♪♪ NARRATOR:
In 2013, the Caribbean Sea gave up an extraordinary secret. It was a vast,
pristine coral reef rising up from the Caribbean's
deepest waters. It was the discovery
of a whole new world. PETERSEN: It's just humongous. It's like a medieval fortress,
like big and robust. HEYMAN:
I have never seen any place with the kind of
live coral cover, the density of fish.
It was so magic. NARRATOR: But once discovered, the challenge was how to keep
this underwater Eden safe and how to learn from it. HEYMAN: I realized we needed
to research it, learn more about it,
understand it better. But we needed to keep it quiet. NARRATOR: And so began an
undercover scientific adventure, a dive into a living treasure
whose secrets may hold the keys to saving many
other reefs in trouble. ♪♪ ♪♪ ♪♪ ♪♪ NARRATOR: Fishermen are known
for tall tales, but this one is true. ♪♪ ♪♪ It begins in May 2013,
when a fisher from Guatemala is pushed into
an act of desperation. ♪♪ The big fish he depends on -- the groupers, snappers,
and jacks -- have virtually vanished from waters that
once teemed with life. ♪♪ ♪♪ He takes a dangerous gambit and pushes farther and farther
into the open ocean. ♪♪ ♪♪ As the sun rises, his engine
struggles under the strain. [ Motor sputters ] ♪♪ ♪♪ Miles from land, the water
is unexpectedly shallow. ♪♪ Just beneath the swell, a massive crown of rock
and coral rises up -- an uncharted,
undiscovered reef. ♪♪ It's a tantalizing treasure, a Caribbean secret
that will raise hopes for the survival
of coral reefs everywhere. ♪♪ The fisher tells only
a handful of people. Ana Giró, Kenny Martin,
and Dr. Melanie McField have spent years
studying Caribbean corals. Ana is among the first to hear. PETERSEN: So, this fisherman
comes up to me, and he told me about some rocks. And so I told him,
"Well, take me there. You know,
I want to see the rocks that you --
that you're telling me." ♪♪ ♪♪ It's just humongous. ♪♪ It's like a medieval fortress,
like, just big and robust. ♪♪ We have pinnacles that come out. ♪♪ Deep walls. And then,
incredible barrel sponges. ♪♪ It's just mesmerizing. ♪♪ ♪♪ ♪♪ NARRATOR: This newfound reef
is a stunning contrast to many other Caribbean reefs
that are in peril. ♪♪ It's like stepping back in time
to when all reefs were thriving. ♪♪ PETERSEN:
There are shallow reefs, vibrant and beautiful
and different kinds of fish. The ecosystem is just
so diverse, many types
of different communities that compose this
incredible system. ♪♪ That was just
an incredible experience for me, you know, personally. ♪♪ McFIELD: When Ana told me
she found this new reef, that it's just totally amazing, I believed it,
but I wanted to see it. We have benthic habitat maps.
It's not there. It's not there, you know,
when you look on Google Earth, You know,
we saw nothing on our maps. ♪♪ NARRATOR: By 2017, the reef's significance
is starting to emerge. It's an underwater mountaintop
bigger than Manhattan, crowned with coral and set on
the edge of the Cayman Trench, the deepest part
of the Caribbean. It became known
as the Cayman Crown. It's part of
a Mesoamerican Reef system straddling the waters
of Belize and Guatemala. ♪♪ News of the coral wonder is quietly shared with fisheries
expert Dr. Will HEYMAN. HEYMAN: I was at a meeting
and somebody came up to me and told me
this incredible story of a place
that nobody knew about. There's giant, giant fleets
of ships that go through here supplying the country
of Guatemala, the country of Honduras. But when you check it out,
you zoom in, you look at it, all the ships are going this way
or they're going this way. There's a shallow area right between these two massive
shipping routes, and that's the Cayman Crown.
It's hiding in plain sight. What I heard was these were some of the healthiest
coral reefs in the world. I have never seen any place with
the kind of live coral cover, the density of fish.
