[Narrator] There is a place... on this blue planet... unlike any other... ...where ice retreated, water flowed in... and life exploded.

The first people here called it "The Dawnland"-- the place where the sun rose first.

This is the story of how we used the treasure of this place... ...founded nations... ...and devastated others.

Today, this sea within a sea is warming faster than 97% of the global ocean.

So, what happens here in the Gulf of Maine could happen everywhere, for jobs, for culture, for every living thing.

But there is a hidden strength here.

Fishers, scientists and the first people here believe answers are in the sea... ...a way forward... to strike a balance between people and nature.

It will happen here, where we face the test that will define us all... ...in this place, where the sun rises first.

[♪♪♪♪♪] For thousands of years, the Gulf of Maine was one of the richest places on earth.

36,000 square miles, stretching from Cape Cod to Nova Scotia in Canada.

A special combination of temperature, geography, and currents created an underwater Eden teeming with life.

For millennia, life in the Gulf of Maine struck a balance and thrived.

But in just a few centuries, overfishing cleared out much of its abundance.

This is the story of how we harvested this sea of plenty, built empires on its cod, and pushed this bounty to its limit.

I am worried about the future because there's less and less clams down here.

[Narrator] About how this remarkable place has suffered a thousand cuts and how the animals and people here have had to adapt... or move on.

[Elizabeth Craig] These birds live a long time and a lot has changed here, so each individual bird is experiencing that change in their lifetime.

[Narrator] Now the Gulf of Maine faces its greatest challenge.

As it warms, some species disappear as others explode.

[Brian Altvater] I never knew what a green crab was until just a few years ago.

It's something I never experienced growing up.

[Narrator] How will the gulf adapt and survive its deepest cut yet?

[♪♪♪♪♪] [♪♪♪♪♪] In spring and summer, many of the things that live in the Gulf of Maine spawn, and all those tiny offspring fill the sea... [♪♪♪♪♪] ...and then the eating begins.

Tiny gets eaten by small... small by medium... medium by large, and a lot of it gets eaten by us.

Much of this eating starts with tiny critters called "copepods".

About 30 nautical miles off of Midcoast Maine, a team of scientists is on the hunt for some of the tiniest creatures in the gulf.

Looks nice!

It's kind of warm out here!

[exhales happily] [laughs] Day in the life!

[Narrator] David Fields is a zooplankton ecologist.

-You ready?

-Ready?

He's joined by research associate Maura Niemisto.

[Fields] So shallow net first?

[Niemisto] Shallow net first, please.

[Narrator] They're here to check on the engine that drives this ecosystem-- a copepod called "calanus finmarchicus".

Copepods are tiny crustaceans.

About five of them could fit in a grain of rice.

[Fields] We're going to drop this in.

We're looking to find out the abundance and the identity of all the copepods that are down in the water column, from the bottom to the surface.

I'm just going to drop it.

[Niemisto] Yeah.

Surface, goin' down.

[Niemisto] We're searching for zooplankton, so, small animals, about a millimeter in size, that are the base of the food chain.

When we count and identify the animals we find, we'll be able to say how dense those animals are and look at how they've changed over time and space.

[Fields] There it is.

[Niemisto] Nice.

[Narrator] The first sample does not disappoint.

Dense... full of calanus.

If I was a right whale, this is where I'd be.

It's packed-filled with calanus and it really is just liquid sunshine.

[Narrator] Calanus are some of the fattiest copepods in the world.

[Fields] These are the primary food source for the right whales, but they also, in their younger stages, tend to be the food source for cod, for the shrimp, for much of the fisheries that are out there, including the lobsters.

[Narrator] Calanus may be tiny, but they number in the trillions.

[Fields] The reason why a 40-ton animal can live off of an animal that's two millimeters is because they're energy-rich.

They store a lot of fat.

And by the time winter rolls around, these animals go down to the bottom, much like what you're seeing at the bottom here.

And so you can imagine a butter layer from here to Norway of three meters thick of high-density fat animals, and these whales just coming down and scooping up that fat layer.

And to survive, they need to eat about 2000 to 3000 pounds of calanus a day.

[Narrator] So having huge numbers of calanus in the gulf is critical.

[Niemisto] Understanding the smallest scale organisms and systems and ecosystems really helps us start to understand how the world works in a way that we can't really see when we zoom out to larger-scale things.

[Narrator] It's not just about quantity, it's where these critters are hanging out, because so many in the gulf eat them... ...and those animals migrate to wherever dinner's being served.

So here we are at 30 nautical miles offshore.

All right.

You guys already hooked up?

-Yep.

-Already hooked up.

