00:31:48,880
-NARRATOR: The shark is under control.
-JOHAN: It's one meter 40.
500
00:31:49,640 --> 00:31:52,880
I would say she's been here,
for about five years.
501
00:31:53,800 --> 00:31:55,560
NARRATOR:
Measuring under five feet,
502
00:31:55,760 --> 00:31:59,160
it's highly unlikely this shark
traveled here by sea.
503
00:32:00,040 --> 00:32:01,800
She's definitely from this river system.
504
00:32:02,880 --> 00:32:04,840
So, I'm pretty confident there's
even smaller ones around.
505
00:32:06,640 --> 00:32:07,920
Capturing this juvenile bull shark
506
00:32:08,560 --> 00:32:11,160
indicates that there is
a nursery in this river.
507
00:32:12,400 --> 00:32:14,520
This means that there is
an easy connection
508
00:32:14,600 --> 00:32:18,640
between this nursery
and the offshore population.
509
00:32:20,040 --> 00:32:22,840
NARRATOR: An easy connection
means more opportunities
510
00:32:22,920 --> 00:32:26,600
for juveniles to mingle
with adult sharks out at sea.
511
00:32:28,600 --> 00:32:33,440
Bull sharks don't have parental care,
and they're usually solitary animals.
512
00:32:34,080 --> 00:32:37,880
So, seeing them interact together,
we get a lot of questions.
513
00:32:39,480 --> 00:32:43,160
Previous research has shown
that a lot of species, including sharks,
514
00:32:43,240 --> 00:32:47,280
have the ability to learn new
behaviors in a social setting.
515
00:32:47,840 --> 00:32:49,480
Is that how bull sharks in Weipa
516
00:32:49,560 --> 00:32:52,400
are actually picking up
this depredation behavior?
517
00:32:53,040 --> 00:32:55,440
(dramatic music)
518
00:32:55,520 --> 00:32:57,600
NARRATOR:
Catching a juvenile bull shark
519
00:32:57,680 --> 00:33:01,520
also allows Johan and Mariel
to test another theory.
520
00:33:02,120 --> 00:33:04,040
Alright, were going to
need a biopsy sample.
521
00:33:05,720 --> 00:33:08,440
Bull sharks tend to migrate
with the seasons
522
00:33:08,520 --> 00:33:10,360
because the water temperature changes.
523
00:33:10,920 --> 00:33:15,280
So as it cools, bull sharks will move
into the more constant warmer waters.
524
00:33:16,120 --> 00:33:20,440
NARRATOR: But that rule might not apply in
this tropical part of northern Australia.
525
00:33:21,600 --> 00:33:22,440
JOHAN:
Up here in The Top End,
526
00:33:22,520 --> 00:33:24,560
the water temperature doesn't
really fluctuate as much.
527
00:33:26,400 --> 00:33:27,680
NARRATOR:
The sharks around Weipa
528
00:33:27,760 --> 00:33:32,360
could be resisting their migratory
instincts and putting down roots.
529
00:33:33,200 --> 00:33:35,600
JOHAN: If that's true and they
are staying in the one area,
530
00:33:36,480 --> 00:33:38,640
that means social learning behaviors
531
00:33:38,720 --> 00:33:42,600
could be offloaded
to younger sharks more often.
532
00:33:44,240 --> 00:33:47,680
NARRATOR: Proving this theory
will take years of field work and tagging.
533
00:33:48,360 --> 00:33:53,120
But cutting-edge genetic analysis
could offer a sneak-peek at the results.
534
00:33:54,960 --> 00:33:57,480
DNA can tell us
a lot of interesting stuff.
535
00:33:58,080 --> 00:34:01,760
We can test it against other
populations around Australia.
536
00:34:01,840 --> 00:34:05,560
It can tell us if there's
any genetic differences.
537
00:34:05,640 --> 00:34:09,240
It can also tell us how related
sharks are to each other.
538
00:34:10,480 --> 00:34:11,320
JOHAN:
I think we're good here.
539
00:34:11,400 --> 00:34:13,400
I think we can get ready to release,
so we're going to take off the tail rope.
540
00:34:14,120 --> 00:34:15,120
MARIEL:
Okay, tail's out.
541
00:34:17,880 --> 00:34:18,680
COLIN:
Off she goes.
542
00:34:21,560 --> 00:34:23,160
COLIN:
Whew! How good?!
543
00:34:23,240 --> 00:34:26,160
-Oh, nice. That was great.
-Yes! What fun!
544
00:34:27,840 --> 00:34:29,880
NARRATOR:
To complete their investigation
545
00:34:29,960 --> 00:34:34,440
and find out if the bull sharks around
Weipa are putting down roots,
546
00:34:34,840 --> 00:34:40,600
Johan and Mariel need to get DNA samples
from adult sharks back out at sea.
