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(suspensefull music)

- [Gabriel] In the North Atlantic and the great rivers

that pour into it, there is a legendary fish

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whose future is now on the brink.

The Atlantic salmon.

It travels thousands of miles from river to sea,

facing great risks and then returning back again.

- There's something very special about the salmon.

It's homing to its place of its birth.

- [Gabriel] Once salmon leave the streams of their birth,

they live a phantom, unknown life at sea.

Magically they reappear some years later,

called back to the very river where they were born.

Whole communities once flourished

on this bounty from the sea,

but now something mysterious

and deadly is happening to them.

- We know that we send out a lot of smolts to sea each year

and they're just not coming back.

- This is my way of life, it's my family's way of life,

and it's part of the fabric of Scotland,

and you know, we want it to continue

for many generations to come.

- [Gabriel] Somewhere on the salmon's epic journey,

these remarkable fish are now dying in huge numbers.

- There's a mystery of smolts either not coming back,

and it's very important to understand

where this mortality is occurring.

- [Gabriel] In the last 30 years, returning populations

of wild Atlantic salmon have dropped by 70%.

To save these salmon, first we must find out

what is happening to them.

For some, the problem is clear.

- Principally, the problem is that we have been killing

too many fish for too long.

Government and scientists don't accept it,

they don't recognize it.

- [Gabriel] Others believe there's more to understand.

- The ocean's really a big unknown for salmon.

We have these big picture ideas of what goes on,

but we really don't know any of the details.

- I just implore anyone

that can influence what's going on at sea to do so.

Pick up that ball and run with it.

- [Gabriel] With livelihoods at stake,

and a natural wonder in danger of vanishing,

now scientific detectives race to solve the mystery,

and for the first time ever,

an international team heads out into the North Atlantic

to find why the wild Atlantic salmon is lost at sea.

(dramatic music)

Our relationship with salmon is ancient and powerful.

The oldest known image of one is carved 25,000 years ago

on the ceiling of a cave in France.

The Romans when they invaded northern Europe

marveled at its acrobatics

and called it salar from the Latin saliere, the leaper.

Standing stones carved with its image

are one of the few remnants that an ancient people,

the Picts, left behind over 1000 years ago.

- We're here at Glamis in the precincts of the Kirk,

and here next to me is the great Glamis stone,

which is world famous,

largely because of this etched salmon,

wild Atlantic salmon.

Now this was probably carved by a Pictish engraver

about 12 to 1300 years ago.

The Picts were here in Scotland in the seventh,

eighth, and ninth centuries,

and their culture focused on the natural environment

in a very special way.

If you look above the salmon,

you'll see what people, I think incorrectly,

describe as a serpent.

I don't think it's a serpent at all,

I think it's an eel.

And the thing about the eel and the salmon

is that both migrate.

They're fish that cross human boundaries.

They're fish that pay no attention to political frontiers.

They travel the oceans, the eels as we know

go to the Sargasso Sea to spawn

and where their young are born and then they come back,

and the salmon come here, and they spawn,

and then the small fish go to sea to get big.

So this sense of the community based culture

attributing to these remarkable animals

an almost mystical sense of wisdom and understanding

which they themselves were unable to grasp.

- [Gabriel] For millennia, around the North Atlantic,

people awaited the annual return of the great fish.

In Ireland and Scotland, the salmon fishery

was a way of life.

It fed whole communities.

The ancient fishing village of Claddagh

at the mouth of Galway Bay in the west of Ireland

dates to pre-Christian times,

and so valued were the fish to the town of Galway

that a watchtower was built in the mid-1800s

to announce the return of the salmon to the Corrib River.

Salmon not only filled stomachs, it fed dreams.

Taking this great fish on a gossamer line

was soon a lifetime's thrill.

Upper classes embraced a new sport

and great estates flourished.

Here in the heart of Scotland, salmon angling was born.

Fishing the wide Spey river required its own rules.

A custom fly rod and a unique cast

to reach pools where the great fish, fresh from the sea,

had gathered.

- My family has run and owned and organized fishing here

for centuries, not just decades,

and my children have caught their first fish on the river.

I could show you the point where everyone

caught their first salmon, it's an iconic moment.

