05x07 - Sand Tiger Sharks + Marine Biology in Turks & Caicos

[bunniefuu]

[upbeat music]

- [Announcer] This time on "Blue World,"

Jonathan travels to the Turks and Caicos

to learn how marine biologists
conduct underwater research.

But first, sharks that hide from fish.

[upbeat music continuing]

Meet Jonathan Bird,

one of the world's top underwater
nature cinematographers,

traveling the world on assignment

for all the major networks.

He is an Emmy Award-winning authority

on the underwater world.

In freshwater or salt,

reefs, wrecks, or caves,

Jonathan documents the
world beneath the waves.

Welcome to the "Blue World."

[intense music]

- [Jonathan] The huge cold
and stormy Atlantic Ocean

is known as a very
unforgiving place for ships.

But the waters off the outer
banks of North Carolina

are especially dangerous.

These rough waters with
hidden shallow shoals

have taken thousands of ships

over the past several hundred years.

Furthermore, during World w*r II,

German submarines patrolled these waters.

They snuck up on unarmed merchant ships

and torpedoed them in an effort

to disrupt American supply lines.

In a small area that came to
be known as torpedo alley,

hundreds of ships were lost.

[intense music]

Many people were rescued,

but thousands were not.

Today we call it the
graveyard of the Atlantic,

and many of the shipwrecks are accessible

to recreational scuba divers.

While there is often great loss of life

associated with a sinking
ship, life returns to the ship

as it slowly becomes the heart

of a thriving community of marine life.

A shipwreck may attract
marine life from miles around,

because it's the only
thing offering shelter

and hiding spots on another
wise featureless sea floor.

[gentle music]

The wrecks are engulfed in
schools of thousands of fish,

but the wrecks of the graveyard

have also attracted something else.

It is 6:00 AM in Atlantic
Beach, North Carolina,

and I'm boarding the dive boat Atlantis.

I'm here to explore the
shipwrecks of the graveyard

and hopefully meet some sharks.

My team and I load gear
aboard and head out as the sun

is rising ahead of us.

[bright music]

My friend, Captain Bobby Edwards has

been leading dive expeditions
here for almost 40 years.

He knows the waters and
has a feel for the wrecks.

He knows where the sharks are.

It's a two-hour run to our destination,

the wreck of the Spar.

When we arrive, I suit up.

I can't wait to get down to the wreck

and try to find some sharks.

[water splashing]


at a jaunty angle with that
classic shipwreck look.

The wrecks are far enough offshore

that they're bathed in
the warm clear water

of the Gulf Stream,
which flows like a river

from the Caribbean up the East
Coast of the United States.

And as I expected, there's
no shortage of fish.

Huge schools of tomtate
grunts swarm around the wreck.

[bright upbeat music]

The grunts are chased by jacks

which herd them like sheep

while looking for stragglers to pick off.

I see a lot of fish action, but no sharks.

Inside the wreck, not
much is happening at all.

[soft ominous music]

There's a toilet with a view.

Without finding any
sharks, our team ascends.

I have to spend a few minutes
doing a decompression stop

on the anchor line before I can surface.

We decide to try a different wreck,

so Captain Bobby moves
the boat a short distance

to the wreck of the Aeolus,
pretty famous for sharks.

[water splashing]

Soon I'm back in the water

and heading to the bottom.

Down on the wreck, the
fish action is intense.

The jacks are chasing not just the grunts,

but huge numbers of smaller
silvery fish called scad.

It's complete mayhem on the wreck

with fish darting every which
way trying to avoid the jacks,

yet still remain in the safety of schools.

Some of the schools are tightly
packed around dark objects

that are moving through the water:

sharks.

You might think that
the fish would be crazy

to hang around a shark,

but it's the perfect protection.

The scad are too small

and maneuverable to be
caught by a big shark.

As long as they steer
clear of the shark's mouth,

they're unlikely to be become shark food,

but the jacks would make a much
better lunch for the shark.

The scad are using the
sharks as bodyguards.

Nobody asked the sharks if
they wanted to be bodyguards.

It doesn't seem like there's much they

can do about it though.

[soothing upbeat music]

But the sharks have figured out

how they can hide from the fish.

They take turns slipping inside the wreck.

Down here, the scads seem to relax a bit

and they don't cling quite
so close to the shark.