547
00:34:43,280 --> 00:34:45,960
On the way, there's a temporary diversion.
548
00:34:46,040 --> 00:34:48,040
(beeping)
549
00:34:48,120 --> 00:34:49,480
NARRATOR:
A ping from the fin cam
550
00:34:49,720 --> 00:34:53,000
they attached to a big bull shark
several days ago.
551
00:34:53,680 --> 00:34:55,360
(beeping, continuous)
552
00:34:55,560 --> 00:34:58,120
We're trying to find it
by tracking its signal
553
00:34:58,200 --> 00:35:00,160
so we can download and get the data.
554
00:35:02,800 --> 00:35:05,080
MARIEL:
I think it's coming near the shore.
555
00:35:09,160 --> 00:35:10,000
JOHAN:
There it is.
556
00:35:11,880 --> 00:35:13,240
MARIEL:
Oh yeah, I can see it.
557
00:35:18,360 --> 00:35:22,640
JOHAN: The data from the fin cam
showed us some amazing information.
558
00:35:23,440 --> 00:35:25,320
Generally, bull sharks that I've tagged
559
00:35:26,480 --> 00:35:29,680
spend more of their time
at the ocean floor during the day.
560
00:35:30,640 --> 00:35:34,520
NARRATOR: Normally they use the
cover of night to patrol at the surface.
561
00:35:35,400 --> 00:35:37,000
That's not what we're
seeing here in Weipa.
562
00:35:37,880 --> 00:35:41,480
We're seeing the bull shark
spending time at the water's surface
563
00:35:41,920 --> 00:35:45,120
and then going all the way back down
to the sea floor during the day.
564
00:35:45,800 --> 00:35:49,360
NARRATOR: The fin cam
captures the shark repeatedly diving
565
00:35:49,440 --> 00:35:51,240
and then returning to the surface.
566
00:35:52,800 --> 00:35:54,840
JOHAN:
This is what we call "yo-yo diving."
567
00:35:54,920 --> 00:35:59,480
The yo-yo behavior is generally associated
with a type of patrolling behavior.
568
00:35:59,560 --> 00:36:01,160
Basically, the shark's looking for food.
569
00:36:02,400 --> 00:36:07,320
But why is this bull shark doing it during
the day when they're generally nocturnal?
570
00:36:08,160 --> 00:36:09,320
That is a significant question.
571
00:36:10,200 --> 00:36:13,320
NARRATOR: It's yet another anomaly
amongst the local bull sharks.
572
00:36:15,040 --> 00:36:17,840
Is it somehow related
to the recreational fishing?
573
00:36:18,920 --> 00:36:21,400
Are they looking for
recreational fishing catches?
574
00:36:25,000 --> 00:36:26,320
This is a good piece of the puzzle,
575
00:36:27,400 --> 00:36:30,800
but we have to remember
that it is only one animal,
576
00:36:30,880 --> 00:36:36,880
one incident in one video shot so far,
but it does start to raise questions.
577
00:36:37,480 --> 00:36:40,280
To conclude something,
we really need to get more data first.
578
00:36:42,880 --> 00:36:44,800
(ominous music)
579
00:36:44,880 --> 00:36:47,040
NARRATOR:
It's the team's final day in Weipa.
580
00:36:48,400 --> 00:36:51,560
Strong winds will soon force
the mothership back to port.
581
00:36:53,640 --> 00:36:57,680
JOHAN: This is our last dive here.
And we need to get more DNA samples.
582
00:36:58,320 --> 00:37:01,680
Basically, the higher the number
of biopsy samples we have
583
00:37:01,840 --> 00:37:05,160
is the greater our strength in our
conclusions that we can come up with.
584
00:37:08,600 --> 00:37:13,000
NARRATOR: To collect the DNA,
Johan is armed with a modified spear gun.
585
00:37:13,560 --> 00:37:18,720
This will maximize his chances of getting
multiple samples from one dive.
586
00:37:21,640 --> 00:37:25,440
Wade fishes topside once again
to draw the sharks in.
587
00:37:30,400 --> 00:37:34,600
COLIN (over radio): Yes, we've got two
sharks below us. Two sharks. Over.
588
00:37:37,160 --> 00:37:39,160
MARIEL:
Although we're seeing the bull sharks,
589
00:37:39,800 --> 00:37:41,400
we still need to get them
a little bit closer
590
00:37:41,480 --> 00:37:43,640
so that we can get
a biopsy sample from them.
