The Rite of Passage (Mała matura 1947)

In the course of making Blue Planet II,

we've explored every corner of the underwater world.

We've encountered extraordinary animals,

and discovered new insights into how life is lived beneath the waves.

For years we thought that the oceans were so vast

and the inhabitants so infinitely numerous

that nothing we could do could have an effect upon them.

But now we know that was wrong.

The oceans are under threat now as never before in human history.

In this final episode,

we will meet the pioneers who are striving to turn things around.

People who are helping to save the ocean's most vulnerable inhabitants

and dedicating their lives to protecting the seas.

But is time running out?

Many people believe that our oceans have reached a crisis point.

So just how fragile is our blue planet?

Winter in the Arctic Circle.

Every year, the waters of Norway are the setting

for one of the greatest wildlife spectacles in the ocean.

Over a billion herring pour into these fields.

The Blue Planet II team spent three years

documenting this astonishing event.

Such a wealth of prey attracts predators

in extraordinary numbers.

Orcas

and humpback whales.

But this migration hasn't always been so bountiful.

Leif Notastad is a Norwegian fisheries scientist.

It's been one of the most important fisheries

that we had for centuries along the whole coast of Norway.

But in the late 1960s

the herrings that we see around us here was on the brink of collapse.

50 years ago, fishing was so intensive

that the herring had all but disappeared.

Orcas were seen as rivals

and hundreds of them were killed.

It was only after the Norwegian government imposed severe restrictions

that the herring began to recover.

Today, this is once again an immensely productive fishery,

closely monitored by teams of scientists.

Marine biologist Eve Jourdain

is one of the resident orca experts.

From 1982, orcas got protected in Norway

and we have clearly one of the largest orca population in the world out here.

There are now over a thousand orcas here.

But with so many mouths to feed, including ours,

can the mistakes of the past be avoided?

To answer this vital question,

Eve and her team are using multi sensor camera tags.

With the tags we try to see how the orcas interact with their prey.

How they hunt and all about the underwater behaviour

that we are not able to see from the boat.

A tag has to be attached

to the orca in exactly the right position.

Here it goes. Here it comes.

Oh, that's a good shot.

It is the least invasive method. It is suction cups.

So it is not a scratch on the whale afterwards

which is something we really like.

While studying the orcas,

Eve noticed a worrying change in their behaviour.

They had worked out the easiest way to get a meal.

We have seen that the orcas are waiting

for those fishing boats to drop the net.

It acts like a dinner bell

and then all the orcas of the area gather.

Quite a lot of herring slip from the net

and this is exactly what the orcas are looking for.

But this new tactic is dangerous, as Eve has witnessed.

We were there to monitor the behaviour of the orcas

scavenging around the nets.

And we realised that one large adult male

was actually trapped inside the net.

When the fishermen started to retrieve the net

the orca was obviously starting to panic

and trying to pull as much as he could.

This orca was really fighting for his life.

Stringent rules require fishermen

to get permission before they open their nets.

But that took time.

It was such a long process.

We thought that the whale was going to die of exhaustion.

Thankfully, the fishermen finally got the clearance

to release their net freeing the exhausted orca.

It was a huge relief to see that this orca made it until the end

and finally got back to his family.

With marine mammals and humans competing so directly

accidents are inevitable.

Two days after tagging an orca,

it's released and Eve collects it.

This tag is full of secrets, you know,

because it has been on the whale for several days

and will just reveal exactly what the whales have been doing.

Pictures from the tag reveal the hunting technique in detail.

They dive below the ball of fish

and then back flip.

The tail slap stuns the herring.

Eve can even work out how many fish the orcas are taking.

They can kill up to 30 herring with just one tail slap.

And then what is pretty amazing is

all the individuals of the group share the dead herring.

And it's not just the orcas feeding here...

Humpback whales are also drawn to the feast.

They too are being tagged and monitored

giving fishery scientist Leif

a complete picture of how much herring is being eaten.

The whales, they take probably less than 1%.

The fishermen take less than 10%.

So the balance there is that there is enough for everybody.

Given that we manage to stock in sustainable

and a long term sustainable way.

But it's estimated that almost a third of ocean fisheries

are being over exploited.

The remarkable recovery of the herring here

demonstrates what can happen if a fishery is carefully managed.

Our maltreatment of the seas has many effects.

Some are predictable,

but there are others that are rather more surprising.

Southeast Asia.

The coral reefs here are among the richest on the planet.

Marine biologist Steve Simpson,

is discovering how important sound is

to the animals that live in these bustling coral cities.

We're only now just realising by listening underwater

that the fish are making all these sounds.

They use sound to attract a mate.

To try and scare away a predator.

You hear pops and grunts and gurgles and snaps.

There's a whole language underwater

that we're only just starting to get a handle on.

Using an advanced multi directional hydrophone,

Steve is trying to make sense of this extraordinary chorus

by working out who is making which noise.

One fish is especially talkative.

It's perhaps the reef's most famous resident.

The clownfish.

While filming for the series,

we followed this particular family of saddleback clownfish

as they search for a suitable place to lay their eggs.

It's a noisy affair.

For clownfish sound really is everything.

They spend all day talking to each other.

You've got dominance and submission.

You've got all the others calling to each other.

It seems that they also use sound

in protecting themselves from the many predators that hunt around the reef.

Including coral trout.

Will this model trout fool the clownfish?

They react almost immediately.

By mimicking a predator,

Steve manages to record their alarm calls without putting them at risk.

You can really hear the deeper pulsing sound of the female

as she tries to scare the coral trout away.

And all the little ones are just popping... Pop, pop, pop.

As if to say, "I'm still okay. I'm still alive."

So they've got this real language of sounds that they're using

just to try and defend the colony against this coral trout.

But that discovery has led to a serious worry.

The fish were really popping away at the predator.

But as soon as the boat came over they looked completely distracted.

With all that noise it completely changed how the fish were behaving.

Unable to make themselves heard above the noise of boats,

the family can't warn each other of danger.

And so they are now vulnerable to attack.

You think about how many boats are driving around.

All of the ships, all of the offshore drilling.

All the noise that we're making in the ocean

you realise just how much we're drowning out

this natural biological noise,

robbing animals of their ability to be able to talk to each other.

All this noise may have serious consequences for many reef fish

because their babies, as soon as they hatch are swept out to sea.

There they feed and grow until strong enough to swim back.

And to find the reef, they use sound.

They listen in. They eavesdrop to the noises that they can hear

and they use that to choose which reef they want to make their home.

But obviously because we're adding all this noise to the ocean

it's a wonder whether they can even hear the reef at all.

Man-made noise is now everywhere in the ocean.

And it has an effect on marine creatures of all kinds.

From tiny fish

to gigantic whales.

But Steve believes there are solutions.

Noise in the ocean is a real problem.

But, it's something that we can control.

We can choose where we make the noise.

We can choose when we make the noise.

We can directly reduce the amount of noise that we make

and we can start doing that today.

We're only now beginning to realise

what an impact our noise is having on the inhabitants of the ocean.

Other forms of pollution are only too familiar.

Since its invention some hundred years ago,

plastic has become an integral part of our daily lives.

But every year, some eight million tons of it

ends up in the ocean.

And there, it could be lethal.

While filming Blue Planet II,

the crews found plastic in every ocean.

Even in the most remote locations.