The shark seems like she's taking a break

from all the excitement.

As she hovers inside the wreck,

the fish mayhem is still
taking place outside

in the background.

But that's not the most
unusual thing going on here.

This shark is hovering in place

with perfect buoyancy control.

It's extremely rare to
see a shark hovering.

Bony fish have a swim bladder they can use

to adjust their buoyancy
so they can hover in place.

Sharks have no swim bladder

and they sink if they stop swimming.

Most sharks either keep
swimming all the time

to stay up off the bottom or settle down

to rest now and then.

Hovering is just not an option.

Sand tigers, however, aren't
about to let something

like anatomy keep them from hovering.

They occasionally rise to the surface

and take a big gulp of air,

turning their stomach into
an improvised swim bladder:

perfect buoyancy.

It can't be easy to get it right,

but the sharks know just how
much air they need to gulp down

in order to hover inside
a shipwreck 90 feet deep.

This shark has a rusty fishing
hook stuck in her mouth.

Fortunately, the fishermen let her go,

but didn't want to go near
her teeth to remove the hook.

So the line was cut,

but the hook will rust in a few weeks,

leaving a rusty stain in her mouth

as evidence of the
dangers of fishing hooks.

The teeth of the sand tiger shark

are the ultimate fishing hooks.

Long, thin, and wickedly sharp,

they resemble a mouthful of needles,

pointing backwards so
nothing can wiggle out.

These teeth are superbly
designed to catch slippery fish.

But they're not cutting teeth.

Sand tigers don't take big
bites out of large prey;

they swallow smaller animals whole.

The graveyard of the
Atlantic may have begun

with the death of hundreds of ships,

but new life is springing
from these wrecks.

As artificial reefs,

they provide habitat
for fish, invertebrates,

and even sharks,

helping the ocean recover
from decades of overfishing.

Every time I visit the
wrecks of North Carolina,

I'm amazed by the experience

and astonished more than ever

by the beauty and complexity
of the "Blue World."

- [Announcer] Don't go away.

Jonathan is about to submerge
himself in marine biology.

[soft music]

- [Jonathan] It's the middle of the night

on the tropical island of South Caicos.

A group of marine biology students

are wading into a mangrove,
helping to tag baby sharks.

I'm here to observe,

to learn some of the ways

that marine biologists perform
field work for research.

I've flown to the sunny but remote island

of South Caicos in the
Turks and Caicos Islands

just southeast of the Bahamas.

Here, the School for Field Studies

operates a field research facility

where college students from
all over the United States

come for some hands-on
marine biology field work.

Faculty at the School for Field Studies

have ongoing research projects,

investigating fisheries management,

reef health, shark populations,

and even human impact on
the marine environment.

I'm going to spend some time
tagging along with the students

to see what they do every day

in their pursuit of a
degree in marine biology.

My day begins with the
shark research team,

led by Professor Aaron Henderson.

Henderson and his
students are investigating

how the marine protected areas

around South Caicos are
affecting the shark population.

Their first task for the day

is to deploy some baited camera rigs.

These rigs will hopefully attract

and film several species of sharks.

The goal?

To learn how many and what species

of sharks are here in the
marine protected area.

Some of the cameras go near shore

and others are placed in deeper water.

Later they retrieve the cameras

and search through the
footage to see what showed up.

Quite a few interesting shark species

live around the island.

Nurse sharks, Caribbean
reef sharks, tiger sharks,

lemon sharks, and even great hammerheads

have visited the cameras.

The team also tags adult sharks,

but to do that, they need to
get them close to the boat.

They use what are known as drum lines.

These are baited hooks attached
to a float and a weight.

They're designed so that sharks can swim

around when they're caught,

so they won't drown.

With five drum lines set,

the team goes back to the first
one and checks for a shark.

They check each line every 15 minutes,

so a shark doesn't stay hooked too long.

- Oh, there's something,
there's something!

- [Student] Just looking
straight up at the boat there.

- [Dr. Henderson] Okay,
let the line out as quick

as you can, Alyssa.

- [Jonathan] Soon they
have their first shark.

Dr. Henderson places a
tag on its dorsal fin

while the students take
a small tissue sample

from its tail for an isotope
analysis of the shark's diet.

While the shark team
is out tagging sharks,

another team of students is
heading out to sea as well.