591
00:37:44,880 --> 00:37:47,280
NARRATOR:
The cage is positioned closer to Wade
592
00:37:47,800 --> 00:37:50,800
to increase Johan's
chances of a clean shot.
593
00:37:53,400 --> 00:37:55,200
COLIN (over radio):
Bull shark at 12 o'clock.
594
00:37:56,320 --> 00:37:57,520
six or seven meters out.
595
00:37:58,000 --> 00:37:59,280
(suspenseful music)
596
00:37:59,520 --> 00:38:01,080
NARRATOR:
It's high-noon for Johan,
597
00:38:01,280 --> 00:38:05,320
but before he's had a chance
to pull the trigger, disaster.
598
00:38:06,600 --> 00:38:08,280
COLIN (over radio):
There's this murk coming through.
599
00:38:09,320 --> 00:38:11,600
NARRATOR:
A cloud of silt envelopes the cage.
600
00:38:12,760 --> 00:38:14,560
JOHAN (over radio):
We're right on the edge of visibility.
601
00:38:16,520 --> 00:38:19,760
NARRATOR: Giant bull sharks
just meters away from the divers
602
00:38:19,840 --> 00:38:21,120
have become invisible.
603
00:38:22,480 --> 00:38:25,800
COLIN (over radio): The visibility
is getting worse and worse.
604
00:38:26,760 --> 00:38:27,920
NARRATOR:
With fish in the water,
605
00:38:28,080 --> 00:38:32,360
an unseen shark could easily
collide with the cage.
606
00:38:32,440 --> 00:38:34,680
(intense music)
607
00:38:40,920 --> 00:38:44,520
CHE: Surface to divers,
we have a 20-minute bottom time
608
00:38:44,600 --> 00:38:48,600
due to conditions have just started
to creep up, up here.
609
00:38:48,680 --> 00:38:51,480
Okay divers, you've got 20 minutes,
20 minutes, 20 minutes.
610
00:38:53,720 --> 00:38:56,480
NARRATOR: Time is running out
to get the DNA samples.
611
00:38:56,560 --> 00:39:01,760
(tense music)
612
00:39:01,840 --> 00:39:04,120
COLIN (over radio):
Johan. Bull shark to your left.
613
00:39:09,520 --> 00:39:13,440
Coming in closer.
Take the shot! Take the shot!
614
00:39:17,280 --> 00:39:18,960
Got him! Yes!
615
00:39:21,400 --> 00:39:22,840
NARRATOR:
It's the perfect shot.
616
00:39:24,320 --> 00:39:28,040
The shark is none-the-wiser
and disappears as if nothing's happened.
617
00:39:29,920 --> 00:39:33,760
CHE (over radio): Divers. Divers. Five
more minutes. Five more minutes. Over.
618
00:39:34,760 --> 00:39:37,400
NARRATOR: There's still
a few more minutes on the clock.
619
00:39:37,920 --> 00:39:40,680
(dramatic music)
620
00:39:47,480 --> 00:39:48,920
COLIN (over radio):
We've got another one coming in.
621
00:39:53,640 --> 00:39:57,840
Yes! A second biopsy
in the bag. Nice shot.
622
00:39:58,720 --> 00:40:01,200
NARRATOR:
It's another crucial sample.
623
00:40:02,040 --> 00:40:05,640
COLIN (over radio): Divers to surface.
You can start bringing us up.
624
00:40:06,560 --> 00:40:07,680
Mission success.
625
00:40:10,000 --> 00:40:12,760
CHE: Copy, copy.
We'll bring you close to the surface.
626
00:40:18,040 --> 00:40:19,640
COLIN (laughs):
That was a better dive, wasn't it?
627
00:40:19,720 --> 00:40:22,720
JOHAN (laughs): That was awesome. That
was great. It actually worked really well.
628
00:40:23,160 --> 00:40:24,760
I don't know about you,
but I count that as a win.
629
00:40:25,040 --> 00:40:25,960
JOHAN: I think we've done well.
630
00:40:26,760 --> 00:40:30,720
NARRATOR: Despite the unpredictable
weather, the team have what they need.
631
00:40:31,800 --> 00:40:36,200
We got several biopsy samples from
a range of different sizes of bull sharks
632
00:40:36,280 --> 00:40:38,760
that we've sent
to the laboratory to analyze.
633
00:40:42,160 --> 00:40:44,360
(dramatic music)
634
00:40:44,440 --> 00:40:46,440
NARRATOR:
The DNA results are in.
635
00:40:47,400 --> 00:40:52,720
It's a small sample size, but they've
delivered truly intriguing data.
