All language subtitles for s01e04 The Great Tide.eng

DAVID ATTENBOROUGH:
The power of the sun drives the seasons,

transforming our planet.

Vast movements of ocean and air currents

bring dramatic change
throughout the year.

And in a few special places,
these seasonal changes

create some of the greatest
wildlife spectacles on Earth.

The most dramatic event
in the world's oceans

happens off the eastern shores
of South Africa.

These cool waters create
the perfect conditions

for a spectacle of epic proportions.

And everything revolves
around the humble sardine.

Each year millions of them
are swept up Africa's coast

on a desperate winter journey.

Following them comes what will become
the biggest army of predators

anywhere on the planet.

The climax to this chase depends
on many crucial elements coming together

for one brief moment in time.

This can well claim to be
the greatest ''shoal'' on Earth.

In the deep water
off the southern tip of Africa

lie the rich fishing grounds
of the Agulhas Bank.

It's home to billions of sardines.

They live in immense shoals as
defence against their many predators.

Moving together as one in a shoal

gives an individual sardine
its best chance of survival.

Sardines are so numerous,

they're on the menu
of most fish-eating predators here.

It's summer, and the sardines are lost
in the vastness of the ocean.

The shoals are so dispersed
they're hard to find.

Common dolphins
are specialist sardine hunters.

Dolphins aren't
the only ones on their trail.

Gannets also rely on a diet of sardines.

The best way for them to find the shoals
is to follow the dolphins.

When the fish are far out to sea,

the dolphins need great perseverance
to track them down.

The dolphins use
their own form of sonar,

sending out a stream
of clicks and whistles,

listening for returning echoes.

(CLICKING)

At last they've found
what they're looking for.

Working as a team,
the dolphins isolate a group of fish

and corral them into a tight ball
close to the surface.

The gannets can now make their move.

Gannets can't dive deep,

so they must rely on dolphins
to keep the sardines near the surface.

The feeding frenzy is short-lived.

Most of the shoal escapes to the deep
and the hunters are left still hungry.

It's December,
the height of the southern summer,

and the sardines have the advantage.

With the shoals dispersed,
life is hard for all the predators.

But in six months' time,
if conditions are right,

the scene will be set for
astonishing and sustained drama.

For a few short weeks each winter,

cold ocean currents can sweep
great shoals of sardines up the coast.

Trapped close to shore
within this corridor of cool water,

the fish are vulnerable and
their predators will follow in droves.

If it happens,
this will be the Sardine Run,

one of nature's great events,
unique to these shores of South Africa.

But for this epic event to take place,
many elements have to come together,

and with our changing climate
they're less predictable every year.

For the predators,
the winter Sardine Run, if it happens,

can make the difference
between life and death.

Dolphins rely on the easy hunting
during the run to wean their calves.

But the omens aren't good.

Last year the sardines
didn't run at all.

Gannets follow the same pattern.
They have their chicks in summer,

so they, too, leave the nest
in time for the Sardine Run.

This is Bird Island,
just off the Eastern Cape,

the biggest gannet colony in the world.

No less than 1 00,000 breeding pairs

come here every summer
to have their young.

These incredible numbers
show the wealth of life

the annual Sardine Run can support.

They also show how many lives
may be in jeopardy

if the sardines don't run.

Right now the African summer
is taking its toll.

With temperatures soaring
and no cover on these exposed islands,

the birds are in danger of overheating.

The young are especially vulnerable.

They have to be fed every day.

Even with both parents taking turns,
it's an exhausting task.

In summer the sardines are
a long way out to sea.

The birds fly hundreds of miles
in search of a meal.

Once they've sighted their target,
they plunge from heights of 30 metres...

striking the water at 60 mph.

Every dive subjects them
to enormous forces.

The slightest miscalculation
could be fatal.

Gannets dive no deeper than 1 0 metres,

so once again they rely on the dolphins
to keep their prey near the surface.

But with so much traffic, there's
always the danger of a collision.

This one has broken her neck.

Her death will mean
that back on the colony

her chick will probably starve.

The rest make the long flight home
with their catch.

One partner stays on the island
to guard their chick.

The pair welcome each other
with a ritualised greeting.

They have a strong bond
and many couples mate for life.

During the hours of daylight
the sardines stay deep

in an attempt to avoid their predators.