[Narrator] Once a month, David and his team get a snapshot of what's on the menu.

[Fields] The real beauty of doing these kind of measurements is in the repetition of coming out over long time periods, to try to separate out the natural variability that happens year to year, from the superimposed change that's happening due to climatic conditions, or changing climates.

Coming up!

[Narrator] The sample is a surprise.

Usually in spring and summer, calanus live in the top layer of the gulf, where they're fed on by everything from herring to whales.

By late summer, this kind of copepod typically drops to cold waters at depth and goes dormant, literally chilling out.

[Fields] Here we are now in November, and we're sampling in the upper 10 meters.

We're still finding an abundant number of calanus.

And it's unclear to me whether the animals that we're seeing up in the upper water column are because the water is warmer, or if that's just kind of their natural cycle.

[Narrator] Whatever the reason, hungry whales will go wherever they need to eat.

[Fields] As the climate gets warmer, the whales will search for those places and they'll find them.

I mean, there's no doubt about that.

But as they move into these new hunting grounds, those happen to be in shipping lanes.

They happen to be in fishing grounds that are unregulated.

[Narrator] So this tiny creature is having an outsized impact here.

These are the charismatic megafauna.

They really are.

As a group, they are such an important level in that food chain that disruptions that happen at these levels are transmitted all the way up the food chain and down the food chain.

[Narrator] As if on cue, the top of the food chain arrives... [screaming] It's like a flipper!

That's fantastic!

[Narrator] A northern right whale makes a rare appearance, trailed by pilot whales and white-sided dolphins.

[Niemisto] I think this is the second time I've ever seen them out here.

[Fields] Yeah, wow.

It's really just extraordinary.

Oh, that is so beautiful!

Unbelievable!

What a treat.

We've seen one or two whales out here in the past.

And we've certainly seen the white-sided dolphins out here and the mola molas.

But it's really a fantastic sight.

[Narrator] As the Gulf of Maine warms, these sightings are becoming less frequent because whales are moving to where the water is colder and where the food is.

Here in the gulf, it's all about the eating, and, for thousands of years, one eater topped them all, a ferocious predator that ate anything on offer, but one which you might be more familiar with as the fish in fish and chips... the codfish.

The First People in the Gulf of Maine fished cod for thousands of years, taking only what they could eat and trade.

By the 11th century, Vikings were following codfish from Scandinavia to the North Atlantic Coast of North America.

In the early 1600s, the first permanent colonists showed up.

[Mark Kurlansky] There were hundreds, maybe thousands of Europeans, fishing in these waters in the Gulf of Maine, and coming to the shore to dry and cure fish.

[Narrator] Using racks to dry fish was already a centuries-old technology and was used well past the Colonial Period.

The attraction wasn't just the sheer number of fish, it was the biology of this particular fish.

[Kurlansky] It has no fat and it is ideal for curing, for salting or drying, and before refrigeration, that was the only way you could have a commercial fish.

Live codfish is about 18% protein, so once you dry it, the percentage of protein is huge.

This is like a protein wafer.

[Narrator] Cured cod could be stockpiled for months and travel well.

Soon, this protein wafer became a staple in colonial diets up and down the Atlantic Seaboard.

By 1700, a triangle of trade between the New World, West Africa and Europe had exploded, pumping wealth into places like Boston.

Slavery was one of the ways in which you could make a lot of money, so codfish merchants wanted to get in on it, and they would sell salt cod to West Africa-- which is why it's a staple in Nigeria today-- and from that, buy slaves for the Caribbean.

[Narrator] The trade in cod cannot be disentangled from the trade in humans.

That combination of wealth and misery was a part of New England's foundation.

Cod made up more than half of all its trade and became known as "British Gold".

And the families who made fortunes from cod became known as the "Codfish Aristocracy".

[Kurlansky] By the 18th century, cod had lifted New England from a handful of starving settlers to an international economy.

[Narrator] Who soon realized that maybe they didn't need Great Britain anymore.

We learned in school how the American Revolution was about freedom.

It was about capitalism... ...and about the right to make money that was at the root of New England thinking and at the root of the American Revolution.

And a lot of that came from the ability to trade cod.

[Narrator] Trading in commodities, like timber and molasses, drove New England's economy.

And critical to the list-- slaves for cod.

This deadly, lucrative trade fueled the demand for fish, and innovative Yankees were happy to oblige.

[Kurlansky] Every innovation was applied, where possible, to catching more fish.

That's what fishermen wanted to do was catch more fish.

[Narrator] In the 17th century, an in-shore fisherman could catch 200 fish in a day.