- [Gabriel] 20 years ago, as many as 3000 salmon were taken

on this stretch of river.

Today, catches are now less than 1000.

- The fish are no longer there,

and it's gone from harvesting a surplus

to worrying about whether there are any fish at all.

The local economy is massively influenced

by what goes on in this river.

And even in the best of days,

it can be quite an elusive salmon,

but at the moment it's particularly elusive.

- Good luck, I'll see you a few more years.

(laughs)

- [Gabriel] On both sides of the Atlantic,

great salmon rivers are losing their fish.

In the late 1800s a daughter of Queen Victoria

and her husband the Governor General of Canada

came to the Grand Cascapedia,

bringing the sport of salmon angling across the Atlantic.

The river teemed.

Soon dignitaries and tycoons were attracted

to this beautiful, remote area,

for some of the largest of the species came to this river.

But that was over a century ago, and much has changed.

On the great fishing rivers all around the Atlantic rim,

salmon are disappearing fast.

In the last two decades, some new unknown disaster

has emerged.

Somewhere on the journey between

young salmon heading out to sea

and adults returning to spawn

their numbers are being decimated.

For scientists, the race is on to find the cause,

but if they fail, this magnificent creature

may soon be gone.

- We had a recent, massive decline in the return rates

of wild Atlantic salmon from the ocean to the rivers,

and the key is to find out where and when

the mortality is occurring

that is causing the salmon to decline.

Right now I must admit I'm totally flummoxed.

- Over the course of all the different environments

and over the course of the life cycle of the salmon,

there's a lot of different threats

that can be impacting its productivity.

A wide range of things are happening

in the fresh water side.

In the ocean, salmon are dying in the ocean

at relatively high rates,

higher rates than we've seen prior, and we don't know why.

- [Gabriel] But today, researchers are tracking salmon

at every stage of their remarkable life's journey.

The many thousand mile migration

from river to sea and back again.

It's a challenging journey of discovery.

Salmon evolved in the ocean,

and for millennia, this was their home.

Their life in rivers began after the last ice age,

when huge glaciers and sheets of ice

covered much of the northern hemisphere.

And when the Earth warmed, the ice started to melt.

As the glaciers retreated, they gouged out the earth,

causing deep trenches that turned into rivers.

One of the first fish to colonize these new cold rivers

was the Arctic chard, a close relative of the salmon.

They still thrive in the Arctic today.

As the ice retreated, ancestral salmon

pioneered new rivers all over the North Atlantic,

safe havens to lay their eggs.

Over time they adapted to each river

as a genetically distinct population,

and today, no two rivers

hold the exact same genetic strain of salmon.

(serene music)

In a clear, protected stream, buried in the gravel,

are salmon eggs.

This is where life begins.

It is now early spring and the eggs are hatching.

Less than 1% of these eggs will survive

to make their way to the sea.

These newborns remain in their rocky nest

for up to 12 weeks.

Once they have consumed their surrounding egg sacks,

they are ready for the next chapter of their lives.

Feeding voraciously on microscopic life.

Within a few months, they are transformed

with distinct markings to help them blend in with the river.

They dart up to the surface to catch a variety of insects.

They will remain in the rivers for one to six years,

preparing themselves for the next stage.

They take their cue in part from water temperature.

When warm enough, they set off downstream

on the great journey to the sea.

This is where the mystery starts.

On the River Finn in Ireland,

biologist Art Niven and his team monitor the juveniles.

A low level pulse of electricity

temporarily stuns any fish,

allow the scientists to count them.

- We conduct a program,

an annual program during the summer months

of electrofishing to collect the juvenile fish,

and we can look at their age class and their age structures,

and we then release these fish alive back into the river,

so it vies us a unique opportunity

to have a snapshot to see the health

of the juvenile populations within the river at that time.

We also monitor the chemical water quality.

We collect water samples in a bottle

and take them back to our own laboratory for analysis.

- [Gabriel] Art and his colleagues

have found the river is healthy,

with an abundance of youngsters.

An extraordinary transformation is happening

in rivers and streams each spring.

Juvenile salmon are growing into what is known as smolts.

Their bodies are becoming streamlined

for long distance travel,

and their coats are turning silver,

camouflage for life at sea.

