The South Pacific is, on the face of it, still a healthy ocean.
We depend on it.
Over 60% of the world's fish catch comes from the Pacific.
But like all oceans,
it has little or no protection,
so it may not stay healthy much longer.
So what's being done to preserve its natural treasures?
And what does the future hold for this fragile paradise?
For the South Pacific, this is a critical time.
It's changing in ways that, if left unchecked,
could develop into a global crisis.
Some of its residents have been through crisis before.
Humpback whales were hunted so relentlessly during the last century
that their numbers crashed by 90%.
But recently, they've made a comeback,
surging from 5,000 to 60,000 animals.
Their blubber is no longer boiled down for oil.
Today, these whales are greeted by boats loaded not with harpoons,
but with tourists.
The waters of Tonga are one of the few places in the world
where it's legal to get in and meet the giants face to face.
Some claim that to look into the eye of a whale
is a life-changing experience.
In the 1970s, a campaign to "Save the Whale"
made the headlines around the world,
and led to an unprecedented agreement
to protect what remained of the world's whales.
It proved that global pressure CAN save wildlife that's under threat.
So what are the current threats to wildlife in the Pacific?
It's no secret that the world is getting warmer.
And the low-lying islands of the South Pacific are on the front line,
as global warming causes sea levels to rise.
On the Pacific island nation of Tuvalu,
nowhere is higher than five metres above sea level.
Tuvalu's nine atolls and islands are home to 12,000 people.
Their contribution to global warming is tiny,
but its impact on them is massive.
Sea walls are the nation's only defence,
but building higher walls is likely to prove futile.
During big spring tides,
seawater simply bubbles up through the ground.
In 2006, the islanders experienced their highest tides ever.
These islands could soon become uninhabitable.
The seawater is poisoning the soil and groundwater.
Eventually, the islands may have to be evacuated.
This would be an unprecedented move...
An entire nation relocated.
So the ocean is threatening its islands,
thanks to global warming.
And yet, the Pacific is playing a massive part
in slowing down climate change.
The world's oceans have absorbed about half of all the carbon dioxide
released so far into the atmosphere by industry,
significantly reducing the greenhouse effect.
But there's a catch...
For the fish, all that extra carbon dioxide in the water
can have some unwanted side effects.
All life in the Pacific is dependent on the tiniest of creatures -
the plankton that floats freely in the currents.
One of the most plentiful is the sea butterfly,
a tiny marine snail, which uses its enlarged foot
to fly through the water.
Sea butterflies are such important food for so many marine animals
they have been dubbed the "potato chips of the ocean".
But they could be under threat from all that extra carbon dioxide.
Dissolved carbon dioxide is slowly turning the water more acidic,
making it harder for sea butterflies to build their calcium shells.
The loss of these swimming "potato chips"
would have repercussions right up the food chain.
And with a billion people around the world
dependent on fish for their protein,
fewer fish would clearly be bad news for people too.
Of course, there's no need to worry,
if the greenhouse gases are brought under control.
Or is there?
Although the burning of fossil fuels
is often viewed as the biggest environmental threat,
here in the Pacific there are more pressing concerns.
The fish may disappear
long before the impact of climate change really takes hold.
A leading group of ecologists recently predicted
that in just 40 years, seafood will be off the menu.
The problem has a lot to do with fishing.
In Fiji, the villagers of Moturiki Island are fishing for dinner.
Using a traditional fishing technique known as a fish drive,
they work together to scare the fish off the reef
and into an ever-smaller corral.
Each year, in coastal waters around the Pacific's islands,
subsistence fishermen catch around 80,000 tonnes of fish.
In the past, there was always plenty more fish in the sea,
but recently, catches have been declining.
Why should this be?
It could be that more efficient fishing gear,
such as modern nylon nets coupled with growing island populations,
has led to over-fishing.
But catching too many fish
may not be the main reason why there are now too few.
Pacific coastal fish live and breed in the most fragile of habitats -
coral reefs.