About 300 years later, technology had changed everything and a diesel-powered trawler could pull out that fisherman's entire year's catch in a single day.

Then the world took another leap with the invention of flash-freezing food.

[Kurlansky] Freezing opened a different chapter in the international trade of food because now you could ship food everywhere.

[Narrator] Frozen fish sticks and filets became staples in homes around the world, and by the end of the 20th century, cod in the Gulf of Maine were fished to 1% of historic levels.

The gulf became a different ecosystem.

With one of their main predators largely gone in a now warmer gulf, lobster populations increased by 500% in just 30 years, resulting in a fishery that is worth more than a billion dollars a year.

Luckily for the lobster, they're harder to catch than cod... ...and they have some remarkable traits, including living upwards of 100 years and producing some 100,000 eggs.

This is prime lobster habitat.

These rock piles create nooks and crannies for lobsters of every size to hide.

Protected from predators, this is where females let loose their ultimate survival strategy... ...thousands of eggs.

Lobsters rely on the odds of hatching a ton and hoping a couple make it... ...but first, mother has to build a shelter.

She gets to work, using all ten of her legs... ...including those famous front claws.

Her burrow is like a fort.

It'll protect her from currents and predators.

Down here, it's not meet the neighbors... it's eat the neighbors.

Amazingly, she's already carried these eggs around inside her body for 9 to 12 months.

Once fertilized, the eggs are carried on the outside for another 9 to 12 months, glued to the mother's swimmerets-- appendages typically used for swimming.

A deeper burrow allows her to stand, stretch out, and fan her eggs.

This increases the water flow between the tightly-packed eggs, flushing them with cold gulf water, rich in oxygen.

After caring for them for up to a year like this, they're fully formed and ready to survive on their own.

Stretched to her full length, she vigorously flaps her swimmerets, shaking her babies out of their sacs.

Her final act as a mother... ...releasing them into the big ocean.

Every year, hundreds of millions of larval lobsters are born into the Gulf of Maine.

Very few will reach the same age as their mother.

Most won't even last three months.

Defenseless, they become food before they can get enough food.

Some that do make it that long may help this team predict the future of lobsters and their fishery.

[Curt Brown] We want to know where lobsters are settling.

Are they settling further east, further west in shallow water, in deeper water?

And the data that we're collecting gives us all of that information.

We're gonna be hauling up some heavy stuff today, so just have eyes on your feet and where the rope is at all times.

-Sound good?

-Rock and roll.

Off we go.

[Narrator] Curt Brown is a marine biologist and a commercial lobsterman.

He's part of a 35-year-long project called the "American Lobster Settlement Index", which does exactly what it sounds like-- it tracks where lobsters settle, grow, and, eventually, mature into what can be caught in the fishery.

It's spearheaded by Rick Wahle.

[Rick Wahle] I started into this game back in 1985.

There was very little understanding of where their nursery grounds were, where they first settle.

[Narrator] By counting the lobsters that settle, the thought was that they could predict how big populations would eventually be.

[Wahle] The sort of Holy Grail was to have an early-warning system, a forecasting tool that we could use to follow a cohort of newly-settled lobsters right into the commercial harvest seven or eight years later.

[Narrator] The lobster fishery once spanned North Carolina to Canada.

Warming temperatures have all but destroyed this fishery south of Cape Cod.

Warmer waters have been linked to shell disease and lower egg production.

So taking the annual census of baby lobsters has never been more important.

[Wahle] Lobsters don't live in a vacuum, and we're seeing that, right from the time they settle to the sea bed, they're dealing with all sorts of fishes, crabs, other invertebrates.

Some of them are food for other lobsters, and when they're really tiny, they're really vulnerable, so they have to find a good hiding place as soon as they settle, and stay put until they outgrow those predators.

[Narrator] The bid to build a crystal ball starts with this contraption-- a modified lobster trap baited with... rocks.

[Andrew Goode] In order for us to get a sense of what's down there, how much is down there, and their distribution, we put these collectors down here, with their preferred habitat, bring them up, and then we're able to peel this back and reveal the money within.

[Narrator] Lobsters this size make for good data, but aren't what the team is looking for.

They actually want something smaller... much smaller.

The lobsters they're really after are only a few months old... ...but surviving even that long in the Gulf of Maine is a major feat.

This larval lobster is just hours old-- about the size of a grain of rice.

No real claws yet, with few to no defenses, it is naturally buoyant, and rises to the top layer of the sea, joining other plankton, plants and animals that drift with the wind, currents, and water.

This planktonic chowder is soup for the soul for many.

Fish eat on the go, whales skim and filter, some birds bob... while others float and bob, but they all eat.