It was so magic. I realized we needed
to research it, learn more about it,
understand it better, but we needed to keep it quiet. NARRATOR: To build the
scientific case for protecting the Crown,
the team works quietly. If news got out, fishers might
be tempted to target the reef. PETERSEN:
So, we kept it a secret. So research, the explorations,
and everything, kind of just between
a selected group of people. Before we have it,
like, protected, that was, you know,
our main -- our main goal. NARRATOR: But protection will
only be possible with the support
of local fishers. The team invites Kenny Martin
into the circle of trust. MARTIN: We grew up
from a fishing family in a coastal community catching fish on hand lines,
and we used to use gillnets. It has caused a negative impact, and I've seen it
now that I go out scuba diving. NARRATOR: Kenny wants
to protect the fish that many people depend on. That means protecting the reef. MARTIN: ...1, go. NARRATOR:
Without a healthy reef, there will be no fish to catch. ♪♪ A coral reef
is a complex web of life, and different animal and plant
species have different roles. ♪♪ Deep gullies lead to an
extraordinary coral city. ♪♪ The inhabitants are strange
and beautiful and dependent
on one another. ♪♪ Parts of the reefscape
can feel almost industrial. The chimney of a single sponge can filter 2,500 gallons
of water a day. There are nurseries
for raising young. And dormitories
for the night shift. ♪♪ Everything is interconnected. At fish grooming stations, spritely cleaners pick off
parasites like sea lice. The reef is also home
to giant predators, like this 400-pound
goliath grouper. The gutsy little cleaner
is not intimidated. There are visitors. A pod of dolphins
feeds around the reef. [ Dolphins squeaking ] Whale sharks,
the biggest fish on the planet, gorge on an abundance of
tiny zooplankton and fish eggs. ♪♪ Nurse sharks thrive here, too. ♪♪ In a healthy system, predators only take
a proportion of their prey. If the balance is right, the number of predators
and prey can be impressive. ♪♪ Predators, like jacks,
snappers, and groupers, are vital to the health
of the reef and a key food
for local people. ♪♪ Most prized by fishers
is the Nassau grouper. Nassau groupers were once the
backbone of the local economy, but now they are
critically endangered. ♪♪ Groupers hunt at dawn and dusk. They lie in ambush
for small fishes in the reef's darker recesses. The Nassau grouper,
like everything here, depends on a healthy,
balanced system. ♪♪ The food web that feeds
the groupers starts with sunlight
and nutrients. Currents sweep
in microscopic life that's harvested by fan corals
and soft corals. ♪♪ Feather duster worms unfurl to
collect the invisible morsels. ♪♪ The next level up are grazers, nibbling algae off coral
and sponges. ♪♪ French angelfish enjoy a side
of sponge with their algae. ♪♪ Parrotfish tend
the coral garden. ♪♪ Porkfish forage
for mollusks and worms. ♪♪ Everything from microscopic
plant to predator is bound together. Spurred on by the riches,
the team has been painstakingly creating an inventory of what
lives on the reef and where. PETERSEN: It took us a long time
to explore all the reefs that we surveyed, like 90 kilometers square
of the reef. Doing monitoring
of coral-reef health and the geomorphology, and the
coral cover was incredible, like nothing that
I've ever seen before. NARRATOR: Ana photographs
the coral in strips, building a mosaic
of the richer parts of the reef. ♪♪ The photo maps reveal that
the Crown has the highest live coral cover
in the Mesoamerican Reef. McFIELD: So we can zoom in
right here. PETERSEN: Yeah,
if you zoom in right here, you know the coral composition. Coral cover, as well. McFIELD: This is the site
with 77% live coral cover? PETERSEN: Yes,
this is the site that we have. McFIELD: And you see it. PETERSEN: A huge amount
of coral cover. I mean, compared to the rest
of the Mesoamerican Reef, when we're talking about
a 19% coral cover... McFIELD:
This is the highest now. PETERSEN: This is --
yeah, this is the highest. NARRATOR: What is revealed
is a coral reef of global importance. But the team fears that
time may be running out. Caribbean waters
are warming alarmingly, posing a grave threat
to the corals. They place temperature sensors
on the Crown. McFIELD: We do have bleaching
events in the whole Caribbean, the whole world, obviously. That is probably one of the
greatest threats in this area. PETERSEN: In October,
the water is just so hot, you can feel the heat
when diving. McFIELD: 1998 was the first
global mass bleaching event, and it has gotten worse
in the last few years. ♪♪ NARRATOR:
Tucked within the stony reef are tiny coral polyps. Inside them, algae make sugars. But if it gets too hot,
the algae make toxins. ♪♪ Then the polyps eject the algae,
and the coral bleaches white. The algae can return
if the water cools soon. Otherwise, the coral often dies. ♪♪ From 2014 to 2017,
a bleaching apocalypse killed up to a third
of the world's corals. ♪♪ Amazingly, the Crown
was unscathed. But in October 2019,
tragedy strikes the region. ♪♪ The Crown takes a direct hit. ♪♪ PETERSEN:
It was completely bleached. Like, all of it.