But many reefs have been trampled on, smashed by boats,
and even dynamited in the quest for fish.
And damaged reefs support fewer fish.
This could be why the fishermen are catching less.
In Fiji, biologists are working with fishermen
to bring the fish back by replanting the reefs.
This is a coral nursery.
But with wild corals already struggling,
where have these coral seedlings come from?
The coral gardeners monitor the reef,
looking for corals that need a helping hand.
Despite all this real estate, many corals end up clustered together.
Crowded out, they will eventually die,
so the gardeners uproot them, creating more space for some,
and giving the uprooted ones a fresh start.
Each coral head is broken down into a dozen or more fingers
and each of these is tied onto a concrete disc.
As every gardener knows, vigorous growth requires sunlight,
plenty of nutrients and the right temperature.
So the coral gardeners choose just the spot.
Within six months, the corals are branching out.
They're spaced out onto adjacent tables
and, a year or two after planting, they're ready for harvesting.
The coral heads are broken down once more.
In the space of two years, a single finger of coral
has multiplied into 50 or more.
Some of these will be re-planted on fresh discs,
while others will be returned to the reef.
If replicated, coral gardening could help
restore reefs throughout the Pacific.
But its biggest success
may be in sowing the seeds of conservation in the local fishermen.
Within days, these cuttings will have stuck themselves to the reef,
while reefs that were replanted a year ago
are already starting to bloom.
In a few more years, this area should be awash with fish.
So there's hope for coastal fisheries on which local people depend.
Out in the open ocean, it's another story.
There is no protection here,
and yet this is where most fish are now being caught.
These may look like minnows, but they are tuna,
each a healthy two kilos or more.
Four different species are fished in the tropical Pacific.
These are skipjack tuna,
with some yellowfin tuna mixed in.
But this boat is not setting nets.
The ancient technique of fishing with rod and line
is now practised on an industrial scale.
The water jets break up the outline of the boat from below,
and mimic the noise and commotion of baitfish when under attack.
Meanwhile, live baitfish are strewn around the boat
to keep the tuna interested.
It may look like a lot of effort for a few fish,
but this pole and line technique of fishing can be surprisingly effective.
Fishing for export is now big business in the tropical Pacific,
with tuna alone accounting for 30 times more fish
than all the fish caught by subsistence fishermen.
So is commercial fishing sustainable?
Skipjack are the smallest,
and by far the most abundant tuna species in the Pacific.
They reach maturity in just a year
and then spawn many times within a season.
They seem to be the perfect catch,
as their numbers just keep bouncing back.
But not all marine life is so resilient.
Thanks to modern fishing,
some of the best-known animals of the Pacific are in deep trouble.
Sharks have been top dog in the Pacific for millions of years.
They control the numbers of other fish,
and so play a vital role
in keeping the underwater ecosystem healthy and diverse.
In French Polynesia, grey reef sharks gather.
While scalloped hammerheads patrol the Galápagos Islands,
these are rare hot spots where sharks converge in large numbers.
But divers claim this is just a fraction
of the number of sharks they used to see.
Many sharks are ocean migrants,
travelling hundreds of miles in search of prey,
like the oceanic whitetip.
Amazingly, this may once have been
the most abundant large animal on the planet.
But it's fallen prey to fishermen's hooks and nets.
Surveys suggest oceanic whitetips may have declined
by a staggering 99%.
It's like the disappearance of bison from America's Great Plains,
yet it's only happened in the past 50 years,
and almost no-one has noticed.
Incredibly, the world's oceans may have lost more than 90%
of their large predatory fish since industrialised fishing began.
Tiger sharks still turn up in Hawaiian waters,
drawn here by another great ocean wanderer.
These black-footed albatross are certainly an endangered species,
but not because of the sharks.
Thousands of adult black-footed albatross are caught each year on fishing lines.
In fact, 19 of the world's 22 species of albatross
are endangered or vulnerable to extinction,
largely thanks to fishing.
The Antipodean, or wandering albatross
is found in the waters around New Zealand,
home to the most diverse seabird community in the world.