No wonder why more than 99% of these guys don't make it out alive.

So, this guy just settled as a larva earlier this summer, so he is just a few months old, but it's the counts of these guys that gives us the forecasting tool for trends in the fisheries.

[Narrator] They pick this group to count because, given their size, these lobsters were born this year.

It's the one time in their lives when they can be aged with accuracy.

[Whale] So the numbers on these young of year lobsters is really important.

This is the 2023 year class.

[Brown] Every year, Maine's coastal economy is driven by the lobster fishery, so when we see baby lobsters like this settling into our collectors, it's a very good sign for us.

This is the future of our fishery right here.

Five to eight years from now, this is what we'll be catching, so when we know what's happening year in and year out with these tiny little one-month-old lobsters, it helps me make decisions about my business going forward with this boat, with my traps, with my family, with the community.

Without that data, you're kind of making decisions blind, and that's really the importance of this type of data right here.

[Narrator] A lot of people in the Gulf of Maine depend on lobsters and this data.

And it's not just the fishermen and their families-- it's all the boat builders, the trap makers, the docks, the bait, fuel, and rope suppliers, the distributors, the restaurants, all the families supported by this one species.

That's quite a lot riding on these lobster tails.

But recently, warming water is making their futures less predictable.

[Goode] The Gulf of Maine is one of the fastest-warming large marine ecosystems on the entire planet, and the trajectory of the fishery is in question because as the Gulf of Maine warms, near-shore habitats may become too warm for settlement.

[Narrator] Shallow in-shore habitats are generally better nurseries for baby lobsters, but expecting mothers are now going further offshore to hatch in cooler, deeper waters.

There's this phenomenon called "climate velocity", where marine species will track their optimal habitats-- in this case, temperature.

As the water warms, more southern species will migrate northwards.

[Wahle] The center of gravity of lobsters is shifting northward, but not uniformly.

[Narrator] So while many lobsters are moving north, there is a curious twist in this story.

[Brown] What's very interesting is here in Southern Maine, at depth below 40, 50, 60 feet, the water is actually colder for most of the year here in Southern Maine than it is in Eastern Maine.

[Narrator] Some lobsters are moving further out to sea and down deeper.

In Eastern Maine, you have a more constant temperature top to bottom, but from May till about this time of year, until storms really mix that warmer surface water here down, bottom temperatures in Southern or Western Maine are actually colder.

Down at the bottom, we're in the sweet spot.

[Narrator] As data comes in every year, the goal is to see how changes in the gulf are affecting the way lobsters behave and to remove uncertainty for the fishery and the people who depend on it.

[♪♪♪♪♪] While the lobster fishery is still relatively healthy, families who have worked other fisheries are seeing concerning changes... ...families like the Coxes.

As the tide rolls out... [Johnny Cox] I don't roll them up.

[Narrator] ...Johnny Cox heads to work.

[Johnny Cox] Maybe I should have washed them out.

I think I'm ready.

[laughs] [Narrator] Johnny's a clammer in Jonesboro, Maine.

He and his son, Andrew, spend every day they can in these waters.

[Andrew Cox] Do you want to get in and I'll push you out?

[Johnny Cox] No, I can get it.

[Andrew Cox] All right.

[Johnny Cox] All right.

Pray, pray, pray it starts.

[starter chugging, purring to life] [Andrew Cox] Just give it to her.

There we go.

Need for speed.

[Narrator] Andrew started in the family business before he was in kindergarten.

I would say, probably five, four, following him around.

He used to leave me clams.

I would be between his legs, and he would leave me a clam or two, and I would put it in my little roller, and my roller was, like, tiny.

Then all the mud fights and all that.

Good times.

Good memories.

[Narrator] It's low tide and they're heading to a mudflat that may hold some promise.

[Johnny Cox] Clam holes!

Oh, just right here.

Put the anchor out.

[Narrator] About the size of a thumbprint, a clam hole is formed when a clam sticks its neck out to breathe and eat.

Johnny's an expert at finding them-- he's been a clammer for most of his life.

[Johnny Cox] 50 some-odd years, or more.

Too long!

[laughs] Time to go to work.

The kids that I went to school with, they didn't have this advantage.

Their job was working for A&P, or pumping gas, for a dollar and a quarter an hour, and here I had just-- in three hours, made 50 bucks.

And back then, $50 was big money.

[Narrator] Today, the soft-shell clam fishery is one of the most lucrative in Maine, just behind lobsters and baby eels.

[Andrew Cox] Oh, there's one.

[Narrator] Whether pulling by hand, or digging with a rake, Johnny and Andrew can make up to $2000 a day.