Until recently, no one knew their fate from this point on.

On the far side of the Atlantic in Canada,

some young fish are about to encounter

this ingenious device.

A smolt wheel.

As the wheel turns, passing fish are trapped inside.

Biologist Jonathan Carr of the Atlantic Salmon Federation

inserts an acoustic tag in a fish.

As they pass receivers placed downstream,

they emit a ping that identifies each individual fish

by a number, thus allowing the biologists

to determine how many are making it downriver,

into the estuary, and beyond.

- These are the type of receivers we put out,

so as a fish is swimming by with one of these tags,

the receiver will pick up the signal

and record right down to the second

that this fish moved by and the tag ID

to basically cover the width of the river

so that we know exactly when the fish is moving by.

- [Gabriel] Jonathan has tagged 40 fish today.

The next day he heads downstream

to the mouth of the Cascapedia

to check the acoustic receivers.

- It tells on the side of the screen here,

39 out of 40 fish gone by this unit.

Pretty good information.

Most of them made it out.

Some of these fish, after release it only took

a matter of one to two hours

before they reached this point.

And the release site was about 10 kilometers,

so these guys are moving pretty fast.

- [Gabriel] So far, numbers are reassuringly high,

indicating that the real dangers lie elsewhere.

But on the nearby Miramichi River

young fish are under attack by a new predator.

Once protected, the striped bass population

has recently exploded.

Huge numbers of these voracious predators

spawn in the Miramichi Bay

just as the young salmon are heading to sea.

(suspenseful music)

They don't stand a chance.

Across the Atlantic, warming seas lure southern fish

such as the striped bass to northern waters.

Another challenge.

Acoustic receivers tell us that only

three out of 10 young fish survive the Miramichi

and make it past the striped bass

and into the Gulf of St. Lawrence.

But on the Cascapedia, only 250 kilometers to the north,

there are no spawning striped bass

and fully eight out of 10 survive.

Farther out, the next set of receivers

tells us that only 50% of adult salmon

that have already spawned and are returning to sea

make it out of the Gulf of St. Lawrence.

This is an ominous sign.

Biologists know that 25% are being eaten by predators,

but they don't know what is happening to the rest.

Scientists haven't yet been bale to verify

how many of the young make it into the ocean.

The survivors are now ready for the estuary,

a zone where fresh water and salt water mix.

In this disorienting world,

their bodies complete the final change

for life in salt water.

But now, they encounter yet another new threat.

The Bay of Fundy, one of the most

concentrated fish farm sites in the world.

For a young salmon on its way to sea,

these fish farms can be deadly.

Food pellets sprayed into pens

rain onto the sea floor and mix with fish waste.

Caged fish are checked regularly for parasitic sea lice,

which they can attract in large numbers.

These parasites occur naturally in the wild

but proliferate around fish farms.

They can savage populations of sea trout

and migrating wild salmon.

- Wherever open net and salmon aquaculture is practiced,

wherever there is large concentrations

of these salmon farms,

wild Atlantic salmon are in serious trouble.

The industry grew and grew and grew,

and all of the wild salmon routes

that flow into the Bay of Fundy,

the wild ones decline, decline to the point that now

where once there were 40,000 wild salmon

coming back to those 30 great little rivers,

big salmon included,

now there's just a few hundred.

Probably the most significant threat

open net and salmon aquaculture

is when farm salmon escape,

and they escape in the tens of thousands,

sometimes hundreds of thousands, every single year,

and the ones that survive,

when they get the urge to spawn,

they're running up wild salmon rivers

and interbreeding with wild fish,

and just after a couple of generations,

you've got a hybrid, and the survival of those hybrids

are very very poor.

I mean, genetic changes are forever.

- [Gabriel] When Jonathan Carr isn't tagging fish,

he's checking for escaped farm salmon.

Scales show growth patterns which instantly identify

a farmed salmon.

- Hey Graham, look at that.

Graham, is it looking like a wild salmon or a farm salmon?

- Definitely an aquaculture salmon based on the scales.

- [Gabriel] Salmon aquaculture began in the 1960s,

with only a few commercial farms.