As the sun sets, the little fish
themselves can begin to feed.

They swim upwards
to sieve the water for plankton,

microscopic plants and animals.

At daybreak they sink once more
into the safety of the deep.

It's not just dolphins and gannets
that rely on sardines.

There are other,
more mysterious predators.

The Bryde's whale
hardly breaks the surface to breathe

and never so much as shows a tail fluke.

For a 1 5-metre whale,
they can vanish with remarkable ease.

We know little
about these stealthy leviathans,

other than that they are
sardine-hunters, too.

Summer is a lean time
for the Bryde's whale,

as it is for all the predators.

Sharks follow the same patterns,

tracking the shoals offshore
through the summer,

waiting for the winter Sardine Run
when the hunting will be easier.

But being cold-blooded,

they don't have the high energy demands
of the whales, dolphins and gannets.

All the predators
have to endure the lean months,

relying on the southern winter in June
to bring a change in their fortunes.

Now the changing seasons
create a switch in the ocean currents.

As summer gives way to autumn,

the southerly-flowing
warm current weakens

and cold Antarctic water
pushes further north, nearer to land.

The sardines are carried along
by these cool waters

and pushed closer to shore.

If these ocean currents
continue to change,

the Sardine Run should be
only three months away.

It's time for the gannet chicks
to leave the safety of their colony.

Parents stop feeding their young
when they're three months old.

This forces the chicks
to take to the sea.

The young have enough fat reserves
to survive for just 1 0 days.

And in this brief window,

they must learn how to fly
and hunt for themselves.

This is the most critical time
in a gannet's life.

Failure will mean starvation.

To prepare for their maiden flight,

they test their wings
and strengthen their flying muscles.

Eventually, hunger drives them
onwards and upwards.

Some get up and away first time.

But many don't make it
past the crashing surf.

Some bedraggled chicks
struggle back to shore.

But for others,
the pounding has been too much.

Fewer than half
of all the chicks on this colony

survive their first three months
of life.

The coast of South Africa
is an unforgiving place.

The baby dolphins
are still dependent on their mothers.

They suckle for six months before they,
like the young gannets,

have to start fishing for themselves.

There is such an abundance of fish
during the Sardine Run,

that even the calves can catch some and
so begin to learn their hunting skills.

But the Sardine Run
might not even happen this year.

For now the dolphins will have to
continue to scour the vast ocean.

Back at the coast, other youngsters
are getting ready to go it alone.

Cape fur seals are also waiting
for the sardines to come close to shore.

But seals have a broad diet,

so they can make the most
of other feeding opportunities

until the sardines come within range.

Young seals are forced from the colony
by the dominant males.

Once they're cast out, the adolescents
roam the coastline looking for food.

They won't turn their noses up
at a plump young gannet.

Hungry seals patrol the surf,

ready to pick off any birds that
don't get airborne straight away.

When the wind is light, the gannet
chicks are stuck on the island.

Surely they're safe here?

But even on land the seal is
surprisingly fast on his flippers.

In this one season,
on this one colony alone,

seals kill up to1 0,000 fledglings.

And, as ever,
it all comes down to sardines,

for the seals are only after the fish
within the stomach of their victims.

For the young birds
who do make it past the seals,

there are fresh challenges.

Learning the skills of their parents.

First they have to find their quarry,
the sardine shoals.

And the best way to do that
is to follow the expert trackers.

They're hungry. It's been days
since their parents last fed them.

As the search goes on,

the chicks are learning
the most sophisticated

survival technique of all -

how to harness the expertise
of another species.

After a long search,

the dolphins have found
a small school of fish.

They drive the sardines to the surface
and within range of the young gannets.

Now, quickly, they have to learn
the art of the plunge-dive.

But there's a problem.

The opportunistic seals
have found the fish, too.

The young gannets
have a daunting choice.

To risk diving with the enemy
or to starve.

If they don't take their chances soon,
there will be nothing left.

They're in luck.

With sardines back on the menu,
the seals ignore the gannets.

As ever, the dolphins have
done the hard work

of rounding up the fish,

and now a host of other predators
take advantage.

With the shoal diminishing
by the second, competition is fierce.

But there is still time
for a mighty intruder.

The Bryde's whale
devours the entire ball of fish.