[Andrew Cox] Jonesboro has installed a 250-pound limit per tide.

Usually, I try to aim for 200 pounds, but the price is always up and down, so, right now, it's two bucks per pound.

During the summers, it can peak up to $4.00.

You can do two tides a day.

You do the math.

It adds up!

[Johnny Cox] I mean, if you want to come down here and push, then you can come home with a pretty good paycheck.

[Narrator] As good as business is, these mudflats, once full of eelgrass and algae, aren't nearly as productive as they used to be.

[Johnny Cox] In the early '70s, there was clams everywhere.

I mean, from here on in, back in the late '70s, up to the early '80s, it would be all green.

I mean, it ain't there now.

And I've questioned that-- what's changed?

Green crabs.

[Narrator] Green crabs are an invasive species found along the Gulf of Maine's coast.

As they burrow for homes and look for food, they cut up the roots of surrounding vegetation, destroying vital habitat for many other species... ...and they've landed on these shores in hordes.

[Johnny Cox] I mean, we're not talking three or four green crabs.

We're talking thousands.

So, in order for them to survive, they're eating something.

[Narrator] And clams are an easy target.

[Andrew Cox] That right there-- it's neck.

That can reach all the way up to my wrist.

And that's where some good meat is.

And that's their lifeline.

If that gets... well, there goes their lifeline, they can't eat, they can't reproduce, and they die in the mud.

I'm not saying any names.

Green crabs, maybe, you know, they come across and snip-snip.

That's a free snack for them.

So, yeah, I am kind of worried about the future because the resource is actually declining.

[Narrator] Andrew is right to be concerned.

Like locusts, green crabs have descended on this coastline, destroying everything in their path.

For decades, Maine's frigid winters kept invasive species like green crabs at bay... ...but in recent years, rising ocean temperatures have kicked the door open, and their numbers have taken off.

Picture a sci-fi movie in which aliens replicate by the hundreds.

Multiply that by a hundred, and you're getting an idea of what's taking over the Gulf of Maine-- green crabs.

On the surface, they don't seem too different from other crabs.

Eight walking legs help them scamper across the sea floor.

Large claws serve as both sword and fork.

Antennae help them navigate and process their world, mainly answering three questions-- Am I safe?

Are you a good reproductive partner?

And can I eat you?

One thing that sets green crabs apart is how aggressive they are.

They will crush and eat anything in their path-- from worms to barnacles to snails.

But what they really like to feast on?

Clams.

To protect itself, this clam has burrowed deep into the sand.

It inhales water through its neck siphon to breathe and to eat.

So, in essence, this clam needs to stick its neck out to survive... ...and this green crab knows how to go for the jugular.

Sensing danger, the clam ducks back under.

But crabs have a remarkable feature-- little hairs across their bodies and legs allow them to sense their prey.

And ten legs are no match for a young clam.

A single crab can eat up to 40 half-inch clams in a day.

Left unchecked, green crabs could obliterate the clamming industry as we know it... ...but an innovative experiment hopes to stop them.

Brian Altvater Senior is a member of the Passamaquoddy Tribe and is committed to healing the environment that's brought so much to him, his family, and his ancestors.

Approximately 14,000 years, we've been in this vicinity, and a lot of people, like, a lot of the fishermen, they go out there, like myself, whether it's clams, or fish, what have you, it's all for sustenance.

Everyone I knew growing up ate clams and fish.

You know, so... yeah, clams are very important.

And... like, you know, if you went up North to visit some of the Micmacs, or some of the Maliseet, I mean, the first thing they say is bring up some clams, bring up some scallops, you know, and stuff like that, 'cause they love that stuff, you know?

And so we say, yeah, give us a few potatoes and we'll have a deal.

[Narrator] These flats in Sipayik, Maine have always provided for Brian and his community... until recently.

[Altvater] I used to talk to a lot of the elders, and they used to tell me about the abundance of fish in the area, and shellfish, and that's all changed.

I mean, like, today, we have the green crab.

It's something I never experienced growing up.

I never knew what a green crab was until just a few years ago.

They have a voracious appetite, and the environment isn't used to having them, so a lot of the indigenous species, you know, don't have a mechanism to cope with them.

[Narrator] Searching for ways to counter the green crab invasion led to the idea of growing clams inside these boxes.

[Altvater] You know, it's just like any other garden, except it's clams down the mud flats.

[Narrator] It's a collaboration with Brian Beal, a professor of Marine Ecology at the University of Maine.

[Brian Beal] This experiment is all designed to take a look at the effects of green crabs on soft-shell clams.