But today this industry is producing

an estimated 530 million farmed fish annually

compared to a dwindling population

of only three million wild salmon

throughout the entire North Atlantic.

- Solutions would be to regulate the industry more strictly,

make sure that there is reporting, enforcement,

and make sure that we have the very best practices.

The ultimate solution is closed containment.

And whether closed containment on land

or closed containment in the ocean

so that the fish simply can't escape.

It's a better operation for the industry

as well as for the environment and wild salmon

because the farmer controls his environment.

If there is disease,

there's no disease spread.

Everything is self-contained, no escape.

- [Gabriel] On both sides of the Atlantic,

the survivors now head into the open ocean.

An ancient genetic code compels the salmon

to migrate to the ocean,

turning north towards their distant feeding grounds.

They travel near the surface with other schooling fish,

including herring and mackerel.

Along the way, dangers abound.

Attacks come from below and above.

Easily spotted near the surface,

they're vulnerable to diving birds,

voracious blue fin tuna,

and giants from the deep.

But the presence of predators alone

cannot account for millions of salmon

disappearing each year.

There is something fundamentally different

in the ocean today.

The Celtic Explorer is setting out

from the west coast of Ireland

into the North Atlantic

on the final journey of a three year research mission.

SalSea, Salmon at Sea, is the most ambitious program

ever launched to study wild Atlantic salmon.

The scientists must discover their age old

migration pathways up to the Arctic feeding grounds

and find clues about what is happening to them

along the way.

- There are very few fish that roam as far and as wide

as the Atlantic salmon.

It ranges from the very edge of the ice fields

right down to the orange groves of northern Portugal.

- [Gabriel] Finding these tiny salmon

in the surface layers of the ocean

is a daunting task,

but the team has vital intelligence from which to work

based on known currents

and the expected migration speed of the fish.

- We wanted to know how fast the fish went

and we wanted to know the direction they went in

and what currents they used when they were moving north

through the Atlantic.

And these models have done an incredible job for us,

because not alone have they told us

the answers to those questions,

but they have delineated,

they have actually described for us and mapped for us

individual corridors where very large numbers

of salmon congregate.

- [Gabriel] Before SalSea,

almost no one had studied wild salmon in the ocean before.

Far out to sea, the Celtic Explorer is on its mission

to find the migration path.

They follow the continental shelf edge north,

where there are strong currents and a gathering of sea life.

Searching for these small fish in a vast ocean

is something that has never been attempted before.

- People have told us, well, salmon smolt at sea,

they've never seen them.

Even though I spent six years in the Arctic,

I've never seen salmon smolt,

so hopefully this is going to be something exciting.

- [Gabriel] At regular intervals they sample

near-surface ocean temperature and salinity.

The plankton net collects available food,

vital for baby salmon to continue their journey.

- The growth pattern of these fish

can actually tell us how well these fish are doing.

- [Gabriel] The surface trawl is hauled in

after hours of fishing.

- The main thing is gonna be

the fish coming through the hopper.

When they start coming in, they're gonna come in

pretty fast and furious.

So we need to sort them very quickly.

- [Gabriel] The first trawls are loaded with mackerel.

Where are the smolts?

Trawl after trawl brings in thousands of mackerel.

At last, deep among the great mass of mackerel,

they find a few young salmon.

They are immediately transferred to the lab below.

A clip from each fin provides vital DNA.

- These are very precious fish,

so really I think this is where the genetics

comes into its own.

Because they're so precious,

we want to get as much information as we can

from those fish.

This technology, this technique, the genetics,

will allow us to determine the river of origin.

- [Gabriel] The DNA samples will allow them

to trace the migration routes of salmon

from different rivers.

- When salmon go to sea, they have a great ability

to lay down in their scales

the history of their journey at sea.

And it's very much like the rings on a tree

but much more sophisticated,

because not alone does it tell us

where the fish went at sea

in terms of the chemical composition of the scale

but it also tells us how fast they grew at sea.

- [Gabriel] Scale samples from each fish

will be compared with samples taken decades earlier

to see if marine growth has declined and why.

We can look at their life histories

in the period from when they left the river

to the period that they arrived at the feeding grounds,

What was the quality of the environment?

So I think these are the kind of little

pieces of the jigsaw that we're starting to learn now

that will be incredibly valuable as we go forward.