These are rich fishing grounds for fishermen too.
The birds know that where there are fishermen,
a free lunch is sure to follow.
So how does this get them into trouble?
With a wingspan over three metres, an albatross is built to soar
thousands of miles across the ocean in its quest for food.
As it might go for days with nothing,
it can't afford to be choosy.
Anything near the surface is snapped up.
Unfortunately, not everything a fisherman casts overboard
is a healthy meal.
Far out at sea, a long-line fishing vessel is setting its line.
It's long-line vessels in particular that have been held responsible
for the decline of the albatross.
The fishermen pay out a line 30 miles long
across the surface of the ocean,
and every few metres, they attach a secondary line
with a hook, baited with a fish or squid.
Every night, this vessel casts over 1,000 hooks,
and it is just one of many long-liners plying the Pacific,
some with lines 100 miles long.
But this fisherman is well aware of the threat to the seabirds,
and to prevent them from swallowing his hooks,
he has adopted bird-friendly fishing methods.
It's why he sets his lines at night, when the albatross are sleeping.
And he deploys tori lines.
These simple streamers are remarkably effective
at scaring birds away from the hooks.
He also thaws out his bait before hooking it,
so it sinks out of sight quickly.
His bird catch is now virtually zero.
This leaves more hooks free for his target species - bigeye tuna.
These are powerful fish, and can weigh well over 100 kilos.
It may look brutal, but the most humane way to kill one quickly
is to shoot it.
The future of the albatross still hangs in the balance.
The birds around New Zealand are benefiting from a law that states
all long-line fishing vessels must use bird-friendly methods.
But albatross are great travellers,
so they're still at risk throughout the rest of the South Pacific.
Only if all fishing vessels adopt the same bird-friendly techniques
will the story of the albatross -
like that of the whale - have a happy ending.
Saving sharks is not so straightforward.
They're not just caught accidentally -
their fins are worth a fortune,
thanks to an Oriental taste for shark-fin soup.
Over 70 million sharks are killed every year,
many in the South Pacific, where shark finning is neither outlawed
nor properly regulated.
This is a bigeye thresher,
a shark that's almost never been seen in the wild.
Shark finning is a wasteful and often cruel practice,
and one that may ultimately disrupt the balance of life in the ocean,
proving catastrophic for other marine life too.
So how can sharks be saved?
In Bega Lagoon, in Fiji, the local people are proving
that sharks can be more valuable alive than dead.
Tourists will pay good money for an encounter with real live sharks.
This is a community-owned reef,
and some of the money goes to the local villagers -
a big incentive not to kill the main attraction.
Fijians have long had an affinity with sharks.
Their ancestors worshipped a shark god,
who they believed kept them safe from harm.
They would feed sharks, not hunt them,
and these divers continue the tradition.
First to the feast are tawny nurse sharks.
But these sharks are scavengers.
It's the big predators the tourists want to see.
Bull sharks.
Growing up to three-and-a-half metres long,
these sharks are one of the ocean's top predators,
with an aggressive reputation.
The chief shark feeder
is from a village where the shark god is still worshiped.
So he has no fear.
A bowl of shark-fin soup can sell for over 100 dollars,
but here, each tourist pays that to see these sharks alive,
and dives take place several times each week.
To protect the sharks, this reef has now been declared a marine reserve...
...with the added bonus that other fish are protected too.
Before the reserve was established, this reef had been fished-out.
Even a single giant trevally of this size was a rarity.
Today, the divers are in for a special treat.
A five-metre tiger shark.
The dive leaders have named her Scarface.
She turns up once a month or so.
She's inquisitive, but not aggressive.
The show's over.
The divers have had a great day, and local people benefit too.
With so many fish, some spill over into the waters beyond the reserve,
where fishermen now catch many more
than they did before the reserve was set up.
Marine reserves clearly work.
So why aren't there more of them?
In truth, marine protection is decades behind wildlife protection on land.
Take the islands of New Zealand.
Beyond the farmed landscape are wild places where nature can flourish.