This group is studying the
fish population of the island,

again, trying to determine
the effectiveness

of marine protected areas.

Instead of working from the boat,

these students will be doing
their research with scuba gear.

- [Instructor] The divers ready?

Right hand on your mask

and [indistinct] left
hand on any dangly bits.

We've got three divers going in

in three, two, one, roll.

- [Jonathan] Underwater,
they head to a nice section

of coral reef and begin a transect.

Essentially, they reel out
a very long tape measure

over the reef,

which defines a specific
path of a specific length.

They wait a few minutes
for the fish to go back

to their normal routine.

Then they slowly swim along the transect,

taking notes on what species
and numbers of fish they see.

Of course, they don't see every fish.

A lion fish hiding in a
hole escaped detection,

but this technique yields
a pretty good estimate

of fish numbers on this section of reef.

By comparing the transect results inside

and outside of the marine protected areas,

the students can learn not only

how well the marine
protected areas are working,

but on which species.

Of course, fishing pressure is

what affects fish populations,

so it makes sense to also
find out what species

of fish are being caught.

The students work with the local fishermen

who volunteer to allow
the students to come down

to the docks at the end of the
day and survey their catch.

Marine protected areas help to ensure

that there will always
be enough fish to catch.

Another team of students,
another research project.

This team is working in
snorkel depths without scuba,

studying a big snail called a conch.

The conch is one of the
most popular seafood

in the Caribbean,

and a whopping 10% of
the world's supply comes

from the tiny island of South Caicos,

so it's an important resource.

The conch population seems to be dropping,

and the conch research
team wants to know why.

This transect in the sea grass bed

is being used to count conch.

They will also collect a few conch

for additional research on land.

Back at the shore,
alongside a representative

from the Turks and Caicos
Department of Environment

and Maritime Affairs,

the students crack the conch
open in the traditional way.

Student Daniel Liu is
trying to come up with a way

to determine the size of the
shell when the shell is gone.

- Is 44.9.

- [Jonathan] Fishermen
often take the meat out

of the shell at sea

and return with only
the meat and no shell.

How can the government recommend

or enforce size regulations if
there's no shell to measure?

So Daniel's research is
looking at other ways

to gauge the maturity of
a conch without a shell.

Researchers at the
School for Field Studies

are also looking at the spotted eagle ray.

Rare in many places,

spotted eagle rays are in high
abundance in South Caicos.

Intern Connor Burke free-dives

with a camera on a pole attempting

to get close enough to do photo
identification of the rays

based on their spot patterns.

The spot patterns are unique

to each individual like fingerprints.

He hopes to identify individual animals,

learn the social structure
of eagle ray aggregations

and figure out if there's a
pattern to their movements

around the islands.

All of this information can be used

to help protect the species.

As the sun sets and the air cools down,

my day following the students isn't over.

I have rejoined with the shark team

to follow along on their night work.

Baby sharks live in the mangroves

where they're safe from a
lot of larger predators.

A couple of nights a week-

- [Dr. Henderson] Okay,
guys, come on over.

Let's get the net out there.

- [Jonathan] Dr.
Henderson and his students

head over to the mangrove
areas to catch baby sharks.

They start by setting a net
in the chest-deep water,

hoping to snare small
sharks as they cruise by.

Every 15 minutes, they check the net

and when they have a shark,

they bring it back to a
makeshift lab on shore,

where they will weigh it,

tag it with an electronic tag,

take a small tissue
sample, some ID photos,

and then quickly get it back in the water.

One of the students
will swim the baby shark

around for a few minutes
to re-oxygenate its gills,

and then they send it on its way.

From sharks to fish to
conch and more sharks,

my day with the marine biology
students in South Caicos

was exhausting but exciting.

I saw how marine biology
can be conducted from shore,

from a boat, and underwater
using scuba or snorkeling.

Sometimes we imagine marine biologists

as having glamorous
jobs working with whales

or diving with sharks,

but marine biology is a broad spectrum

of ocean related studies

with specialists in everything
from plankton growth

to whale rescues and
everything in between.

Sometimes it's pretty exciting.

Sometimes
[hitting shell]

it's not very glamorous,

but if you love the ocean
and life in the ocean,

marine biology is a job
that will never be boring.

[ending credits upbeat music]

[music ending]