It was just all white. HEYMAN: We saw a massive
bleaching event. I mean, the corals
that we came to know and love blanketed with snow,
it looked like. ♪♪ NARRATOR:
Then, four months later, the team notices
something extraordinary. PETERSEN:
When we go back in January, the corals get better. February, they get even better. ♪♪ May, the corals
are looking fine. They're looking beautiful. ♪♪ McFIELD: We have this
beautiful Cayman Crown Reef, and it has recovered. The corals in this region
are resilient. ♪♪ NARRATOR: The news reaches
coral expert Myles Phillips. He joins the team to investigate
the Crown's remarkable recovery. Will Heyman shares his theory. HEYMAN: Let me give you
the geographic context. So, this is
the Gulf of Honduras. PHILLIPS: Yeah.
HEYMAN: And in this channel, that's your Cayman Crown. What you got to remember is that
this is the Cayman Trench. Here, it's already
a thousand, 1,500 meters, and then drops, drops,
drops, drop, drops -- 7,600 meters, deepest point. ♪♪ NARRATOR: At its deepest, the trench is over 4 miles down. A 15-pound bowling ball
dropped in would take over an
hour and a half to hit bottom. ♪♪ Cold currents rising
from those depths sweep nutrients up to the Crown. ♪♪ HEYMAN:
This water comes slamming up onto this vertical shelf. So where we were,
those jewel reefs -- PHILLIPS:
Right at the top of it. So that's the source
of your upwelling. HEYMAN: Exactly. ♪♪ NARRATOR: The upwelling flows
along folds of rock and coral that act like pipes and channels
in a cooling system, easing temperatures
and providing nutrients. ♪♪ HEYMAN: The other factor that
we haven't talked about, we get 4 meters,
like 12 feet of rain, that falls all within a -- PHILLIPS: All in this region. HEYMAN: Through agricultural
lands, through -- PHILLIPS: Into this one bay,
through the same little channel. HEYMAN: Exactly.
PHILLIPS: So this is forming, like a -- like, a roof,
like a shade over this coral reef.
HEYMAN: That's it. NARRATOR: Just as the Caribbean
water temperature peaks, muddy water
washes over the reef. Emerging research suggests
that this runoff could shield corals
from damaging sunlight. ♪♪ HEYMAN: They're getting shade,
they're getting fed, and they're getting cooled. So where all the rest
of the Caribbean took that bleaching
and wrestled coming back, this area is resilient
because of those factors. NARRATOR: Another factor may be
the corals themselves. Myles finds an abundance
of slow-growing corals that can withstand
warming waters. He also sees a surprising amount
of faster-growing corals that proliferate like weeds
after bleaching events. PHILLIPS: Well, what I found
was lettuce coral, considered the poster child
for these weedy species that, honestly,
reproduce so quickly or so effectively that they can
quickly repopulate an area. You also had these
stress-tolerant corals that invest a lot
of metabolic energy in surviving things --
big brain corals. And they were massive
at the Cayman Crown. NARRATOR:
But what astounds Myles is something he doesn't find. A deadly disease has been
sweeping the Caribbean. To Myles' relief, the normally susceptible
pillar and brain corals seem untouched here. PHILLIPS: I saw no sign of
stony coral tissue loss disease. Actually, no sign of any disease
at all that I could see. These corals must be tens
or hundreds of years old, and they look like
they've never gone through anything in their lives.