So, the one-millimeter crabs are eating clams that are a half a millimeter or smaller, and there's billions of tick-size green crabs that are eating trillions of soft-shell clams.

[Narrator] Every spring, trillions of baby clams and green crabs are floating in the Gulf of Maine, and, once big enough, drop down and settle on the mudflats.

The problem is, the crabs have a size advantage.

So, the basic idea of this nursery is to plant thousands of baby clams in protective boxes.

The tight mesh lids keep them safe from green crabs and give them a few months' head start.

Once a clam gets to a certain size, it's far less vulnerable to being eaten by a green crab.

Timing is everything.

There's always a race between when clams settle versus when green crabs settle.

Green crabs are settling just about a month, typically, in most places, after the clams settle.

So, this is what we're calling an "intertidal clam nursery".

What are we doing, Shawnee?

We all set?

[Shawnee] Yeah.

[Narrator] With nursery boxes in tow, the team follows the receding tide into the mud.

So what's the trick to walking out here, Dada?

Like your cross-country ski to push your foot forward.

[Narrator] They now have to set out and secure 112 boxes, filled with nearly 37,000 baby clams, and hope a cold winter keeps crab numbers down.

[Brian Beal] There's only one thing in this state that regulates green crab populations and that's the temperature of the water.

When water temperatures are cold and we have lots of ice in the wintertime, you can't find a green crab, and that's when there's more clams than you know what to do with.

When water temperatures increase to the point that they are at now, it's hard to find a clam, but you can find many green crabs.

We're just in a place, due to climate change, where the clamming industry is in jeopardy.

If we don't do anything else, what's going to happen is that green crab populations are going to continue to grow and increase, and we can probably say so long to the soft-shell clam industry as we know it.

[Narrator] Experiments like this may be the one of the only ways to preserve the fishery and a way of life... one mud flat at a time.

[Brian Beal] This is a protein source.

This is a food.

It's also a livelihood, it's also a culture, so people should care because we would really like to have these mudflats contribute to the economy of these coastal communities like they did way back when.

[Narrator] In a few months' time, the team will know if these baby clams have a future.

Meanwhile, warming water has changed the trajectory of almost all species in the Gulf of Maine... ...including a little bird that tells us a lot about the big ocean beyond the gulf.

About six miles off the coast of New Hampshire lie White and Seavey Islands.

There's little freshwater, not much vegetation, and hardly any food.

Other than a handful of scientists in the summer, no humans call this home.

Even the lighthouse is automated.

It's basically a big pile of rocks and some bushes... ...the perfect summer home for terns.

At around 6,000 birds, it's the largest tern colony in the Gulf of Maine.

About a week old, this fragile tern chick weighs less than a chicken nugget and is just a couple of inches tall.

A spotted down coat keeps it warm and camouflaged.

In about three weeks, she'll transform from this ball of fluff into a flying bird.

To get there, she really needs one thing... ...fish.

Terns are migratory birds and travel thousands of miles every year to return to their nesting sites.

Almost 90% of the birds in the colony were born here.

It's a network, but it's not very social, because everyone in town eats a lot of the same fish... ...and every fish that comes back is fair game.

Fish get stolen... ...stolen back.

Adults steal from chicks... ...and chicks learn from adults.

In this community, no one's passive-aggressive... ...just aggressive.

These terns have adapted over millions of years to eat slender-bodied fish like sandlance and herring.

Just the right size for a chick's beak.

But as the Gulf of Maine's waters have warmed, southern fish species have migrated north, like butterfish-- a perfectly good source of protein, but the wrong shape and size.

This chick is ravenous.

If its parents can't catch it the right fish, it could end up just another statistic in Liz Craig's data.

[Elizabeth Craig] Our research on this island goes back 25 years, and over that period, we've seen ocean temperatures increase and we've also seen changes in the proportion of different fish over that time, and that includes butterfish, which is a warmer-water fish that has been in the Gulf of Maine throughout this whole period but is starting to increase as the waters here become warmer.

So, the more butterfish the birds bring back to feed their chicks, the slower the chicks grow because they're really not able to swallow most of those fish.

So we see that as a real indicator of how warming ocean and how climate change is specifically impacting these birds.

[Narrator] Not only that, terns also tell us how the planet is changing for all of us.

[Craig] They're really valuable to us as society by telling us what's going on with our oceans.

They are experiencing all the same environment that we rely on.

They're eating the same fish, they're swimming in the same waters.

So, yes, it's important that we do this work to protect the birds, but what we're learning really tells us about our own lives.

[Narrator] Getting data to track them and keep tabs on their growth requires banding many of the newborns that hatch every summer.

The team will band a total of 300 chicks this season.

