All language subtitles for Nature The Oceans Greatest Feast 2022

Viewers like you make
this program possible.

Support your local PBS station.

Alone, a single fish may be insignificant.

But together, they can hold
the fate of an entire coastline.

In the deep, billions of sardines

begin a mass migration...

sparked by a whisper of cool water.

It's the largest movement
of living things on Earth.

And it's about to become
nature's greatest ambush.

Every predator along the coast
is counting on this event...

...to feast on the abundance
the sardines bring...

...before they slip away
into the deep.

Off the southern tip of Africa,

the frigid South Atlantic mixes
with the milder Indian ocean.

The waters are cold and rich
with plankton,

fed by upwellings
from the mighty Atlantic.

Perfect conditions
for a tiny fish to thrive.

Sardines by the billions
live here year-round,

swimming and feeding together
in loose shoals

of hundreds of thousands of individuals.

Then in late April, ocean
currents undergo a subtle shift.

As the southern winter approaches,

upwellings and eddies force
a tendril of cold water

toward the east.

The warm Agulhas Current
moves further offshore,

allowing the cold stream to gain momentum.

The cold-water sardines
instinctively cluster

in the chillier current.

150 miles out to sea,
on the Agulhas Banks,

schools begin to mass together...

...until they form a mega shoal
20 miles long.

Then the single superorganism

pours into the cold-water highway

toward the coast and shallower water.

It's the biggest biomass
migration on the planet,

exceeding the great herds
of the Serengeti.

Yet, exactly why they do it
remains a mystery.

The journey serves no apparent
benefit to the fish.

It will inevitably dead-end in a warm sea,

unsuitable for sardines.

How far they travel
depends entirely on the vagaries

of this year's cold current.

But one thing is certain...

an entire food web is counting
on the sardines to make the run.

Some predators will follow
the shoal for weeks.

Others wait for the feast
to pass close to shore.

Some even race hundreds of miles
to intercept it.

To the multitude, this year's
sardine run can mean

the difference between
abundance and deprivation.

All are at the mercy of the current.

If the water temperature
stays below 70 degrees,

the sardines could travel 1,000 miles

up the Eastern coast of South Africa.

But if the tendril of cold water fades,

the shoals will turn, disperse,
or disappear into the deep.

The coastline waits.

The first hazard for the fish
lies just 100 miles

from the sardine's home turf...

...a colony of some 4,000
Cape fur seals.

They're local predators,

patrolling the shallows close to shore.

The pups need milk every four hours...

...so moms can't go far to hunt.

And they're reluctant to leave the safety

of coastal kelp forests.

The towering plants offer protection

from great white sharks.

If the seals are to feast on sardines,

they need the shoals to come to them.

Mothers depend on the oily fish
to fuel their milk supply.

And they're already pregnant
with next year's baby...

...a precarious position
when your food source is fickle.

The colony is crowded.

Pups cling to mothers.

Tempers fray.

But this year, the sea delivers.

The cold current pushes clouds
of zooplankton

toward the coast and the seal colony.

The little fish follow their food...

...directly into the kelp beds.

For the seals,
it's the moment of the year.

Their front flippers are large
and incredibly powerful.

Like paddles, they propel
the seals at 15 miles per hour.

And they provide control when
maneuverability matters most.

Every seal cooperates.

The seals swallow fish whole...

...even when they're underwater.

In the onslaught, the sardines
school in an ever tighter mass.

It's a proven defense.

Every fish is equipped
with a lateral line...

sensory cells in its head,
trunk, and tail.

It's sensitive enough to pick up
the slightest change

in water pressure.

When a fish feels its neighbor move,

it instantly responds in kind.

Millions of tiny, synchronized
movements combine into one,

forming a superorganism that shape-shifts

and slips just out of reach.

The assault by thousands of hungry seals

barely makes a dent in the giant shoal.

The sardines make their getaway
up the coast,

and the seals don't follow.

They need to get back
to their hungry pups.

The shoal always stays
in the cold current,

covering up to 40 miles a day.

Now the females drop eggs
as they move up the coast...

...prompting some to suggest

that this is an annual spawning run.

Others say it's simply
driven by wind and cold water.

With each mile, the water grows
imperceptibly warmer.

There's no telling where or when,

but the cold current
will eventually dissipate.

For now, it remains strong,
impelling the fish onward.

By early May, the sardines
approach another landmark...

...400 miles east
of the seal colony.

Bird Island.

It's the world's biggest colony
of Cape gannets.

For three months, the birds have been

feeding their growing chicks.

They may be fierce ocean predators,

but they're also devoted parents.

They're monogamous,

always returning to the same nest.

It's crowded.

That means competition for real estate...

and food.