Until the Sardine Run starts in earnest,

these minor skirmishes are
mere preludes to the main event.

But winter is finally on the way.
The cold current pushes further north.

This cool water
forces its way up the coast.

If it continues to flow northwards,

it will carry
great shoals of sardines with it.

The predators begin to gather,
in anticipation of a feast.

Sardines can't tolerate water
above 20 degrees centigrade.

So unless the cool water
penetrates further up the coast,

the fish won't move and
the annual run just won't happen.

Perhaps climate change
has made its mark here.

The waters have stayed too warm,
stalling the movement of fish.

There hasn't been a sardine run
for the past two years.

The entire fleet is becalmed.

A winter storm rolls in
from the Antarctic,

battering the Cape, bringing cold water.

Driven by their hunger,

gannets still try to hunt
in these dangerous conditions.

In fact, this wild weather

is just what all the predators
have been waiting for.

For them, it's a perfect storm.

It has pushed a narrow tongue
of colder water up the coast.

This chilly current carries wave
after wave of sardines with it.

Hemmed in by the land on one side
and warm water on the other,

the sardines are
being drawn into a trap.

Nature is playing a cruel trick
on these unfortunate fish,

as they'll get no benefit
from their mass voyage.

They're slaves
to the cold ocean currents.

More than 500 million fish
are swimming towards disaster,

and yet this is just a tenth
of the sardine population.

The run is on.

Ahead, an ambush is being prepared.

As the seas begin to calm,

the dolphins relocate
the sardine shoals.

As they track up the coast,
the pods unite, combining forces.

They form super-pods
of incredible numbers,

up to 5,000 dolphins in one group.

This is fast becoming one of
the biggest groups of predators

anywhere on the planet.

The attackers spread out
into wide hunting lines,

stretching up to a mile across.

Other divisions follow on,
as ever tracking the dolphins.

Shadowing them all, the Bryde's whale.

They're all heading in one direction,

towards a place
known as Waterfall Bluff.

It's an arc in the coastline
which interrupts the flow of currents,

trapping the water in a swirling eddy.

And the dolphins know
that the massive shoals

often get caught in this bottleneck.

But these sardines
have managed to avoid the trap.

The first shoals have been carried
well to the north of Waterfall Bluff,

ahead of the dolphin super-pods.

As the cool water is squeezed
into an ever thinner band

closer to the shore,

the shoals are forced up
into the shallows.

Only now do we get a real sense
of the sheer volume of fish.

This one shoal stretches
along the coast for 1 5 miles.

The water is 1 5 metres deep

and packed with sardines
from top to bottom.

There could be more than 1 00 million
fish in this single shoal alone.

As long as the sardines
are in such shallow water,

they're beyond
the reach of the dolphins,

who won't follow for fear of stranding.

And the gannets can't risk diving
into such shallow water either.

But there are hunters who can follow.

And they've arrived in their thousands.

Sharks.

Dusky, copper and ragged-tooth sharks
encircle the sardines.

But for the little fish,
there's safety in such vast numbers.

The sheer volume of sardines,
the way they twist and turn in harmony,

confuses the sharks.

Without dolphins to round up the fish,

these sharks have to
find their own solution.

They try to trap the fish
against the water's surface.

But this boiling water
is mostly sardines escaping.

Few are actually eaten.

Tiny fish triumph
over the marauding sharks.

The sharks continue to harry the shoal,
pushing it ever northwards.

Back at Waterfall Bluff,
the dolphins and gannets

are waiting for the next
pulse of sardines

to come up from the south.

If there is another shoal,

this kink in the coastline
is the perfect place to ambush them.

But if the fish don't come,

these hungry predators face a long
journey all the way back to the Cape.

To the north,
the survivors of the shark attack

are nearing the end of their run
at the beaches around Durban.

These seem like the lucky ones.

On their epic journey
they've evaded an army of hunters.

But one final, unexpected
predator lies in wait.

Fishermen can only net the sardines
once they've swum this far north,

within easy reach of the shore.

Last year no sardines
were seen on this coast.

So far this winter, the fishermen
have landed only 50 tonnes,

barely a tenth of what they'd expect
in a good year.

That's how unpredictable
the Sardine Run has become.

After such a long and hazardous voyage,

it's a sad end for these sardines.

At Waterfall Bluff, the dolphins
and gannets have had to bide their time.