[Craig] All right.

The band is 1392.

[Orena] 1392.

[Craig] 63187.

[Orena] 63187.

So the wing is 55.

[Willow] 55?

[Orena] And the weight... [Craig] 65.

[Willow] Oh, nice.

[Orena] That's a good weight.

[Craig] So what we're looking at here, these-- what we call "pin feathers"-- they're going to turn into the flight feathers of the bird.

We're looking at the length of these and also their developmental stage in order to figure out how old this bird is.

So, as a group, we've decided it's probably about 10 days old.

It's a good bird.

I'm very pleasantly surprised.

[Orena] It's a healthy bird.

[Narrator] It's a surprise because they're finding that many of the newborns aren't doing as well... because the catch is changing.

[Orena] So, this is a butterfish.

It's a lot wider than a herring.

So, from the surface, if you see it in the water like this, it might look like a normal fish, but then when an adult picks it up, it turns out to be really wide, and then the chick has trouble swallowing it.

[Narrator] Liz and her team can also learn from these birds without seeing them.

They use tiny GPS tags to track the birds on their migrations.

The data reveals a remarkable journey, adding to the bigger picture here in the Gulf of Maine and beyond.

After departing the Isles of Shoals in late-August, with a quick pit stop in Cape Cod, this bird made a week-long, non-stop, roughly 2000-mile flight down to Venezuela, averaging about 200 miles per day.

That's a lot for this little birdie.

It wintered in Brazil for eight well-earned months, and in spring, came back to the Shoals to do it all over again.

[Craig] It's exciting when you get to see a bird that's come back here, and it's 20 years old-- 19, 20, 21 years old-- and it's been coming back here year after year.

And you get to know that individual-- and "Oh, it's back again this year."

To me, that's the best feeling.

[Narrator] Soon, these birds will head south and the islands will go quiet.

[Craig] We're going to back off from this bird so it can find its home.

Some of them are adapting better than others.

We see some terns bring back no butterfish at all for their chicks.

There will be more butterfish in the environment, but that doesn't necessarily mean that these birds are doomed to eat butterfish forever.

They have the capacity to learn.

[Narrator] As waters continue to warm, everything in the gulf will need to learn and adapt... Gotta love our little landing down here-- all natural.

[Narrator] ...something that the Cox family knows all too well.

[starter purring] [Andrew Cox] Nothing fancy.

[Narrator] Folks along the Gulf of Maine have been piecing life together seasonally for years-- an early version of the gig economy.

Winter might be scallops, spring, lobsters, and clamming year-round-- if you can keep the green crabs in check.

[Johnny Cox] Yeah, Harold is up on the top, waiting for a ride.

[Andrew Cox] Yeah.

Climb aboard.

I thought I would sit this one out.

[Andrew Cox] Oh, yeah?

Retirement again?

[Narrator] Johnny and Andrew have had success lobstering, but lately, something's off.

[Andrew Cox] Every yellow dot is where my traps used to be.

I've moved a lot this year.

I got a lot of dots.

[laughs] I've been trying to chase them.

No one home.

[Johnny Cox] I guess they didn't like the menu.

Crabs and junk!

[Andrew Cox] All right.

Set her up!

When I was a kid, we used to get a bucket, two buckets of, like, lobsters, easy.

Now, up in here, you would be lucky to get maybe three or four lobsters.

It could be both the warming water from climate change and it could be another factor-- the green crabs invasive species that we introduced to our waters.

All those factors are impacting our natural resources.

Yeah, that's what I was afraid of.

Green crabs.

This is the invasive species that eats everything.

[Johnny Cox] It's a problem!

I mean, they're going to eat anything.

If you take a small lobster, they'll eat it.

They ain't got no choice in the menu.

They got to eat something.

[Andrew Cox] That's out of three traps.

That's what is eating our stuff.

One.

[Johnny Cox] Well, we're gaining.

We caught enough for supper anyway.

[Narrator] Being able to roll with change is a must if you live on the Gulf of Maine.

Working these waters isn't just about making a living, it's a way of life.

[Andrew Cox] I did go to college for four years.

I loved it.

But I really enjoy this.

I have a lot invested in this, as you can tell-- these traps, the boat...

I've spent a lot of time on this water, learning the tides, where the certain rocks are, reefs.

I learned the hard way a few times.

But no, I love it out here.

Especially days like today.

Nice and calm.

Nothing's broken down.

It's not a job sometimes when you enjoy it.

Plus, I get to spend time with the old man.

[Narrator] But there's a growing fear that green crabs bring more change than any fishery can handle, whether it's lobsters or clams.