With over 200,000 birds in the colony,

they need 9,000 tons of fish
in one breeding season.

The gannets have pinned
their entire breeding cycle

on the unpredictable arrival of sardines.

Scouts return with full bellies
and good news.

The fish are coming.

The sardine superorganism
is 20 miles offshore...

...within striking distance
of the colony.

The birds appear awkward
on the ground, even comical.

But once they achieve air speed,
they are all grace and danger.

They soar 100 feet in the air.

They scan the shoal
with binocular vision...

...lock on to a target...

...then dive.

Gannets hit the water
at 60 miles per hour.

Muscles lock their
neck vertebrae into place.

Airbags in the face and chest
absorb impact.

The sardines swim deeper to escape,

but the birds' momentum
carries them down...

...30 feet underwater.

If a gannet misses the target,
it holds its breath

and paddles, penguin-like,
for a second grab.

This first hunt is all for the youngsters.

Gannet parents load up their gizzards

and return at high speed to Bird Island.

Every parent knows
exactly where to find its chick.

The food cargo is precious.

A healthy sardine run
means more young gannets

are given a chance to survive.

But this is the fledglings'
last free meal.

The parent birds will leave them
forever and follow the shoals.

Any gannet that wants to eat

must get on the wing and follow the fish.

This is motivation for the chicks to fly.

The hungrier they get,
the harder they try.

The learning curve is steep,

against howling wind and rough seas.

Crash-landing in the waves
is their first pitfall...

...but the wild surf
is not the real danger.

Fur seals hunt these shores, too.

Fledglings don't have
the strength or experience

for a water take-off.

Soaked feathers weigh them down.

Just as the gannets exacted
their toll on the sardines,

the bird colony
now suffers its own losses.

The lucky ones must dry
their feathers and try again.

They can't miss out on the first
sardine hunt of their lives.

The sardines move east
at 6 miles per hour.

They're approaching the first
real crux of their journey.

600 miles into the run,
the coastline bends north,

and the continental shelf
starts to narrow.

Their cold-water ribbon
is pinched against the coast

by warm offshore currents.

Billions of sardines must squeeze

into the cold but narrowing channel.

The shoal is stretched longer and thinner.

The fish pack tighter together.

This current delivers them to
a place called the Wild Coast.

It's a 200-mile stretch...
a pristine, untouched transition

between temperate and tropical biomes.

It's not only a mix of water temperatures,

it's also a crossroads for myriad species.

It's June and humpback whales
pass from Antarctica

to breeding grounds farther north.

Others live here all year round.

50 miles ahead of the shoal,
resident bottlenose dolphins

relish winter's arrival.

Dolphins live in social groups
of about 25 members.

Their play reveals why
they're such formidable hunters.

They're fast, they communicate,

and they move as a unit.

A real-life sardine nemesis.

And this resident pod
is just the advance guard

for an even greater army.

Common dolphins.

They spend most of their lives
in warmer waters

along the coast.

This time of year, their calves
are just beginning to hunt.

Mothers need to wean them before
next spring's breeding season.

A glut of fish would be
a crucial windfall.

There's no guarantee
the sardine run will reach them.

So they come to it.

As they head south, hundreds
of small family pods converge.

A dolphin super pod begins to form,

streaming to intercept the shoal.

100 miles to the south, the fish
pour along the Wild Coast...

unaware of what lies ahead.

As the narrowing current
pushes them to the shallows,

the shoal fragments.

Smaller, isolated bait balls
offer a new opportunity...

for sharks.

These migratory blacktips and dusky sharks

have moved down from
the warmer waters farther north.

Little is known of their lives,

but shark nurseries
have been discovered nearby,

suggesting that the sharks...

like other creatures along the coast...

may time their breeding cycle
to the sardine run.

Tiny fish face off with dozens of sharks.

It seems an unfair match...

but the sardines launch
their schooling defense.

As the sharks move, they send a
pressure wave through the water.

The fish detect it through
their sensitive lateral lines.

Just one moves out of harm's way,

and every fish around it follows.

It's incredibly effective.

The sharks simply can't turn
and bite quick enough.

The predators change tactics.

With sudden bursts of speed,
they try and carve the shoal

into even smaller balls...

...but they just don't
coordinate enough.

A school of 60-pound tuna
gets in on the action.

Normally the sharks hunt tuna,

but they seem to know help
when they see it.

The smaller tuna are much more agile.

Within seconds, they slice
a bait ball from the shoal

and trap it against the surface,

where it's easier for everyone to feed.

Game fish and sharks
enjoy a temporary truce

as they feast on the same prey.

The main shoal flees north,

leaving this fragment behind
to be obliterated.

Even the gulls get their share.