They're completely healthy. NARRATOR: The crown
has been a sanctuary, except its isolation
has not protected it from another invader. ♪♪ It's a creature that's become
a global menace. Lionfish. They were first seen
around Belize in 2008. ♪♪ These predators from
the Indo-Pacific are among the most aggressive,
invasive species on the planet. ♪♪ ♪♪ Even the regal Nassau grouper is wary of the lionfish's
venomous spines. ♪♪ This disturbing discovery shows
that the Cayman Crown is not totally disconnected
from the outside world. The reef has trade routes. ♪♪ Fish use highways reaching
out way beyond the reef. ♪♪ The Crown, the team realizes,
could be part of a network stretching across the Caribbean
with the kind of connections that we are
just beginning to understand. But untangling these connections
has to be put on hold. [ Thunder crashes ] [ Wind howling ] [ Thunder rumbles ] [ Thunder crashes ] Hurricanes and other storms
in the Caribbean are becoming more frequent
and powerful, most likely due
to climate change. The researchers can only hope that the Crown's location
will protect it as a storm lashes
nearby shallow reefs. McFIELD: What we're seeing
in areas that are being hit over and over with the intensity
of hurricanes is that that is one of the main
causes of reef decline. And we don't have that
down here. It's very minimal. The Cayman Crown's
perfectly situated below the main hurricane belt. NARRATOR:
The Crown's exact position is yet another factor
that may make it a kind of ark, able to seed
other reefs with life. ♪♪ After the storm,
the team is back at work documenting
the Crown's inhabitants. ♪♪ Hamlets are easily
overlooked fish, but seeing the start of their
courtship brings renewed hope. ♪♪ ♪♪ They release hundreds
of microscopic eggs into the current, which sweeps them away
from the Crown's hungry mouths. ♪♪ A sea cucumber also adds eggs
into the current. ♪♪ A school of blue tangs joins
the party at a favorite parapet. The females release eggs,
the males sperm, and the eggs are fertilized. ♪♪ Currents can carry eggs
and larvae hundreds of miles, seeding reefs
from Cuba to Honduras. ♪♪ Others linger in gyres
around the crown. ♪♪ From a few days old,
larval fish can swim, guided by temperature, currents,
or maybe even sound. They are heading for the
mangroves on a nearby island. It's an in-between world
of marine trees that will serve
as their nursery. ♪♪ ♪♪ There are gangs
of pint-sized predators, like snappers and jacks,
learning the ropes. ♪♪ An inch-long barracuda lays low. ♪♪ Here's a baby cubera snapper,
a miniature version of the voracious hunter
it will become. Young wrasse go to school. And joining the class
are baby butterfly fish. ♪♪ The next stop for many young
fish is seagrass meadows. They find more food here
but have less protection than when hiding
in the mangrove roots. ♪♪ Young sardines try to avoid
run-ins with Spanish mackerel. ♪♪ ♪♪ The abundance of life
attracts nurse sharks and sting and eagle rays
that scour the shallow beds. ♪♪ The juvenile fish will set out
for new reefs when they're old enough. ♪♪ To the researchers,
the reefs, the seagrass meadows, and the mangroves make up
a trinity of life, each an essential part
of a single system. PETERSEN:
For snappers and groupers, we need to preserve all of it. We need to preserve
the mangroves. We need to preserve the seagrass
beds and the coral reefs. The connectivity
is really important. ♪♪ NARRATOR: Young fish come back
to the Crown, the hub of the system. Many fill the ranks
of grazers or cleaners, ever vigilant for predators
also coming of age, like these snappers. ♪♪ The journey to adulthood
can last several years. But snappers can live to be 80. ♪♪ Each year,
the predators aggregate at breeding grounds on the reef. ♪♪ ♪♪ Finding the location and timing
of breeding big fish is like winning the lottery
