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Jonathan investigates huge schools of sharks right off the beach in Florida!
What are they doing??
Welcome to Jonathan Bird’s Blue World!
Every winter, large numbers of sharks gather just off the beach on Florida’s east coast,
making headlines around the world and frightening beachgoers out of the water.
What are the sharks up to?
This guy wants to find out.
Dr. Stephen Kajiura is a shark biologist.
A few years ago he joined us underwater in the Bahamas demonstrating how shark electrosensory
systems work.
But his research in Florida doesn’t involve scuba gear.
It all starts…with an airplane!
Hey hey, Dr. Kajiura!
How are you?
Good to see you man!
What are we going to do here?
We are going to go fly along the beach and count some Blacktip sharks.
And you’re the pilot?
I’m the pilot.
We fly from Miami Beach up to Jupiter with high definition cameras mounted out the window.
We will take that footage back and count all the Blacktip sharks along the way.
Are you a good pilot?
I’m a very good pilot.
Oh, let’s go man!
Dr. Kajiura has rigged cameras all over his plane, turning it into a flying shark spotting
machine!
So there are two cameras mounted in the window: still camera and 4K video camera, and the
only thing that I’m worried about is like, the airflow.
You don’t have a vibration problem with this?
When we’re flying it’s pretty slow, only about 70 knots and so we have relatively little
wind blowing across.
We do pretty well.
Huh, cool, I can’t wait to see the video!
The Cessna 172 we are flying can only hold 4 people, but that’s plenty for our early
morning shark-spotting expedition.
It’s a short taxi to the runway… and we’re off.
Then we fly low, around 500 feet, up the coast just offshore, looking for little shark-shaped
shadows in the shallows.
Wow, say that 5 times fast!
Shark-shaped shadows in the shallows!
Shark-shaped –hey!
There’s some!
Oh look at all the sharks here!
Just outside the reef line!
Good to know.
We spot a huge school of sharks, which is also recorded on the door-cam.
Dr. Kajiura makes note of the location of the school so he can return later with his
drone.
Then we hightail it back to the airport!
Woo!
Well that’s one way to see some sharks.
A pretty fun way.
Later in the day, Dr. Kajiura goes to the beach near the shark aggregation and launches
his drone.
He shoots video from a much lower altitude than he can fly in the plane, that he can
use to count the sharks.
Later we head over to Dr. Kajiura’s lab at Florida Atlantic University and review
the drone footage.
So you are starting to see them here, and then they just keep going.
That’s a lot of sharks!
This is the sort of shot I was looking at here, where you can see all these sharks,
nice and close, nice and shallow, it’s easy to see them, and they’re in large numbers.
But we can see how many sharks there are as you are zooming out like this and you get
an idea.
Holy moly!
SO this is the same sort of thing.
This is where he is going to start on the one individual and just say yeah, you can
see that’s a shark , we’re not making this up..
And you can actually see that it’s a Blacktip.
Yup, exactly.
And as you’re pulling up you can start to see how many there are in this aggregation
as they are all sort of milling around here.
And so what we’re able to do is take this 4K video back to the lab and have my student
Jordan look at it on the 4K monitor and pause, count the number of sharks, advance a little
bit, count the number of sharks , and we get an estimate of the total number within this
little transect.
And one of the reasons we are able to do this down here is if you look at the continental
shelf, see it’s pretty broad over here through the Carolinas and stuff and then right down
here it just narrows right in and that’s one of the reasons these sharks are funneling
down close to shore.
It’s because they are not being widely distributed, they are necessarily coming in tight, and
that’s why we are able to be so successful down here in Palm Beach county.
We are getting these sharks, they are basically being forced.
The next day, we follow the team out on a tagging expedition.
I don’t usually get to drive…this is weird.
We get our own boat to follow along and stay out of the way.
We cruise out of the marina and down the coast to the general location of the shark sighting.
Then the research team deploys a contraption called a drum line consisting of a baited
hook attached to a weight and a buoy.
They mark the coordinates of the drum line.
Eight point zero four nine…
Next, they move the boat and repeat the process, eventually deploying half a dozen drum lines.
Then we wait.
Down below, the sharks are investigating the yummy bait.
We don’t have to wait long, because soon the team sees one of the buoys moving.
They move in and check the line.
On the line…a Blacktip shark.
And he isn’t happy!
But he has no way of knowing that the team is not going to hurt him.
They wait for the shark to get tired and stop fighting.
In this way, it’s less likely that the shark--or the researchers--will get injured.
First they take measurements.
One twenty four!
One two four!
Then they prepare a small visual ID tag only about the size of a piece of spaghetti, which
will allow the researchers to learn a lot about this shark if it ever gets caught again.
Then they remove the hook and send the shark on his way.
After tagging half a dozen sharks, it’s time to call it a day, pull all the drum lines
and head for home.
But they leave the sharks a snack for their trouble.
So what are the sharks doing in Florida?
What has all this research revealed?
MAP The tags have shown that the sharks spend
their summers up around North Carolina, but they head south for the winter in search of
warmer water.
And the natural underwater topography of Florida forces them close to shore.
So basically the sharks go to Florida for the same reason everyone else does: to escape
winter!
SUMMARY There are a lot of ways to study marine life.
In the case of the Blacktip shark aggregations, airplanes are an unconventional but extremely
useful way to gather data.
Coupled with drones, and boats, Dr. Kajiura has learned a lot about this big shark mystery.
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