The mega shoal is now way
out of its home habitat.

As long as it's cold,
they swim blindly along.

They're heading toward a feature
of the South African coast

that will prove the most
consequential milestone

of their journey...

a sandstone buttress
called Waterfall Bluff.

This rocky promontory shoves
the cold current eastward

to collide with the warm water
just offshore.

Some years the cold water
can blast beyond this point...

but not this year.

The vital current thins to a trickle.

The sardines follow into
the bottleneck as if spellbound.

Every single fish follows
the same mission...

stick with the school
and stay in the middle.

But in the fading current,

the already fractured shoal
breaks up even further.

Small schools follow shifting
pockets of cool water

into oblivion.

The great journey stalls for the fish

and conditions align for every predator.

A familiar enemy has
trailed them all this way.

Some gannets will fly for 24 hours

to intercept the bottleneck...

and there are plenty more
roosting on the nearby coast.

It's a true test for the rookies.

The sharks are back for more, too.

Until now, the sardines
have managed to slough off

small bait balls as sacrificial decoys.

But now they're more vulnerable
than they've ever been.

The high-flying gannets
are the first to spot

a stalling shoal.

The birds stand out against the sky

like a homing beacon, guiding in an army.

It's the dolphin super pod...

...now grown to 20,000 strong.

The sardines now face
an unprecedented assault

from a fleet
of swift ocean-going hunters...

...and a far-flung deadly
air force assembling above.

The sardines turn
to the only defense they know...

schooling up as tight as they can.

One moves, and they all move.

But the dolphins are prepared for this.

Their goal is to prevent
the shoal from diving deep.

They coordinate their efforts,
blocking the sardines' evasion.

With surgical precision,

they slice balls away from the main shoal.

They blow bubbles to corral any
fish that tries to break form...

...forcing the fish tighter
and tighter together.

Every fish instinctively tries to get

into the middle of the pack.

But now exhausted gills
struggle to suck oxygen

from turbulent water.

Ball after ball is dissected
from the shoal and obliterated.

The dolphins get what they've waited for.

The toll is exponential.

The dolphins are so effective
at herding the fish

that every other predator
is also more successful.

As the fish are driven to the surface,

gannets get easy access.

Dark fledglings now hunt like experts.

Sharks follow and wait
for the perfect moment

to cash in on the tight balls.

They pick off the edges at first...

...then they plough in.

The dolphins are relentless.

Youngsters take the cue and feed
on fish for the first time.

Along miles of coastline,
every predator is synchronized.

Unlikely accomplices
of all stripes work together

toward one brutal goal.

And then, with the fish exhausted

and thousands of predators well fed,

the biggest arrives...

...a 20-ton Bryde's whale.

Thousands of sardines gone
in a single gulp.

The feast goes on for days.

The great shoal is in tatters.

It's now a 3-mile buffet.

Too confused and spent
to reform their shoal,

they're almost 800 miles from home.

They've been duped
by the vanishing current.

Now they're lost and scattered
in a strange, warm ocean...

...simply food for others.

And yet it isn't over.

The predator of all predators arrives.

Orcas.

As smart and cooperative
as a common dolphin

and three times bigger.

Orcas never used to travel
for the sardine run,

but now they swim thousands of
miles to intercept the shoals.

But it's not the sardines they're after.

They're here to hunt dolphins.

Not chasing anymore but running.

The orcas are not only more powerful,

they have more stamina.

Just as the dolphins corralled the fish,

now the orcas work the dolphins.

They isolate one from the pod.

Once they've locked onto
their target, they tag-team...

...chasing it...

...exhausting it...

then... ramming it.

They attack again and again

until the dolphin can no longer swim.

Before they can feast, they drown it.

The orcas have scattered
the dolphin super pod.

Without the organizing force
of the dolphins,

the sardines regroup and
slip away into deep, cold water.

The massive cloud of fish
that dominated the coastline

suddenly vanishes,
as if absorbed by the sea.

As July concludes,
the sated hunters disperse.

Gannets proceed to travel up
to 60 miles a day

searching for more food.

Sharks continue their migrations,

fully fed and stronger for it.

Dolphins have successfully
weaned their calves.

Super pods thin out
as family units regroup

and return to their
regular hunting grounds.

The cold current has delivered the feast

that all the animals were counting on.

Now it fades away, mixing
with the warm Indian Ocean.

Some believe the sardines
ride the current down

to secretly spawn in the deep.

Others say they follow it
all the way back,

1,000 miles to their home off the Cape.

Next year the cold current will reform,

stronger or weaker than the last...

and billions of little fish

will be driven to follow its call,

to face hardship and sacrifice,
toward a purpose yet unknown.