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BOLINAO, Pangasinan: Marine biologist Suzanne
Licuanan leaned over the side of her battered blue and white
motorboat to collect another bag of her precious cargo—giant clam
sperm.
Holding up the bag containing
eight liters (14 pints) of the cloudy liquid, she said: “It looks
like buko (coconut) juice, doesn’t it?
The world’s largest shell fish
weighing up to 230 kilos (507 pounds) and measuring up to 1.4 meters
(4.5 feet) in length, the Tridacna gigas was once a common sight in
waters around Philippine islands.
Highly prized for its meat and
decorative shell, the giant clam had virtually disappeared from the
Philippines, fished out by local and foreign fishermen.
Shocked by the depletion of giant
clam stocks, marine biologist Edgardo Gomez decided to do something
about it.
In 1985, when he was head of what
is now the Marine Science Institute of the University of the
Philippines, he began an ambitious program to breed and restock the
bays and inlets around the Philippines, a Southeast Asian
archipelago of more than 7,000 islands.
“It really was a shock,”
Gomez told Agence France-Presse. “Giant clams are essential to
coral reefs and so it was a race against time to build stocks up.”
Licuanan joined the program
around the same time, when she was a young marine biologist taking a
four-year break in 1986 to complete her PhD on giant clams at
Australia’s James Cook University.
Married to a marine biologist who
specializes in coral reefs and with three children, she divides her
time between her work and being a wife and mother.
On this particular Saturday last
week, she was collecting sperm and eggs from clams resting on the
seabed off a small island in the Lingayen Gulf, six hours drive
northwest of Manila.
Of the 10 known species of clams
in the world, the Philippines has seven and of that number, Licuanan
said, it is the largest giant clam that is most at risk.
“Saving the giant clam has been
a long process that has involved not only breeding and restocking
but educating local fishermen that they are worth saving,” she
added.
“Clams form an integral part of
a coral reef’s ecosystem. At the same time, they can also be
farmed as a sustainable livelihood,” Licuanan said.
Already reefs and bays in many
parts of the Philippines are being restocked with mature giant clams
from the project’s protected ocean nursery areas off Bolinao in
the Lingayen Gulf.
“Sometimes you feel like an
expectant mother,” Licuanan said, tapping a syringe containing
serotonin.
“Serotonin is a
neurotransmitter that induces the clam to adduct its valves to expel
the sperm and eggs,” she explained. “Sometimes you have to give
nature a hand in these things.”
Making coral
reefs healthy
Below Licuanan’s motorboat,
divers were busy selecting 20 adult clams ranging in age from seven
to 10 years, numbered them and placed them in a circle in less than
two meters of water.
The thick shells were scrubbed
with a nylon brush before the divers returned to the boat to collect
their syringes and begin to inject the clams.
Within 15 minutes, the bivalves
started to release clouds of sperm, which was collected by the
divers in plastic bags and delivered to the boat.
The bags were bought up and less
than a liter of sperm was collected in a plastic container bearing
each clam’s number.
The rest, liters of it, was
dumped back into the sea.
Giant clams spawned through an
opening known as the excurrent siphon, which looked like a miniature
volcano on the underside of the clams.
As the clams started to spawn, a
plastic bag was placed over the outlet to collect the sperm.
Clams number eight and 13
produced nothing. Then a diver appeared calling out: “Eggs from
number 8.” Then another with: “Eggs from number 13.”
“There is a scientific method
of matching sperm to eggs,” Licuanan said as she poured the eggs
into numbered plastic bags containing sperm.
“We tend to use too little of
the sperm according to new data coming to hand,” she added.
Within two hours, the collection
was over and Licuanan was delighted with the day’s efforts.
The best part for her was that
the two clams that produced the eggs were young, only eight years
old. She said this was close to the transition stage where clams
produce both sperm and eggs.
“Clams are male when they are
young, enter a transition stage when they are around eight producing
eggs and sperm before crossing over and becoming female,” Licuanan
added.
Back at the laboratory peering
down a microscope, she estimated that they had collected about 16
million fertilized eggs.
“If 1 percent makes it past the
hatchery stage, you are doing pretty well,” Licuanan said.
“During the last clam-spawning
in May, we managed to get 12 million fertilized eggs [and] from that
we now have 200,000 clams in tanks in the hatchery measuring one
centimeter in length,” she added.
“How many of them will survive
the transfer to the ocean nursery where they will be put in cages
suspended off the ocean bed, we don’t know. It’s just up to
nature.”
--AFP
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