This time on Jonathan Bird’s Blue World, sharks that hide from fish?
Hi, I’m Jonathan Bird and welcome to my world!
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 War 2, 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.
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 an otherwise featureless sea floor.
The wrecks are engulfed in schools of thousands of fish.
But the wrecks of the Graveyard have also attracted something else.
It’s 6 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.
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.
Eighty feet down, the Spar is sitting upright, at a jaunty angle, with that classic shipwreck
look.
The wrecks are far enough offshore that they are 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 is no shortage of fish—huge schools of Tomtate grunts swarm
around the wreck.
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.
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.
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 are unlikely to become shark food.
But the jacks would make a much better lunch for the shark, so they give the shark a wide
berth.
The scad are using the sharks as bodyguards.
Unfortunately for the sharks, nobody asked them if they wanted to be bodyguards.
It doesn’t seem like there is much they can do about it though.
But, the sharks have figured out how they can hide from the fish.
They take turns slipping inside the wreck.
Down here, the scad seem to relax a bit, and they don’t cling quite so close to the shark.
The shark seems like she is 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 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 fisherman 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 away 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 are not cutting teeth.
Sand Tigers don’t take 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.