You know what these are. They are steamed clams--a New England delicacy. Here in Massachusetts
we call them "steamahs" and they are delicious.
Compared to those little New England clams, this ones a monster. It weighs more than a
pound, but imagine clams even bigger than this. I heard about a giant killer clam this
big across! So I came here to an island in Micronesia right in the middle of the Pacific
Ocean. And I'm going to look for these killer clams.
The question is why do they call them killer clams? Do they eat people? Do they grab you
by the foot? I don't know so we're going to try and find out.
I have come to the middle of the Pacific Ocean to find a giant clam, more specifically known
as the Tridacna Clam.
In the Marshall Islands, people have been eating Tridacna Clams for thousands of years.
A mature Tridacna can feed quite a few people. Except for being a bit heavy, hunting these
clams isn't very hard...it's not like they can get away. So they have been over-harvested
in most of the Pacific, and finding them these days is not an easy task.
I set out to a secret place in the Marshall Islands where there are supposed some giant
clams.
Well, this is the spot so I guess now it's time to go look for some killer clams!
When I hit the water, I start to search for the clam. The reef is beautiful, with healthy
coral everywhere. This is a perfect place for a Tridacna. All I have to do is look around.
At least I see a Tridacna clam! It's grown into the reef—so it's a little hard to
see.
It responds to my hand movements. That's because it is sensitive to light and when my hand
casts a shadow on it, the clam retracts to protect itself.
This is why people thought they were dangerous. Could a clam this large actually grab my hand?
Well, let's find out. I put my hand into the clam and it closes—but the clam can't
actually close all the way. See all my fingers are still there. So much for the killer clam.
Tridacna clams live in shallow, sunlit waters. This is no coincidence, because they are solar-powered.
The clams have symbiotic algae in their tissue. The algae absorbs the energy from the sun
and turns it into energy that it shares with the clam. Without the sun, and the algae to
turn it into energy, the clam would die.
Clams also feed on plankton in the water. They have two openings, called siphons. The
clam slurps up water through the incurrent siphon, and filters the water through a sieve,
extracting the plankton. Then the water comes back out through the excurrent siphon. The
giant clam can filter hundreds gallons of water every day with this method.
Unfortunately, there isn't much plankton in clear tropical water. That's why the
clams need the algae.
These reefs would be teeming with giant clams except for the fact that they taste good—so
they have been over fished.
Here on the island of Kosrae, over-fishing of giant clams in the past has left the reefs
depleted of these incredible animals, so the solution is a clam farm!
Kosrae is known for having one of the world's few Tridacna clam farms. Here they raise hundreds
of the clams both for food, and to release into the wild.
A dozen large tanks have clams of different sizes soaking up the tropical sun. Seawater
is pumped in from the ocean. These clams make their own food from sunlight, just like plants.
All they need is a circulating water supply and time to grow.
As you might expect, they don't grow very fast.
These little clams in this tank are babies by clam standards. There're only two inches
long and eleven months old, but just to get an idea how long it takes one of these clams
to grow, If you look at the next tank, this tank has maybe five pounders. And these guys
.....Oh NO! He's got me! Just kidding! These guys are seven years old. It's pretty big.
But when you think about it-- it takes seven years for a clam to get this big. You can
see why if you over-fish these, it takes a long time for them to come back.
I'll put him down here.
So if a five pound clam takes seven years to grow, we can only imagine how old this
clam is. This hundred pound Tridacna might easily be more than fifty years old. Its three
feet across! Experts say that they may live for a hundred or more years.
So there are old clams, and they are big clams, but they're certainly not killer clams. They
sit on the bottom and collect sunlight. They're about as dangerous as sponges, but that's
a story for another day.