for a fisher. Spawning sites are targeted
all across the Caribbean. MARTIN: We've been seeing
a lot of fish being caught and most fish with eggs. We've noticed that,
every time you go out, you'll find less fish. NARRATOR: Kenny and Will
are searching the Crown for likely fish-breeding sites to protect the spawning
when it happens. Both believe that the Crown
must have major breeding grounds for Nassau groupers and other
species based on the currents and ideal rocky outcrops
and spurs. HEYMAN: These fish
all come together to reproduce at these very specific places
and times at elbows. This stage is promontory stage, so it's kind of like
a table corner, right? Dropping off on two sides. NARRATOR: Multiple species
can gather at a single site. HEYMAN: What blows me away about
these multi-species aggregation is, they all come
at slightly different times. They're all queued up
with the lunar cycle, with the moon,
and with the seasonal cycles. I want to understand and
characterize these aggregations. We've got to know
what's going on in order
to really protect it. NARRATOR:
Will and Kenny zero in on the most likely
outcrops and edges. HEYMAN:
I can't be there all the time, so we use remote sensing. NARRATOR: They place cameras
and microphones to collect data during the breeding season. HEYMAN: That data's
not easy to analyze. It takes time. And time is not on our side. ♪♪ NARRATOR:
They also call in an expert on grouper spawning
aggregations. Dr. Michelle Scharer
studies fish acoustics. SCHARER: My main interest is in
sound production of the fishes. They live in this environment
that is full of sound, but very few people
actually have studied that. There's an opportunity
there to learn a lot about coral-reef ecology
just by listening and not so much seeing
what's going on. Took a little bit of training
to hold your breath and actually listen when you're
down there to the sounds and the different pitches and the different rumbles
that are underwater. [ Discordant scratching ] [ Low-pitched thrum ] NARRATOR: What sounds like
a cacophony to us... [ Scraping ] ...is actually a chorus
of communication. SCHARER:
Fish can definitely hear. They have ear bones
just like we do, where they can actually sense
those vibrations in the water. [ Low-pitched thrumming ] Basically, fishes
are communicating. They are emitting signals
and receiving signals that let them know
what's going on, if they're ready to spawn. [ Thrumming ] NARRATOR: The scientists collect
an underwater recorder set up months ago. SCHARER:
We're recording 24 hours, and there's sounds accompanying
all those moments. [ Croaking ] It sounds spectacular. Just the amount and diversity and the frequencies
that we're hearing. [ Croaking ] And there's other little grunts
and beeps and boops that are different organisms
that live on the reef. So I think it sounds
pretty cool. Different species will have
different frequency bands. [ High-pitched croaking ] -Toadfish.
-Toadfish, oh! [ Laughs ] NARRATOR: Toadfish are
the noisy neighbors. Squirrelfish communicate
in clicks. [ Squirrelfish clicking ] [ Scraping ] Grunts make sound
by grinding their teeth. [ Scraping continues ] A batfish bleats. [ Batfish bleating ] Michelle has identified
fish calls used to court, defend territory,
and warn of danger. [ Low-pitched thrumming ] Nassau groupers grumpily
defend their home. [ Thrumming continues ] The calls travel long distances. [ Thrumming continues ] Listening is key to survival. SCHARER: Baby fish need to hear
where they're going and they use the sound
to guide their swimming. This helps them then
grow up on these reefs. As they grow and they need
to find where to go to spawn, they can rely on sound to find
those pathways to meet up at the spawning aggregation site
when it's time. I heard something there
different. Did you hear it, too? Yeah?
PETERSEN: Yeah, it's different. SCHARER: Okay.