636
00:40:54,120 --> 00:40:58,440
JOHAN: What the DNA has shown us,
is that the shark we sampled upriver
637
00:40:59,480 --> 00:41:01,480
is half related to the large female
638
00:41:01,560 --> 00:41:03,880
that we sampled offshore
in that last cage dive.
639
00:41:06,040 --> 00:41:08,840
NARRATOR: Further analysis
indicates that the third sample
640
00:41:09,440 --> 00:41:12,760
is also related to both these sharks.
641
00:41:14,840 --> 00:41:19,440
JOHAN: Due to the small sample size
that we have, I'm completely surprised,
642
00:41:19,520 --> 00:41:24,480
and I did not expect any of these sharks
to be in any way related to each other.
643
00:41:26,240 --> 00:41:28,080
MARIEL: We don't know
if it's a mother or a father
644
00:41:28,360 --> 00:41:32,960
but we do know that they're sharing
an ancestor in-between them.
645
00:41:35,200 --> 00:41:38,680
NARRATOR: It's a strong family link
connecting the bull sharks in the nursery
646
00:41:39,640 --> 00:41:41,960
to the adults raiding
the fishermen at sea.
647
00:41:45,040 --> 00:41:48,680
JOHAN: It may also implicate
that compared to other areas
648
00:41:48,760 --> 00:41:51,400
these sharks may not
be moving in large numbers.
649
00:41:52,520 --> 00:41:56,080
NARRATOR: The closer related the
sharks, the smaller the gene pool,
650
00:41:56,320 --> 00:41:58,440
and the less they could be moving away.
651
00:41:58,920 --> 00:42:01,400
JOHAN: If they're not
migrating the large distances
652
00:42:01,480 --> 00:42:04,240
and they're spending
more time in this one area,
653
00:42:05,040 --> 00:42:07,920
that could explain why
the depredation events
654
00:42:08,000 --> 00:42:11,080
are so much higher
and concentrate here in Weipa.
655
00:42:11,720 --> 00:42:13,760
(dramatic music)
656
00:42:14,040 --> 00:42:17,680
MARIEL: If the populations of bull sharks
up here at Weipa are localized,
657
00:42:17,760 --> 00:42:22,200
they would be exposed
constantly to fishing activities,
658
00:42:22,800 --> 00:42:26,600
increasing their likelihood
of depredation behaviors.
659
00:42:30,640 --> 00:42:34,000
NARRATOR: Together with the presence
of the nearby bull shark nursery,
660
00:42:34,840 --> 00:42:39,080
it could put Weipa at the
epicenter of a perfect storm.
661
00:42:40,640 --> 00:42:43,400
MARIEL: It's definitely possible
that juvenile bull sharks
662
00:42:43,600 --> 00:42:45,960
could be learning
the behaviors from adults.
663
00:42:46,520 --> 00:42:50,920
JOHAN: We've seen smaller
sharks leaving the river earlier…
664
00:42:51,000 --> 00:42:52,560
JOHAN (over radio):
Definitely a young bull shark.
665
00:42:52,640 --> 00:42:56,240
JOHAN: …and potentially
starting the social interactions
666
00:42:56,320 --> 00:42:58,560
and learning procedures at a younger age.
667
00:42:59,720 --> 00:43:02,520
MARIEL: Seeing this bull shark
behavior has been amazing.
668
00:43:02,600 --> 00:43:04,200
However, it's also been surprising.
669
00:43:06,120 --> 00:43:08,320
NARRATOR: The raids on
fishermen have been exposed
670
00:43:08,400 --> 00:43:11,520
as the work of a methodical,
calculated hunter.
671
00:43:13,680 --> 00:43:15,240
They're highly intelligent.
672
00:43:15,680 --> 00:43:20,000
They're analyzing their environment
before they do anything.
673
00:43:21,600 --> 00:43:24,360
NARRATOR: These smart bull sharks
might be at the vanguard
674
00:43:24,440 --> 00:43:28,840
of an adapting shark behavior
that could soon spread elsewhere.
675
00:43:31,960 --> 00:43:35,120
JOHAN: Recreational fishing
is increasing worldwide.
676
00:43:36,080 --> 00:43:38,920
We're starting to see a lot
more anger towards sharks,
677
00:43:39,480 --> 00:43:43,520
and that could lead to a downward
spiral towards shark conservation.
678
00:43:44,880 --> 00:43:48,320
That's why it's important when we get
opportunities like up here in Weipa
679
00:43:49,280 --> 00:43:51,200
that we grab them with both hands.
680
00:43:52,520 --> 00:43:53,960
There's a lot more to uncover.
681
00:43:54,040 --> 00:43:57,560
And I am looking forward to coming back
and spending a lot more time here.
682
00:43:58,040 --> 00:44:00,200
(dramatic music)