After missing the first shoal,

these predators
are relying on the currents

to sweep another big pulse of sardines
up the coast.

Now another great shoal is on the way.

And it's heading straight
for Waterfall Bluff.

Trapped between the shore on one side
and the warm water on the other,

these fish are swimming straight
towards the enemy.

The sardines fall back
on their instinctive defence,

swarming into a huge mass
that confuses a predator.

But the dolphins have a strategy
that turns this to their advantage.

Working together,
they separate off a pocket of sardines.

In smaller numbers the fishes
shoaling defence now works against them.

The dolphins corral the bait ball
and herd it to the surface.

This is what the other hunters
have been waiting for.

Now the sardines are within range
of the gannets.

The bait balls form and reform,

seldom lasting longer than
a few minutes each.

The sharks pile in, taking advantage
of the dolphins' hard work.

The predators ignore each other.
There's only one victim here -

the millions of tasty little fish
they've been stalking for so long.

Young gannets join the frenzy.

In just six months they have become
superb aerial hunters.

Time after time, the dolphins round up
another shoal for destruction.

Frantically, the little fish
try to get away

from the seething surface of the water
to dive beyond the range of the gannets.

Now,
something truly astonishing happens.

Diving takes the gannets
down to 1 0 metres.

Then the aerial squadrons
become shoals of swimmers

as they pursue the fish
down to 20 metres.

Sardines join with their predators

in a beautiful
yet macabre underwater ballet.

There's little chance of escape
for these fish.

The stage is set
for the biggest predator of all.

The Bryde's whale takes in
1 0,000 fish in one giant mouthful.

But this time around,
there are plenty of sardines for all.

Each hunter amongst these millions
plays its part in the drama

and each is dependent upon the other.

The annual spectacle of the Sardine Run

is undoubtedly the greatest gathering
of predators anywhere on the planet.

It's surely
one of nature's great events.

Then, almost as quickly as it began,

it's over.

As the brief winter comes to an end,

warm currents flowing south
displace the corridor of cool water.

Despite the massacre,

more than half of all the sardines
swept up on the great run, survive.

As the currents switch,

the fortunate ones
make good their escape.

From here,
they'll follow deep water currents,

hitching a ride
back to the cool waters of the Cape.

The Bryde's whale melts away
to resume its secretive life

somewhere out in the big blue.

The dolphin super-pods break up and
begin their long trek back to the Cape.

Gannets, too, head south.

As Waterfall Bluff
falls quiet once more,

no one can say whether
this spectacular event

will be repeated here in years to come.

The Sardine Run may be unique
to the coast of South Africa,

but it's a vivid reminder of the riches
that our oceans can still support.

The amazing bait balls that characterise
the Sardine Run are short-lived

and very hard to find.

Filming them was to turn
into a two-year mission

for the underwater team.

To film the feeding frenzies,

the team would need three key elements
to come together -

a huge shoal of sardines,
the right mix of predators

and water clear enough to
be able to see the action.

The most important element to start with
was being able to see underwater.

And at the beginning
of the first the season

it wasn't looking good for
underwater cameraman Didier Noirot.

It looks like dirty water, but
I'm going to check anyway to be sure.

ATTENBOROUGH: Didier was
Jacques Cousteau's underwater cameraman

for more than a decade.

He knows that the Sardine Run
is very unpredictable

and that some years
it never happens at all.

The predators were gathering,

but the ocean currents
weren't bringing any sardines.

It wasn't a good start
to the first season's filming.

MAN: What's it like?

No vis. No visibility.

ATTENBOROUGH: And the murky water
held further risks.

Poor vis you don't see what's coming,

so it's not that we're scared
of all the sharks,

but we notice that accidents,
people get bitten always in dirty water.

So why should we take the risk?

We go in dirty water
to make bad pictures

and get bitten by sharks.

It's not worth.

I'd rather stay dry!

ATTENBOROUGH: After 20 days at sea
with no sign of sardines,

the crew kept themselves busy
with some sound recording for the film.

I didn't take my mask, you see,
so I don't intend to dive.

ATTENBOROUGH: The team developed
some ingenious techniques

to get microphones close
to the dolphins and gannets

that were also waiting for the sardines.

So what we're doing today
is trying a radio mic and a Frenchman.