There's something in here. NARRATOR: This rich soundscape
helps make the case that the Cayman Crown
must be protected. And in 2020,
science wins a big victory. The countries sharing the reef grant the Crown
conservation status. McFIELD: We've protected
this reef now. In Guatemala,
it's fully protected. In Belize,
it's highly protected. They've stepped up to the plate
and protected it. So, you know, that was
our ultimate goal, is, "Hey,
we need to protect this," and now it's happened. ♪♪ This helps, but I think
we need to now really work on management and enforcement
and do all that we can to ensure that this reef does have
all the elements that will help it be resilient and that fish are on the reef
and not being taken. ♪♪ NARRATOR: And, indeed,
the conservation win appears short-lived. ♪♪ Michelle is already
finding evidence that the Crown's future
is in jeopardy. It's spawning time, the same season Will heard
groupers two years ago. ♪♪ Now, Michel detects a shift. ♪♪ SCHARER: We did not hear as many
as we would expect. ♪♪ So I think there may be
something going on. NARRATOR: In fact,
the groupers seem to have almost disappeared
from the Crown. ♪♪ ♪♪ The news stuns the team. HEYMAN: Fishers have realized
that this is a gold mine. You know, I'm not
an emotional guy, but how do you deal with this? McFIELD: How do we stop it?
How do we stop the degradation? NARRATOR: Fishers must have been
targeting the Crown. But it's not the locals. Kenny has been working with him. He's confident they are
respecting a fishing ban the government's put in place. [ Indistinct conversations ] The team suspects the raiders are from outside
Belize and Guatemala. MARTIN: We've been seeing nets,
fishing line, even starting and batting into the reef. I've been seeing anchors
that are used to moor their boats
when they go fishing. We've been seeing
a lot of broken corals, ripped-out sponges,
and stuff like that. So we know that fishermen
are targeting it a lot for commercial species. NARRATOR: A sponge is sliced
cleanly by a fishing line. Kenny and Melanie
stitched the pieces together. ♪♪ But the team can
only do so much. ♪♪ MARTIN: I would like
to see more protection. I would like to see
patrol boats out there. I would like to see Belize,
Guatemala, and Honduras working together to protect
these resources that is very vital
to fishermen's livelihood and also for the local people. NARRATOR:
The current protections, incomplete as they are, are placing the guardians
of the reef at risk. HEYMAN: They're protecting
globally important, valuable resources
on the front line at night, you know, with people
coming out there with guns. It's dangerous.
This is protecting gold. ♪♪ [ Generator whirring ] PETERSEN: It's really alarming. You know, we need to think about
what to -- what to do. ♪♪ We need to bring back our fish. ♪♪ NARRATOR: As the team calls
for enforcement, Michelle ponders
whether groupers can be lured back to the Crown. She takes inspiration
from the marine sanctuary of Glover's Reef,
five hours north by boat. SCHARER: For a few years,
I've been collaborating with Myles Phillips,
recording the sounds of the groupers at
the northeast point of Glover's, specifically listening
to the sounds produced by the Nassau grouper to be able to detect
when they are supposed to spawn. NARRATOR:
Those recordings suggest that the groupers
are starting to gather. SCHARER: These fish have
to migrate quite a way from different distances. They need to know
they're on the right track. So communication between them
as they form little groups and move towards
the main aggregation site is really important for them. NARRATOR: Nassau groupers
are solitary most of the year. Reproduction
brings them together. Some will travel
hundreds of miles. ♪♪ ♪♪ They arrive in December
and January, when Caribbean waters
are coolest. SCHARER: They start
communicating to each other. They have different signals, different languages
or different words or vowels for the different behaviors
that they conduct only when they aggregate to spawn. NARRATOR: They also communicate
with stylized movements and shifting patterns
on their skin. HEYMAN: They look cool already. They got their stripes
and everything. But when it's getting
close to spawning, they're, like, trying on
different outfits. Some turn white,
some turn black. NARRATOR: More groupers arrive.