It allows then to say something about

the conditions that are in those locations.

The plankton, the quality of the feeding.

More importantly, the quality of the fish.

Are the fish full?

Are they starving?

What's their condition?

- [Gabriel] After days of trawling and sampling,

the team has found hundreds of juvenile salmon.

Scientists can now begin to piece together

the journey to their North Atlantic feeding grounds.

Salmon from southern rivers leave first.

They are joined by other populations, river by river,

as they head north.

They arrive at the first feeding grounds.

Some salmon will return to their natal rivers after a year.

Others will continue the journey

to the feeding grounds off west Greenland.

One of the Celtic Explorer's key findings

is that many of the fish they sampled

were thin and undernourished.

The cause was distressingly clear.

In some areas Celtic Explorer's special plankton net

came up completely empty,

and the conclusion is simple and alarming.

- There's probably large scale climate forcing

mechanisms that are occurring.

Well documented changes occurring in the ocean

and the environment.

Temperatures are getting warm, it's changing current flows,

it's changing prey distribution.

- [Gabriel] The seas are changing.

The SalSea project tells us that salmon must adapt

if they are to survive.

They have already survived two ice ages,

but can they now adapt as fast

as the changing world they inhabit?

SalSea discovered an unexpected threat

facing European salmon.

Commercial fishing trawlers targeting mackerel

were right in the migration path of the young salmon.

The discovery that the trawlers were active

in these migration corridors underscores the urgent need

to create protective seasons

during which trawling would be prohibited in these waters.

Yet facing brutal odds, some salmon do reach journey's end.

Here, they encounter a very different world.

Greenland.

After a grueling journey,

the salmon that have made it this far

at last find a safe haven.

(serene music)

These cold waters are incredibly fertile,

and they feast on capelin, fish rich in oil and protein.

The salmon will feed here for two to four years,

sometimes growing to immense size.

For thousands of years, this was where they thrived.

But then, just 50 years ago,

a small band of fishermen netting off west Greenland

made a startling discovery

when they came upon the salmon's secret feeding grounds.

And word traveled fast, and soon fishing ships

from all over Europe converged here.

This remarkable footage, taken by angler

and conservationist Lee Wulff, documents the tragic tale.

- [Lee] This is a 20 knot ship, about 200 tons.

In her hold, she has 36,000 salmon

taken in a little over a month of fishing here.

Yard by yard, the 18 miles of continuous net comes aboard,

and with it come the salmon.

- [Gabriel] In 1971, their catches peeked

at nearly 800,000 salmon,

and this set the salmon on a downward spiral.

Scientists calculated that in 1972 alone

netters removed one third of all salmon

swimming off west Greenland.

Fortunately the crisis was recognized.

The following year an embargo was established

on international boats.

10 years later the North Atlantic Salmon

Conservation Organization was formed

as a formal international treaty organization

to protect the Atlantic salmon.

By the late 1980s, quotas were established,

and a decade later, Greenland has agreed not to export

any salmon.

It was a vital step in saving the species.

- Described by some as a United Nations

for the Atlantic salmon,

NASCO houses members of most North Atlantic governments

with salmon interests, and additionally,

about 40 non-government organizations

from countries all around the North Atlantic.

One of the immediate benefits of the NASCO treaty

was that it established an enormous protected zone

free of fisheries for salmon in the North Atlantic.

- Greenland is the principal feeding area.

The fishery is a problem because it harvests salmon

from all rivers.

The fishery of Greenland was where

all of the Atlantic salmon from eastern Canada and the US

congregate for a couple or three years to feed,

so that's the principal feeding area.

It's a mixed stock fishery,

so you have Atlantic salmon

from a whole bunch of different rivers

both sides of the Atlantic mingling the ocean

and there's no way for the Greenlanders

when they put a net in the ocean

to just focus their fishing pressure on a healthy population

as opposed to pulling up the nets

and maybe they have a few salmon

from the St. John River, which is threatened,

or the Penobscot River in Maine, which is threatened.

If they're going to have a fishery at any sustainable level,

you gotta think about the future of the species,

and I think they've realized over the last number of years

they've seen fewer and fewer fish,

their quotas negotiated by NASCO have been reduced

year after year after year.