More than a quarter of the country is set aside
in national parks and other reserves.
In contrast, less than 1% of the Pacific Ocean is protected.
Instead, it is divided up into fishing zones.
Each island nation owns the fishing rights up to 200 miles offshore.
Beyond these territorial waters are the so-called "high seas".
Bounded by national waters,
the high seas pockets of the western Pacific
cover half a million square miles.
The surrounding island nations would like these pockets
to be declared marine reserves -
safe havens where migratory fish can breed.
The idea is being promoted by Greenpeace.
Greenpeace made their name campaigning to save the whales.
They're now responding to concerns
about the future of the Pacific's fish.
The high seas pockets they're now patrolling
were once a fishing free-for-all.
Although now regulated by international treaty,
they are rarely policed,
so Greenpeace have assigned a monitoring role to themselves.
This is the Esperanza -
Greenpeace's largest vessel.
The crew are searching for any sign of fishing activity
but it's a huge area.
After two weeks at sea, a blip on the radar indicates
a fishing vessel is near.
Greenpeace want to discover
where the vessel is from and what it's been catching.
They launch their inflatable boats.
Although Greenpeace film their own activities,
we put our cameraman on board to ensure an unbiased record of events.
As these are international waters, any nation can fish here legally,
and many do, including the US,
the European Union, Japan and other East Asian countries.
This is a large Taiwanese long-liner.
Taiwan has a large fishing fleet, with many vessels fishing
almost exclusively in international waters.
The encounter turns out to be entirely amicable.
Visitors are rare for fishermen on the high seas,
and these men are not aware that they have anything to hide.
Greenpeace ask if they can inspect the vessel's catch
and the fishermen oblige.
In a freezer, there are several dozen frozen sharks
but the valuable parts are being stored elsewhere.
The shark fin, what do you...?
- Do you sell them in Taiwan too? - No, no.
In another freezer are a dozen sacks of shark fins.
The fins from hundreds of sharks.
By documenting these catches, Greenpeace hope to highlight
why it's necessary to declare these high sea pockets marine reserves,
and to back the growing movement from Pacific Islanders for protection.
This would help to protect all ocean life,
especially the valuable tuna.
Tuna are predators.
They herd smaller fish to the surface, where they can be picked off one by one.
They are high-speed fish - the cheetahs of the ocean.
They're also the wildebeest - they herd together in their thousands
and undertake epic migrations across the Pacific in search of their prey.
If these animals lived on land,
they'd be famous for providing the greatest wildlife spectacle on Earth.
Instead, they're better known as a filling for a sandwich.
In an ocean with no marine reserves, migratory fish have nowhere to hide.
Up to 2 kilometres long and 200 metres deep,
"purse seine" nets are designed to encircle schools of tuna.
A fisherman checks his nets, breathing air pumped down a tube
from the vessel above.
It's not only tuna that get caught in these nets.
A lone turtle was in the wrong place at the wrong time.
She can only hold her breath for a few minutes
and the path to the surface isn't clear.
She begins to panic.
These fishermen are superstitious about turtles.
Bringing one on board
is bad luck.
It's her lucky day.
More and more fishing vessels are being drawn
to the South Pacific each year, as this is one of the last oceans
where healthy numbers of fish still remain.
But for how much longer?
Fishing is now a high-tech operation, with radar picking up
distant flocks of birds that indicate fish feeding below.
The net is paid out in a wide circle around the fish.
It's a race against time, as the fish could disappear at any moment.
As the circle closes, pellets of dye are dropped into the water.
The dye, and the speedboats overhead,
discourage the tuna from making a dash through the closing gap
in the wall of net.
As the net closes,
a draw-cord running along the bottom of the net is pulled tight.
The net becomes a bag, or "purse", and the fish are trapped.
There are 150 tonnes of fish in this one haul.
It used to take a fishing vessel one whole year to catch this many fish.
These are mostly yellowfin tuna, plus some skipjack.
As they're slower breeders than skipjack,
many yellowfin are caught before they're old enough to breed.