Back in Sipayik four months later, the clam gardeners are checking on their seedlings.

[Beal] Okay, so we're just hauling it right up.

[Narrator] Their clam seeds have been watered by nearly 300 tides and they hope that they've at least doubled in size.

[Beal] All right, so these are ready to come out.

Thanks, Thomas.

[Narrator] This all comes down to timing.

By setting the boxes out after green crabs are too big to fit through the mesh cover, they have a shot at turning this mudflat back into a clamflat.

[Beal] In the early '40s, up to the early '50s, clams used to be the king.

They used to be more important economically than lobsters.

But the problem is that soft-shell clam landings in Maine are at historic lows.

It's 2023 and the state has never seen landings this low before.

There's not enough to sustain a fishery.

[Narrator] Within the past 50 years, clam landings-- that's the total weight of clams brought in by commercial clammers every year-- have dropped almost 90%... ...and the clammers digging them out?

Three out of four have left the flats entirely for other work.

Brian Altvater knows that planting clam seeds may be one of their only ways forward.

[Altvater] So we got these nets, and so there's 4,000 clams in each one of these plots.

Well, you've got 50 plots, 4,000, you know, each, so you do the math.

If this turns out the way we're hoping, we'll have a crop of clams every year.

[Narrator] And they're about to find out.

So I'm just scooping the mud.

We've got 111 more boxes to do this morning.

This should have green crabs in it, but it doesn't, so I'm happy, yeah.

[Narrator] They got their timing right.

The garden boxes worked and they now have more than 100,000 seeds to plant.

For the next five months, the seeds are kept indoors.

[Beal] Goodbye!

[Narrator] Come spring, it's finally planting season.

Now twice as big, the clam seeds are going in for the last time.

And like any garden, it takes a lot of tending.

So we have 125 different plots.

All of them have 4,000 seed in each plot, so 500,000 clams that we have planted over a three-year span.

[Narrator] Erik Francis is the steward of the Sipayik Community Clam Garden.

He doesn't have to water anything, but there is plenty of weeding to do.

[Erik Francis] It is similar to any garden on land.

Any garden takes a lot of hard work.

We spend a lot of time out here, mainly moving seaweed, just to prevent the nets from being covered.

[Narrator] A covered net could lead to a ripped net.

[Francis] This is the rip caused by a storm, which left the whole net exposed, so green crab could climb under.

That's a buffet in there.

So what we're gonna do is we're going to take the net, and unseat it, and replace it.

The green crab are moving with that tide, so we have to move relatively quick to put this net down to protect all these clams.

[Narrator] No staking required here, a simple trench and backfill can keep a net down for about a year.

And while the clams grow, Erik also tracks public enemy number one.

We got some crab.

Now, what this one is, is she's an egg-bearing female.

Every little dot and speck is a future green crab.

She's carrying upwards to 100,000 plus eggs.

So she's the main reason that we have all the nets.

But this is just nature.

We're all just surviving at the end of the day.

So they're doing what they're supposed to do.

We're going to try to do what we do to have something to pass down to the next generation.

[Narrator] The Gulf of Maine has been changing ever since its formation thousands of years ago... ...but our role in just a couple hundred years has been profound... altering the foodchain and even ocean currents.

Its warmer waters now determine who thrives and who moves on.

[Fields] These things have been honed for hundreds of thousands of years to make the ecology of this animal work, and it can adapt to change, but when you make change really fast, the populations can't keep up, and they either end up going extinct, or having drastic moves to the North or the South.

[Brown] There's going to be ups and downs in any fishery.

What you want to watch out for is overharvesting, resulting in recruitment failure, resulting in lower catches, resulting in a crashed fishery.

If we were to see a major downturn, we would know about it well in advance, and so that's really the power of this project up and down the coast.

[Narrator] So paying attention to these animals may reveal clues of what's to come.

[Craig] They definitely are similar to the canary in the coal mine.

So what we learn from these birds tells us a lot of what's happening to the fish communities, which are commercially important to us here in the Gulf of Maine, as well as just the overall health of our ocean systems.

[Narrator] The ingenuity that decimated some species is now leveraged to save jobs and culture...

The clamming industry is in jeopardy and what we're trying to do is something that communities can grow their clams, protect them from green crabs, and then harvest them.

[Narrator] ...and maybe the wisdom of 14,000 years can guide us through the most profound changes.

[Altvater] We've always taken care of the land and the sea.

It has sustained us, it's taken care of us, and we'll get back to taking care of even the mudflats, and they'll take care of us.

Take care of the fish, the fish will feed us.

And the clams can be the same way-- take care of them, they'll take care of us.

[♪♪♪♪♪]