The scientific advice is there should be no fisheries,

so even a very small fishery is problematic

for a lot of our salmons runs here in eastern Canada.

- [Gabriel] The Greenland quotas were a sensitive issue

for local fishermen.

Conservationist Orri Vigfusson,

in partnership with the Atlantic Salmon Federation,

began working with local fishermen

in order to reduce catches of salmon.

- 22 years ago set up the North Atlantic Salmon Fund

for the sole purpose of conserving salmon

the fastest and the most effective way,

i.e. using commerce to do this.

Actually to pay fishermen not to fish.

I buy back their fishing rights.

I have raised millions and millions of dollars this way,

mostly from the private sector.

We've been very successful in brokering

commercial agreements with the fishermen

who have voluntarily agreed not to harvest the salmon

in return for development of other employment,

other fisheries that are sustainable.

- [Gabriel] Some small scale fishing

does still happen here.

Greenlander Johannes Heiland is a traditional fisherman.

Today he will stay close to his island shore

and will fish for salmon.

His catch will only be sold in local markets.

(suspenseful music)

Close by, other fishermen net cod,

a fish that has recently rebounded.

These men are the face of Greenland fishing today.

The SalSea program has helped us to understand

the migration paths to Greenland.

But we still know very little about the return journey.

Marine biologist Tim Sheehan and his colleague

Rasmus Nygard are trying the near impossible.

To hook a large salmon in the ocean,

reel it in safely, and fit it with a satellite transmitter,

then set it free.

This is the first attempt to track the salmon migration

from Greenland waters.

(laughs)

- The ocean's really a big unknown for salmon,

and we know these kinda general trends, where they go,

they're feeding off of the coast of Greenland,

they're feeding in the Norwegian sea.

We have these kind of big picture ideas of what goes on,

but we really don't know any of the details.

These different research activities that we're undertaking,

we're really trying to fill in a lot of those pieces

and give us a much better idea as to what's going on

not only in fresh water but also in the ocean

during the salmon's life cycle.

These tags will give us a better idea

as to the routes that they're taking to migrate home,

and by tagging them at Greenland before they go home

we can look at that second half of the migration.

- [Gabriel] The pop-off tag has been designed

to stay attached to the fish for eight months.

After that time, the tag is released

and floats to the surface,

and the information it carries

is downloaded from a passing satellite.

Now for the first time,

Tim is able to trace the beginning

of the salmon's journey back from Greenland.

It is an important step in this new track.

Remarkably the fish dove far deeper

than anyone predicted, some 700 meters into the dark abyss.

- This is the first time that this has been done.

First look into the environmental conditions

that salmon are experiencing

as they're off the coast of Greenland

and as they begin their migration home.

We can start looking at some of the oceanographic conditions

and in those areas at that time, what has changed.

Start forming hypotheses as to what could be

driving the mortality that we're seeing in the ocean.

- [Gabriel] The truth is, we still know very little

about the salmon's journey home.

But we do know that the number of salmon

returning to their rivers after

their great North Atlantic migration

has dropped by 70% in the last three decades.

It is now springtime.

The great salmon that have spent years at sea

now return to the rivers of their birth,

guided in part by the distinctive scent of its waters.

Now full grown, instinct drives them

to fresh water to spawn.

But this journey too is far from easy.

In Scotland a resident pod of dolphins

awaits their annual windfall.

The strong currents in the Moray Firth

virtually deliver the salmon straight to them.

Some are taken, but many escape.

All around in North Atlantic coastlines,

the great salmon runs have begun.

A small commercial fishery operates

in Montrose Bay, Scotland,

a fourth generation family business.

George Puller is part of a deeply rooted Scottish tradition.

- Our family business was established in the late 1960s

by my father and grandfather.

At one time, there used to be netting stations

throughout Scotland almost on every part of the coastline,

but what has happened was in the late '80s,

the fish farms reduced the price of the wild salmon so much

because the customers didn't really recognize the difference

between a wild salmon and a farm salmon.

Since then the wild salmon has rallied in price,

but the netting effort now

is only about 5% of what it was in 1952.

So there's only a handful of people left in Scotland

to do this kind of work.