This makes them more vulnerable to over-fishing.
Tuna fishing has grown into an eight-billion dollar industry.
And over four million tonnes of tuna are caught worldwide each year,
a four-fold increase in as many decades.
Almost two-thirds of the catch now comes from the Pacific.
In the Atlantic, yellowfin catches have been shrinking since 1990.
Now a similar decline has begun in the Pacific.
Tuna need to swim constantly
to keep water flowing over their gills, otherwise they can't breathe.
The fishermen want to get them out of the water as quickly as possible.
When starved of oxygen, a build-up of lactic acid in their muscles
causes the quality of their meat to deteriorate.
The fish are scooped up from the water, a tonne or two at a time.
Every last fish from this school
of 7,000 yellowfin and skipjack tuna is plucked from the water.
With fishing techniques now so efficient,
and with ever more vessels plying the Pacific,
there is real concern among biologists
that even the resilient skipjack may begin to decline.
This vessel is not one of the newcomers.
It's a Papua New Guinea-flagged ship, fishing in their territorial waters.
So it is subject to catch limits
and regulations that are amongst the strictest in the Pacific,
designed to ensure that tuna fishing remains sustainable.
But New Guinea's fishermen are concerned about the increasing numbers
of foreign vessels now fishing for Pacific tuna.
They were the first nation to propose
that the high seas pockets beyond their national waters
be declared marine reserves, as now advocated by Greenpeace.
After our cameraman left the Esperanza,
Greenpeace continued their journey,
and captured these images of the world's biggest purse seiner,
with a capacity almost four times larger than the New Guinea vessel.
It's a Spanish ship fishing for Pacific tuna
to stock European supermarkets.
The presence of such large vessels,
from countries that have already over-fished their own tuna stocks,
has riled the operators of local fishing fleets,
perhaps with some justification.
Some biologists have recently warned that tuna populations in the Pacific
will be crashing within five years unless urgent action is taken.
Perhaps it's time to think again about the ways we fish.
These pole and line fishermen are Solomon Islanders,
and this fishing is a local industry.
They target specific species, and mature individuals.
There's almost no by-catch - no seabirds, no sharks.
And they can be selective - flicking juvenile fish off their hooks
so they can grow and breed.
Because it's impossible to hook every last fish in a school,
some are always left to fight another day.
And since the fish don't suffer for hours in nets,
this meat is of a high quality.
These fishermen may not catch as many fish as a purse seiner,
but then, that's the point.
Whether any fishing is sustainable
depends on how many fish are caught, how many are left to breed
and how many other species are caught by accident.
But these fishermen may have got it about right.
The Marine Stewardship Council assesses the environmental impacts
of the world's fisheries, and they believe
that pole and line fisheries have the potential
to be approved as officially sustainable.
So now it's down to us, the fish-eaters.
It may cost a few pennies more
to buy a tin of tuna labelled "sustainably caught",
but it could ensure future generations can also enjoy a tuna sandwich,
tuna steak or sashimi.
And protecting the fish will ensure a healthy ocean
for all the marine life of the Pacific.
It will require international commitment and co-operation,
but the whales are a reminder that it can be done.
For the whales, for the fish, and for ourselves,
the way we harvest the Pacific is key to protecting this fragile ocean paradise.
To film the purse seine fishing sequence,
the South Pacific team decided they would need to put a cameraman
inside the fishing net.
Few divers have ever attempted this before.
And it proved to be a real challenge.
To be in the right spot at the right time,
the film crew must take up residence on a purse seine vessel.
This 60-metre Papua New Guinea vessel can hold 800 tonnes of fish.
For the 30-strong, all-male crew this boat is home.
They spend 330 days of the year at sea,
and can go two years without seeing their families.
Their lives are a never-ending quest for fish.
They're in port for three days,
which gives the film crew a chance
to jump on board.
Here we are.
It's a vast ocean,
and even the fishermen don't know where the fish are,
so they set a course for the location of their last big catch.