The problem is he doesn't
know when to stop talking.

It's the quietest we've had him
for days, but he still rabbits on.

ATTENBOROUGH: No one was prepared
for what happened next.

The thing is these aren't
waterproof at all.

-Shark, shark! Quick, quick!
-Go, go!

Quick, quick!

He bit me. Big copper.

It's late, it's murky water.
We cannot stay there too long, you see.

-Did he come right underneath you?
-No, he bit my fins. I kick.

-Seriously?
-Yeah, I told you

there are sharks, so come and fetch me.

ATTENBOROUGH:
The sharks were definitely about,

but the first season ended
without Didier seeing any sardines.

At the beginning of the second year
the pressure was on.

But things were looking up.

With the help of aerial spotter
Eric Webber,

Didier and the team
could search a greater stretch of ocean.

For the first time in three years,

a huge slick of fish
had been swept up the coast.

The Sardine Run was well and truly on.

And it was down to the eye in the sky

to get Didier
into the heart of the action.

We've got thousands of sharks
approximately 200 metres offshore.

You guys make your way out there,

you'll be mad enough
to go into the water.

I'll talk you onto it, guys.
It's really looking good.

It's just sharks and sards
all over the place.

We are in the area.

Didier wants us to deploy on
the highest concentration of sharks.

Would you please guide us
onto that area.

Come 20 degrees left, you've got
40 metres to run. 40 metres to run.

I'm going to put you
in the front of the sards.

Seconds to run, divers ready.

Nine, eight, seven, six,

five... Divers ready.

Four, three, two, one.
Go! Divers away.

ATTENBOROUGH: The great tide was indeed
living up to its name.

At last Didier had some action to film.

He had good visibility
and sardines in abundance.

But without dolphins around,

the feeding frenzies
just weren't happening.

The sharks were unable to feed
on the vast walls of fish

and despite their impressive numbers,
they were surprisingly wary of Didier.

No, very quiet, moving slowly.
They are the lords of the sea.

No, there was no frenzy, no attack.

I think they get prepared
for the big action.

ATTENBOROUGH: Didier had yet to even
see a big bait ball

and there was only one week left
for all the elements to come together -

clean water, lots of sardines,
and just the right mix of predators.

And if there was one place
to find it, it was Waterfall Bluff.

Huge numbers of predators
were starting to gather.

This was the most action the underwater
crew had seen in two years,

and again it was down to Eric
to put them on it.

ERIC: This is Raven. Yeah,
we've got some major activity here

just off Mkambati.

ATTENBOROUGH: They were into
the last week of filming

and the pressure was showing.

Yeah, this looks very, very good.

At two o'clock, just here,
but it's moving quite fast.

MAN: 'Cause the dolphins are chasing it.

ERIC: Make a slow 90.
Go right 90 degrees.

The tricky part is
actually getting us onto the bait ball

without breaking it up.

Ridden over the bait ball. Just stop.

ERIC: Joker, I think
you've screwed that up.

Too far! Don't get there.
Move the boat, to the right!

-Below Eric. Below Eric. Where's Eric?
-We should go outside there.

Now we have to go fast
and to think fast!

ATTENBOROUGH:
On the second-to-last day of filming,

Didier finally got his chance.

Okay, Didier.

ATTENBOROUGH: Years of work had gone
into putting Didier on the front line.

Now it was down to him.

After 90 days of filming,

he had less than an hour
in which to fulfil his dream -

to film a bait ball
in perfect conditions.

Didier was at last

amongst the greatest gathering
of predators on the planet.

He'd managed to get closer
than anyone to the feeding frenzy,

without becoming part of it.

Ah! Today was the day.
We just found a bait ball.

We were looking for months, years,

and we finally found it.

Only one problem.
The sharks were too much aggressive.

We were very...
We got bumped a few times by sharks,

and that was just a bit serious.

All that action came and that was
just an amazing spectacle.

All those birds diving together.

Bom, bom, bom. Boom, boom.

Like real cannon explosion.

And all those sharks under, following.

And the dolphins.
That was just magical. Magical.

ATTENBOROUGH: The feeding frenzy
they filmed that day

ended as quickly as it had begun.

After two long years,
Didier and the crew

had managed to be
in just the right place

at just the right time

for one of our ocean's greatest events.

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