- [Gabriel] For centuries these small scale fisheries

were sustainable.

Now along with the declining runs,

their numbers have plummeted.

George and his family face a challenging future.

- Our fishery here started in the early 1800s,

and it's part of the fabric of Scotland,

and you know, we want it to continue

for many generations to come.

- [Gabriel] The Scottish government felt

the threat to the salmon was so severe

it recently placed a three year moratorium

on any taking of wild salmon in coastal waters.

Small fisheries are not the only communities to suffer

as salmon stocks decline.

Upriver the fabled sport of salmon angling

is changing too.

Angling for salmon is not only the fabric of Scotland,

it is the heart of life on the rivers of Ireland and Norway,

Iceland, eastern Canada.

This is no overnight sport,

but learned with lessons accumulated over a lifetime.

Atlantic salmon are already extinct

in more than 300 rivers.

Far up river the journey is almost over.

Researchers are tracking how many have survived.

The waters of the Miramichi River in Canada

were famous for enormous runs of Atlantic salmon.

Just a few decades ago,

25% of all salmon bound for North America

came to this one river alone.

100 kilometers upriver, Mark Hambrook and fellow biologists

are netting a protected pool in autumn

to count the returning fish.

The salmon have lost their silvery sheen

and changed into their striking spawning colors.

The russets and browns of autumn.

Among the few that return,

they are finding a wide variety of ages.

Some left for only one year.

Others stayed away for up to four years.

By spreading the risk over many ages,

nature ensures the species

is never brought down by one generation.

However, every year, fewer and fewer return.

These are the fortunate ones.

The concern is about those many others lost at sea.

Where once a half million adult salmon

came here to spawn each year,

now they number less than 40,000.

This is a monumental decline.

- Wild male salmon.

So many set out, so few return.

But we now know more about the salmon's incredible journey

than ever before.

As the investigators compile the data

and share their discoveries,

a complex and alarming picture emerges.

Young fish are leaving the rivers earlier than ever before,

triggered by warming waters.

Salmon are cold water fish.

- As the smolts grow, and as they grow faster,

they reach the smolt stage,

the stage when they can go to sea,

they reach that earlier.

Sometimes a year earlier than they did previously.

The fish are then small fish, but still ready to go to sea.

But those small fish, once they go to sea,

are much less fit, and really the survival rate

of these smaller fish when they go to sea

is a lot poorer than the bigger, older fish

that we had in the past.

- [Gabriel] They are challenged

even before they make it to sea.

Once at sea, the young salmon are unable

to find the food they need to grow and survive.

The plankton and larval fishes have moved north

due to the warming waters,

and salmon from southern rivers have to travel farther

and are weakened by the lack of food

and are more susceptible to predators.

Even adult salmon are finding it hard

to find their preferred food in a changing ocean,

and when they return, many are not

in optimum condition for spawning.

These findings are all linked.

The Atlantic Ocean is changing fast,

and maybe faster than salmon can adapt.

The salmon are getting lost

in the wrong place at the wrong time,

failing to find food

or encountering enemies they never knew.

Warming water lies at the heart of the mystery.

- What we now know is that climate change has impacted

directly and very severely on Atlantic salmon at sea.

Really the way it has done this

is through the temperature changes that have happened

in the surface of the oceans.

As a result of these temperature changes,

we find that the plankton is actually moving north.

Species of plankton that are comfortable

in water that is reasonably cool

now find conditions to be entirely unsuitable,

and each year they're moving further and further

and further north.

What we do know is that conditions are changing,

and always when you get a big change in an ocean

you're going to see an increase in terms of mortality,

as the fish changes and as the fish adapts.

20, 30 years ago, there would've been in the region

of seven or eight million Atlantic salmon at sea.

That's now down to about three million,

and as far as we can see it's continuing to drop.

- [Gabriel] Changing ocean conditions will require

international cooperation to protect the salmon.

We must also turn to fresh water

to make sure we have clean rivers and estuaries,

unobstructed passage, good spawning beds,

and healthy nurseries for the young

to send as many salmon out to sea as possible.

As the salmon are adapting and changing

to the new ocean conditions

we must reduce man-made pressure

to give them time to adapt.