The film crew have arranged for a dive boat to meet them there.
Without the support of a professional dive boat,
it would be dangerous to get in the water and film.
Just hours after leaving, reports come in of big tuna catches up north,
and the captain sets a new course.
This is not good news for the team.
Our dive boat is based out of here...
and we're gonna be up here.
For the dive boat, that would be about 45 hours.
This new location is well out of range of the dive boat.
With the success of the shoot hinging on the diving,
this is a worrying turn of events.
The fishing boat motors on all night, taking the team
further and further from their planned rendezvous.
Our position now is three degrees...
Eventually, the crew make contact with a passing fishing boat,
and it's heading back in the direction of their dive boat.
There is another boat out here,
which is going on a much better course, so we're gonna transfer.
It's a lucky escape for the team.
The new vessel spends all day and all night
motoring towards the new fishing grounds.
8.28 in the morning, and we've already discovered fish.
Right out there, about 150 metres,
the sea is frothing and boiling
and that's obviously where the tuna are,
so the ship is doing a circle round it and that's where they'll set the nets.
It's all on, it's all on.
Although it's a relief to begin filming,
the real challenge is still to come.
They need to get inside the net,
and right now, that's not a very inviting prospect.
But first, they need their dive boat to find them in this vast expanse.
I can see our dive boat on the horizon, she's a little speck in the distance.
Here we ago again, ship transfer.
There you go, that's our new home.
See you tomorrow.
At five in the morning, the fishermen are already setting the nets.
It's time to take the plunge.
It may seem a little strange
why we're putting fishing net on our scuba gear,
but it has a very useful purpose. These jagged edges of the gear
are completely covered with this fishing net
to prevent us from getting snagged and caught like fish.
I don't normally wear a knife this big, but in this kind of situation,
with all the nets around and possibility of entanglement,
it's a really good idea.
This is a shark shield, and with a tuna-fishing boat,
thousands of bloody tuna in the water,
and a sea full of sharks, it could come in very handy.
They enter the net.
Despite having done all they can to prepare,
this is a jump into the unknown.
The scale of the net is breathtaking.
They're relieved to find that there are no sharks this time.
But there are also no fish.
Frustratingly, days pass
and the fishermen fail to find any more fish.
We're going down to the wire here.
We've got two days left and we still haven't seen any fish,
so getting a little nervous.
Yeah, it'd be tragic to be out here and not have the opportunity to film this.
Eventually, they locate a school.
So the question is, are there any fish in that net?
This is the team's last chance to get the sequence.
To their great relief, all their effort has finally paid off.
They share the net with 150 tonnes of tuna -
one of the biggest catches of the year.
It's an intense experience.
Once again, there are no sharks.
But as the net tightens, the space inside gets ever smaller.
The fish begin to panic.
Eventually, the crew have to bail out.
They continue to film from outside the net.
The filming has been a success,
but seeing death on this scale has quite an impact on the team.
Speechless, really.
It was...unbelievable.
Really. It's hard to find words to describe that.
At first you got in, it was just empty, there's just that serene silence, that...
Turn around, and all of a sudden, this whole space is filled with fish,
just frenetic, fast-moving fish just going crazy.
From then on in, it was just absolutely intense.
You don't know which is up or down or side.
Your whole frame of reference goes off.
And finally, the net was the one static point, wasn't it?
At the start of the dive, you feel like the net
is something to keep away from, but by the end of the dive
the net is the only thing you can use as a frame of reference
and everything else is just moving, and it's very disorientating.
And there were other surprises.
The slick of blood that comes from this is just, like, pouring out of the net
in this massive slick, and you would have thought in this ocean
it would have attracted hundreds of sharks,
but I didn't see a single one, not one shark.
It's a worrying sign that all is not well in the South Pacific.
So what of the fish?
What we saw today was a highly unique experience
and I think it does make you wonder what our impact on the oceans are
when you see it first-hand like that.
The team were lucky.
With so many vessels now fishing throughout the Pacific,
it may not be possible to film scenes like these for very much longer.