The chorus swells in volume. [ Loud thrumming ] ♪♪ Some wait on the sea floor,
conserving their energy. SCHARER: They need to
synchronize to 1 or 2 nights. Everybody has to have their eggs
and their sperm ready for that moment. They are communicating,
"Are we ready to spawn? Do you think we can spawn now?" [ Thrumming continues ] NARRATOR: As their numbers grow, they rise from the sea floor
each evening, as if rehearsing. [ Thrumming continues ] As the full moon approaches, the performance has become
more sophisticated. HEYMAN: Where the real fun is, is in the courtship
prior to spawning. Each has their own suite
of behaviors and sounds that all come together
into this courtship dance. [ Grouper thrums ] NARRATOR: If they are ready, they change
into matching costumes. HEYMAN: But as you get closer
to spawning, they all choose this tuxedo,
it looks like to me -- black, black, black,
with a bar over the eye, and a white belly. We call it bicolor phase. [ Grouper thrumming ] It's like a vaudeville act. Males fighting over females,
making sounds at each other. [ Thrumming continues ] NARRATOR: Males wrestle
around the females. The noise builds. [ Grouper thrumming ] But night after night,
they hold back. [ Grouper thrumming ] Then, one night,
the temperature is right. The moonlight is right. Most importantly,
there's a critical mass of fish. The chorus reaches a crescendo. [ Grouper thrumming loudly ] Then, silence. Spawning has begun. ♪♪ ♪♪ HEYMAN: These are the volcanoes
of reproduction for the entire region. All of these fish
coming all together at these promontories,
currents that are upwelling and shooting by there
and creating and captured in gyres, some shooting way long distances
to seed other places. That is the large-scale
connectivity throughout this
entire wider Caribbean basin. ♪♪ ♪♪ NARRATOR: The mating spectacle
at Glover's most likely used to take place at the Crown. Could it happen here again
with a helping hand? Michelle hatches a plan to use
sound recordings from Glover's to attract groupers
to the Crown. SCHARER: If there are fish
nearby, whatever's left, can we actually
make them recover that spawning aggregation
that once was at the jewel? HEYMAN: I'm curious.
SCHARER: How about we put out loudspeakers
and play these sounds and see if we can attract
whatever's left of what used to be
the aggregation at the jewel? HEYMAN: Okay.
SCHARER: This would be the first try to attract fish that maybe are still there,
but they've lost their cues because there's only
a few fish left. So if we play back these sounds
and they recognize them, maybe they'll come back
to the aggregation site. NARRATOR:
It's not such a wild idea. In Australia, sound recordings
were used to lure baby fish to settle on a recovering reef. Michelle and Kenny test an
underwater speaker at the Crown. The first step is to gauge
how far the sound travels. [ Grouper thrumming plays ] If the experiment works, it could jumpstart the recovery
of fisheries at the Crown. [ Grouper thrumming plays ] But recovery will also depend on staunch enforcement
of the fishing ban. [ Grouper thrumming plays ] Groupers can recover. Strict protection
of two aggregations in the Cayman Islands tripled their numbers
in under a decade. The team listens
to the grouper calls coming from the speakers below. They anticipate
what might happen. [<i> Thrumming</i> ] MARTIN: Imagine hundreds of them
coming up and "Kkkkkk," just making that thing happen. HEYMAN:
Oh, listen to that. SCHARER: I guess it takes one
first one to go off, and then everybody
follows in queue. PHILLIPS: They see one person
go to the dance, where they're like, [snaps]
"That's it." SCHARER: Mm-hmm.
HEYMAN: Yeah. [<i> Thrumming continues</i> ] ♪♪ NARRATOR: When the Crown
was discovered, it sparked a sense of hope that the Caribbean's embattled
coral reefs may not be doomed. And it has brought once unlikely
allies together. MARTIN: It's gonna be a huge
change to have fishermen thinking on a positive note
to protect these resources so they could
replenish the areas. ♪♪ NARRATOR: The team's success
in exploring and protecting
this natural wonder has given them encouragement
to carry on. McFIELD: We all get refreshed,
and our enthusiasm and our hope for
what we're doing, that it -- we can succeed and we will succeed
if we keep pushing. So that's what we do. NARRATOR: The Crown itself
has also demonstrated a remarkable resilience. And the fight for its future
has only just begun. HEYMAN:
I've seen places recover. If we're -- If we're gentle,
if we're good, if we realize the value, these places are resilient. These places can come back. And that's why I maintain hope. ♪♪ ♪♪ PHILLIPS: It's not even
a little ray of hope. This place is huge.
It's like -- It's like seeing the sun
spilling out of the clouds. ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ <i>To learn more about what you've
seen on this "Nature" program,</i> <i> visit pbs.org.</i> ♪♪ O0 C1 ♪ ♪
