Giant clams is making come back in Philippines thanks to a few dedicated scientists and co=operation of local fishermen. The giant clam, Tridacna gigas, or traditionally, pa’ua, is the largest living bivalve mollusk or shellfish and is vulnerable. One of a number of large clam species native to the shallow coral reefs of the South Pacific and Indian oceans, they can weigh more than 200 kilograms (440 pounds), measure as much as 1.2 metres (4 feet) across, and have an average lifespan in the wild of 100 years or more when we leave them alone.
The giant clams are essential to coral reefs and so it was a race against time to build stock up.
When mature, the giant clam’s mantle tissues act as a home for the single-celled dinoflagellate algae (zooxanthellae) to feed in turn it provides the food for the clam. By day, the clam opens its mantle tissue so that the algae receive the sunlight they need to photosynthesize.
Researchers helping hand
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 this southeast Asian archipelago nation of 7,000 islands.
“It really was a shock,” … “Giant clams are essential to coral reefs and so it was a race against time to build stock 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.
Suzanne Licuanan helps collecting sperm and eggs from clams resting on the seabed off a small island in the Lingayen Gulf, six hours drive northwest of Manila. This giant clam 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 says.
“Clams form an integral part of a coral reef’s ecosystem. At the same time they can also be farmed as a sustainable livelihood,” she added.
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.Back at the laboratory peering down a microscope Licunanan estimates they had collected about 16 million fertilized eggs. “If one percent make it past the hatchery stage you are doing pretty well,” she says.”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.
“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.” “Serotonin is a neurotransmitter that induces the clam to adduct its valves to expel the sperm and eggs,” she says. “Sometimes you have to give nature a hand in these things.”…”If one percent make it past the hatchery stage you are doing pretty well,” she says.”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. “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.”
Legends of the giant clam
It is told in the past that it was a killer clam or man-eating clam. Even scientists perpetrated this misinformation. Reputable scientific and technical manuals once claimed that the great mollusk had caused deaths; versions of the U.S. Navy Diving Manual even gave detailed instructions for releasing oneself from its grasp by severing the adductor muscles used to close its shell. While the giant clam does close its’ shell to defend itself, the process of closing the shell valves is so slow, far too slow to pose a serious threat to any fish or man. The clam can not suddenly snap shut on a person’s arm or leg and thus drowning them.
Sustainability and Livelihood
The giant clams as vulnerable and scientists’ help to reproduce in a safe environment. Individuals need to quit buying or eating this clam. There is concern among conservationists for the sustainability of practices among those who use the animal as a source of livelihood. The numbers in the wild have been greatly reduced by extensive over harvesting for food and the aquarium trade. On the black market, giant clam shells are sold as decoration, and the meat, in Japan, is prized as a delicacy.
Giant clam makes come back in Philippines – Staff Writers Bolinao, Philippines (AFP) Terra Daily Nov 14, ’08
Tow thumbs up award! Thanks for helping .-Mother Nature
Excerpts from http://www.terradaily.com/reports/Giant_clams_make_come_back_in_Philippines_thanks_to_science_999.html
File image. http://en.wikipedia.org/wiki/Image:Giant_clam_or_Tridacna_gigas.jpg
Excerpts from http://en.wikipedia.org/wiki/Tridacna_gigasby