One solution is to create protected migration corridors

from the remotest spawning beds

all the way up to the Arctic feeding grounds.

But there are some stories of hope.

People who are fighting for the species

and making a difference.

The Penobscot River in Maine was once a great salmon river

until dams blocked the way for migrating fish.

- I'm looking at a broken river that we've had here.

You know, for over 100 years we've had this dam

and then several other dams above it.

You know, we've tried to build hatcheries

to put fish in above these dams,

but we've never really addressed the problem

that there are just too many dams in this river,

and the Veazie Dam here,

this dam is at the head of the tide.

100% of the spawning grounds

for species like Atlantic salmon

are all above this dam.

These dams on the main stem river

were built back in the 1930s,

so since that time, salmon have come to these dams

and not been able to get any farther

to their spawning grounds.

Over time we've built fish ladders

that largely haven't worked.

We've had two studies in the last decade that have said

if we're gonna restore Atlantic salmon

on these big rivers in Maine like the Penobscot,

we have to reduce the number of dams.

And the Penobscot project does that.

This project will remove two big main stem dams

and bypass a third dam.

So we're addressing the root of the problem

for the first time in this river in 183 years.

- [Gabriel] In recent years, heroic measures were taken

to rescue salmon.

Lift them over the dam and release them upstream.

These are some of the last remaining Atlantic salmon

in the United States.

But today, this river is about to be restored.

The Penobscot River Restoration Trust

was formed to buy three dams on the river,

remove two of them, and build a fish pass around the third.

The first to go was the Great Works Dam,

and then the Veazie Dam was breached.

It opened up more than 1000 miles of spawning habitat.

(applauding)

- So today we celebrate

the taking down of this great dam behind us,

but you'll be seeing a whole new river here within one year.

And when you see projects like this taking place

on the Penobscot River, it inspires people to do even more.

- [Gabriel] And when a dam was removed in the nearby

Kennebec River in Maine, fisheries biologist Nate Gray

witnessed just how soon life returned.

- Because of the work that we've done here,

it's revitalized this river.

The river is a living, breathing creature.

The river herring here are the prime driver

of the marine and freshwater ecosystem interface.

The river herring are the base of that food chain.

The salmon smolt out migration

almost perfectly coincides and overlaps with

the influx of this huge biomass

of river herring going upriver.

So you have the smolts dropping out

trying to get out to the ocean

and then you have the river herring

pouring in at the same time,

and any predators like cod or haddock or you know,

halibut that are hanging out at the river mouth

are much less likely to eat a salmon smolt

because there's so many river herrings.

And the restoration of these keystone species

could very well be the tipping point

for salmon coming back to this river.

- [Gabriel] In Iceland, there's another story

where humans are making a difference.

This ancient landscape, little touched by time,

is a haven for salmon.

But there are rivers with obstacles

too high for them to overcome.

One man decided to help nature along.

- Yeah, we are now on the River Tungufljót.

It never had any salmon in the past

because you can see this big waterfall here,

it's a huge waterfall,

and the salmon were never able to run the falls,

they are simply just too high for the fish.

So what I did, I leased the river for a long period of time

and I decided to make a fish ladder into the waterfall

to enable the fish to go through the falls

after the spawning ground.

So we built the salmon ladder,

but of course there were no salmon to run the ladder

because they had never been here.

So I got some salmon start from the neighbor rivers.

So we released these 10,000 smolts

and a year later, we got 60 salmon back,

which I thought was quite unique.

That was the first salmon ever running this river.

And we took all the 60 fish

and we brought them up to the fish hatchery

and we nursed the eggs and we got another 60,000 smolts

from these fish.

And we released 60,000 smolts

and then we landed 2800 on this river, Tungufljót.

So all of a sudden we have a new salmon river in Iceland.

It's quite unique what is possible to do with nature

if you help a little bit.

- [Gabriel] And so the great journey ends where it began.

It has extended over thousands of miles

and encountered every conceivable risk.

What has made it possible was a heroic will,

the primal need to reproduce

and pass on its genetic inheritance.

But the question remains.

Will one of the oldest journeys soon come to an end?

Or will the Atlantic salmon endure

to inspire generations still to come?

(accordion music)